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ADVANCING AQUACULTURE:Fish Welfare at Slaughter

Tess Benson

Winston Churchill Memorial Trust Travel Fellow 2004

Personal background 1Acknowledgments 1Introduction 2

Fish welfare 3Achieving the aims 4

Objectives 4Planning 5Countries 6Travel 6

The Study Tour Canada 7USA 8Mexico 9Chile 10

Farmed fish species Salmon 11Trout 12Channel catfish 12Hybrid striped bass 12Sturgeon 12Tiliapia 12Arctic charr 12

Pre-harvest treatmentFood withdrawal 13Crowding 13Removal from water 14Anaesthetics 15Pumps and pipes 15Brailling 15Hand-nets 16

Killing methodsPrinciples of humane slaughter 17Staff training 17Percussive stunning 18

Priest 18Mechanical percussive systems - manual feed 19Mechanical percussive systems - automatic feed 19General considerations 20

Carbon dioxide narcosis 21 Live chilling 21Death in ice slurry 22Death in air 22Gill cut 23Electrical stunning 24

Recommendations 25The future 27Conclusions 28Advancing Aquaculture: Fish Welfare at Slaughter

Contents

Advancing Aquaculture: Fish Welfare at Slaughter 1

For the past five and half years I have been employed by the Humane SlaughterAssociation (HSA) as a Technical Officer.

The HSA is the only registered charity to specialise in the welfare of food animalsduring marketing, transport and slaughter.

As a non-campaigning organisation the HSA works in a practical and rational wayto develop welfare standards through technology transfer, education and advice toindustry and government.

The HSA uses up-to-date knowledge and practical experience to write best practiceguidelines for the industry and regularly advises retailers and others on their codesof practice. My job involves regular liaison with industry and government on animalwelfare issues and improvements.

Over the last three years I have been involved in the British aquaculture industry,gaining an understanding of the practical requirements for commercial slaughtersystems and providing advice on humane methods of slaughter appropriate to thesituation. In addition to the UK work, I have also been involved in assessingalternative slaughter methods used in Norway and New Zealand.

This work has led to production of educational material about the humane killingof fish and various articles for publication and presentations at technicalconferences.

I would like to thank the Winston Churchill Memorial Trust for its generous fundingof this study tour and its support whilst planning and carrying out this project. Inaddition thanks are given to the Humane Slaughter Association (HSA) for itssupport. Without the support of both of these organisations this trip would not havebeen possible and fish welfare at slaughter may still have been an issue on theback burner in many companies and countries. I also would like to extend my gratitude to all the people, too numerous to mention,that helped organise the study tour and spend their time detailing current industrypractices and the implications of these to fish welfare. Special thanks are given to those people who went beyond all expectations andspent many hours arranging visits and encouraging the industry to be involved inthis project. These people, in particular Melissia Struthers (CAIA), Fred Conte (UCDavis California), Antonio Campos Mendoza (University of Stirling) and AlbertoRamírez (Fundacion Chile), all made a significant contribution to the success ofthis project and also helped keep me positive (and sane!) throughout the trip.This study has been invaluable in gaining a sound understanding of slaughtersystems and the practical implications of such methods in a wide range ofcircumstances. Specific information from this study is confidential, but the knowledge from thiswork has been used to produce guidance notes on the humane killing of salmon andtrout and at the request of various parties best practice guidelines are currentlyunder development.

Acknowledgments:

Personal background

As over 30% of the global seafood harvest isalready produced from aquaculture, andpredictions made in 2000 forecast that globalfish consumption will rise 25% by 2030 (3kgincrease per person), it is easy to understandwhy aquaculture is such a rapidly expandingindustry. With such an increase in demand,new sources of cultured fish are required,especially as customers want qualityproducts all year round. In addition to this there is increasing pressureon wild fish stocks and the cost of catchingfrom the sea is rising. This cost is seen both inenvironmental and financial terms. Theenvironmental cost of the wild catch iscontinuously rising as stocks are depleted; theresultant changes in sea life affect the naturalbalance of the oceans. It is also suggested bythe FAO that the actual cost of catching wildfish can be 25% more than the value, a figurewhich is offset by government subsides. Although still a relatively new industry incommercial farming terms, aquaculture hasalready made huge changes since it becamea significant commercial venture over 30years ago. In this time the industry has grownfrom small individual farms to multi-nationalcompanies which are streamlined andincreasingly efficient at producing millions ofanimals annually. One of the primary aims of aquaculture is toproduce a consistent and safe product withfull traceability, reliably and, in accordancewith customer demands. With this aim it isclear to see how aquaculture can fit the abovedemands and help resolve the potential lackof supply, not only for food fish, but alsoimprove other industries such as those thatrely on fish, ie animal feed and leisure. As theindustry progresses, it is essential that itgrows responsibly and reacts to consumerrequirements in order to develop suitableproducts that are required.Although there is over 20 species of fishfarmed, salmon and trout are commonlyfarmed in the UK. For these reasons thesespecies have been the main focus of recent

research into humane methods of slaughterand practical improvements. However, as thenumbers of fish have increased so has thenumber of species farmed. New species arecontinuously being identified for their farmingpotential as new developments and scientificunderstanding allows production of manyspecies that were not previously economicallyviable.One of the difficulties faced by theaquaculture industry is that recommendationsare not necessarily universal or transferablebetween species or even the countriesinvolved. This makes technology transferbetween species very difficult and settingguidelines very complicated, ie what works inone country may not be legal in another ormay not even be technically feasible inanother. This means that throughout theindustry the level of knowledge varies greatly,depending on the length of time that particularspecies has been farmed. In response to the growing scientific opinionthat fish feel pain and can suffer, carefulconsideration is now being given to themethods of slaughter employed around theworld and in particular in the UK. Thesemethods are also influenced by productquality and the positive relationship this haswith humane handling and slaughter. Whilst the debate about pain perception in fishis ongoing, it is generally accepted thatfarmed fish should have their welfareprotected and be treated humanely whilst keptin aquaculture systems. The consideration ofwelfare is not only ethically correct, butcommercially sound: humane treatment isimportant to realise potential growth rates andproduct quality. Although terrestrial animalwelfare has been studied for many years,similar studies for aquaculture are still in theirinfancy. However, over the past few years theaquaculture industry has actively striven toadvance this knowledge base; supportingboth scientific and practical research whichhas led to improved technology, knowledgeand production procedures.

Introduction


The welfare of an animal can be defined as 'itsstate as regards its attempts to cope with itsenvironment'. This environment includesphysical conditions, social influences,predators, parasites or pathogens interactingwith individual animals. Fish maintain aconstant internal environment; when this isthreatened a range of reactions take place toelicit physiological (production of adrenaline,noradrenaline and cortisol) and physical(increased heart rate, vigorous musclecontractions) changes to reinstate the balanceas soon as possible; this is widely known asthe stress response. When the response issuccessful the physiological reactions subsideand the internal environment is restored withinhours. However, if the challenge is notremoved/avoided the response is prolongedand it can be assumed that the welfare of thatanimal is compromised.

In-depth knowledge of species-specificwelfare requirements and relevant signs ofthe stress response are essential for correctwelfare assessment. As a result, welfare isoften reviewed using the five freedomsprinciple which take into account thepsychological needs in addition to thephysical. These include, freedom from:hunger and thirst; discomfort; pain, injury anddisease; fear and distress, and freedom toexpress normal behaviour.

Whilst some principles for basic requirementsand responses are applicable to all speciesand transferable, there are also importantspecies differences. Every species needs tobe considered on an individual basis.

Consideration of the nature of the welfare'problem', its duration and effect on individualanimals must be taken into account duringwelfare assessments. Fish have the capacity,within limits, to adapt to acute stressors;however, exposure to chronic stressors, or anumber of acute stressors simultaneously orfor sustained periods, can lead to suppressionof the immune system if occurring during

production, or can lead to use of energystores and changes in hormones which willhave resultant effects on fish quality.

In 1996 the Farm Animal Welfare Council(FAWC) reviewed farmed fish welfare in theUK and made a number of recommendations,including improvements at slaughter. As aresult, government funding was madeavailable in the UK for research into improvedslaughter methods. Nine years on, both thesalmon and trout industries havecommercially viable, humane slaughtersystems available to them. This followsconsiderable research and co-operationwithin the industry to review the methodsavailable and to develop those most suitable.

As a result, humane methods of slaughter arenow employed widely in both the salmon andtrout industry in the UK and further afield.These methods include new generation, flow-through percussive stunners and improvedelectrical systems. The main advantage ofboth systems is the fact that fish are kept inwater right up to the point of slaughter and inboth cases rendered immediately insensiblewith little if any contact with humans whilstconscious. As it is known that handling of fishprior to slaughter can have a detrimentaleffect on the flesh quality, this also has animpact on the final product.

As the number of species in aquaculture isgrowing, so is the need for new developmentsto cater for these novel species.

Another major constraint is the growingconflict between the emerging aquacultureindustry and other stakeholders such astraditional fishers, property developers, touristboards, recreational organisations and theconservation movement.

Introduction


Fish Welfare

This study tour was undertaken to investigatethe attitudes of industry, government andresearch bodies towards farmed fish welfareand to discover international practices forslaughter. Four countries in North and SouthAmerica were included in the tour: the USA,Canada, Mexico and Chile. These countries were chosen to represent:

some of the major salmonid producersdifferent levels of economic input intoaquaculturedifferent species scientists working in the field ofconsciousness and pain perception infish

The initial aims of the trip were to: investigate welfare practices andstandards in various countriesunderstand the reasons behind thechoices made meet key scientists working on fishwelfare help disseminate information on bestpractice, based on current scientific andpractical understanding of welfare

Every country has unique economic, culturaland practical factors which influence attitudesto, and standards of, fish welfare, therebyimpacting on national industry practices andproducts. What is acceptable varies amongstsocieties and individuals and is constantlychanging as new information comes to light.The initial aim was to develop a soundunderstanding of the aquaculture industryaround the world and gain knowledge ofissues that affect the international industry.This was done by visiting research stationsand farms in these countries and observingcurrent handling and slaughter procedures.The trip has not only identified currentpractices but has also given a good indicationof the current state of the industry, futureideas, constraints and the potential of each

country to develop high welfare standards. The project proposals also included meetingwith scientists with opposing views on thepossibilities of fish feeling pain and distress, tolearn more about the concept of pain in fish tohelp form a sound judgement on the extent ofpain and distress caused to fish during routinetransport/slaughter. Site visits were a vital part of the project andcritical to the success of the trip. These visitsallow first hand experience of what reallyhappens and highlights the practicalimplications of methods used; the financialrestrictions; and resultant product quality. In addition, visits with trade and retailorganisations and government departmentswere proposed to gain an insight into industrygoals and realistic standards for now and thefuture. However, due to the sensitive nature ofthis topic and the caution of the industry, notas many visits were achieved as wereoriginally proposed. In North America there is a number of activistgroups that use animal welfare as a tool toraise funds for their cause and damage theindustry. Likewise, environmental groupshave also focused their campaigns on theaquaculture industry. Unfortunately theseorganisations generally use negative pointsand out-of-date information to damage theimage of the industry. This has meant that theindustry has become closed and is verycautious about letting new people on site orentering into discussions about the practicesand procedures of the industry. Previous experience within the Scottishindustry has proved very open and co-operative, so it was slightly unexpected to findso much resistance elsewhere. In the UK, theHSA’s reputation for practical and realisticimprovements to animal welfare at slaughterwithin other meat producing industries hashelped the transition into aquaculture andthey have been willing to work with us, butoutside of the UK this is not the case.

Achieving the aims


Objectives

Achieving the aims

As this became an increasing problem to theplanning of the trip, references wererequested from the Scottish industry so thatpeople had a better idea of how I had workedpositively and responsibly with the industry inthe UK.

However, even with references prior planningstill proved very difficult. Many organisationswanted to meet and discuss the project,before allowing site visits. This meant thatlittle prior planning could be made andrelatively little organisation done beforearriving in the individual countries. This alsohad a knock-on effect, as it meant meetingsneeded to be arranged at short notice.

Taking heed of the advice given by theChurchill trust, planning of the tripcommenced as soon as I found out myapplication had been successful in March2004. This was over six months before the tripwas due to start but, as it soon became clear,was absolutely necessary. The study tour tookplace throughout October and November2004. During the trip meetings and visits wereorganised with over 50 people andorganisations to discuss fish welfare and itsimplications at slaughter.

During farm visits the objective was to assessthe effectiveness and efficiency of slaughterand handling procedures in terms of fishwelfare, as well as discussing the reasonswhy particular methods are chosen andothers disregarded. However, on many visitsonly visual observations could be made.Unfortunately, due to the nature of thesystems and protocols, the physical reflexeswhich indicate consciousness could not beassessed on-site and the effectiveness ofindividual systems could not be made.

Farm / processing plant visits were all of aconfidential nature, as was much of the otherwork. For these reasons photography was

restricted, if not prohibited, and I am unable inthis report to provide specific detail ofoperations so as not to identify theorganisations involved. This also means thata full list of people involved in the project hasnot been listed within this report despite theirconsiderable help.

Visits to research institutes and governmentdepartments went more according to plan,although again fewer meetings took placethen first anticipated. A good insight of thecurrent research interests of the respectivecountries and where they see the future wasgained. Regrettably the pain aspect was notdiscussed in as much detail as was planned.

One of the aims of this trip was to identify thecommon aquaculture species and theirrequirements at the point of slaughter. Variousmethods of slaughter will be discussed laterfor both the advantages and disadvantages ofthe systems used and the implications ofthese on the welfare of the fish.

As aquaculture spans from the first world tothe third, the considerations given to choice ofmethod vary vastly on the financial andtechnological requirements of each systemand the ability of each country to cope andintegrate the systems. Economics obviouslyplays a large part in the method of choice andfor these reasons the relationship betweenproduct quality and method was alsoexplored.


Achieving the aims


As previously mentioned, animal welfare inaquaculture is a relatively new and emergingissue, despite there being laws in place for theprotection of other animals for a number ofyears. The main reason for this is the differingviews of whether or not fish are sentientanimals and if they have the ability to‘perceive pain’.

As with all species, terrestrial or aquatic, painis very difficult to define and measure. Thereis still a lack of consensus about painperception, but it is agreed that fish should betreated ethically whilst kept in farmingsystems.

Any method of handling animals willcompromise them, the aim of humanesystems is to minimise this in both strengthand duration.

This report is split into different sections: thecountries visited, the species observed, andthe methods observed.

The methods are explained first by thegeneral principles of how they are effectiveand then by the practical and welfareimplications associated with them. As aconclusion, areas for improvement have beenidentified, not only by changing an entiresystem but also for improving currentpractices.

CountriesAs mentioned, four countries were visitedduring the trip. Initially Alaska was alsoincluded so that a comparison could be madebetween wild and farmed salmon. In Alaskathe farming of salmon is prohibited and all fishcaught is wild. However, the study tour planshad to be changed as it soon becameapparent from meetings held with buyers inthe UK, and industry contacts, that viewingthe Alaskan catch would prove very difficult, ifnot impossible. Wild fish are caught by individual farmers whoeach own small boats and the fishing seasonis short and variable. This meant that thelikelihood of getting to see fish being caughtwas minimal. As it became apparent that mytime could be used more efficientlyelsewhere, the decision was made to includeChile in the plans and observe the salmonindustry there.

Travel The Winston Churchill Memorial Trustgenerously funded this trip so that I couldtravel around North and South America safely. Planning the actual travel arrangements oftenproved as much of a challenge as arrangingmeetings. Fish farms are rarely on the mainroad and only I could arrive in the Californiandesert the day after a rain storm! but theseincidents all added to the experience. Imanaged to make use of practically all modesof transport in the including: planes, trains,ferries, buses and cars. Not to mention themiles I walked, not realising street systemswork slightly different outside of the UK andregularly stretched for miles. For anybodyembarking on this kind of trip, I would suggestthat you can never spend to much timeresearching time zones and distancesbetween sites - England is a very smallcountry in comparison to the rest of the world!An air miles card may also be beneficialhaving travelled nearly 25,000 miles, I wish Ihad got one!

Study tour


Canada (26 September - 15 October)The study tour started on the west coast ofCanada with a workshop on fish welfareorganised by the British Columbia Salmonindustry. The trip continued east across thecountry ending in St George, New Foundlandthree weeks later. During this time fish farms,processing plants and research stations werevisited and practices observed. In additionmeetings were held with industry bodies,government officials and research staff.

Whilst in Canada, Atlantic salmon, Pacificsalmon, sturgeon, trout, arctic charr andlobster were all observed and discussed withregard to general farming

Canada's aquaculture industry operates onthe Atlantic and Pacific coasts and onnumerous lakes in between. Even though it iswide spread, there are two major provinces,New Brunswick and British Columbia, whichare responsible for about 80% of totalproduction. Although still relatively newaquaculture is now a large-scale commercialindustry across the country. Commercialaquaculture production started in the 1970sand has rapidly expanded over the past 30years to include several salmon speciesamongst others. In addition, new species arecurrently being investigated for their potentialin aquaculture such, as cod, halibut, haddockand Arctic charr.

In terms of production, Canada produced123,924 tones in 2000. Comparatively, this isstill a relatively small production figure inworld standards, but they are the world’sfourth producer of salmonids (salmon countfor 83% of this total and trout 7 %).

The economic contribution of the aquacultureindustry is quite significant: over 5,000 peopleare involved in the industry (includingpermanent full-time employment, part-timeand seasonal casual jobs). The impact of thison the industry is quite apparent when lookingat the amount of opposition the farmers face.

For instance, in parts of the east coastaquaculture is still one of the main industriesand they seem much less affected byperceived environmental problems or othernegative impacts. However, on the west coasttourism plays an important part in theeconomy and they appear to be in a moredifficult position due to the environmentalorganisation focusing their efforts in thesehigh profile areas. Canada is a significant salmonid producerand uses a variety of different slaughtermethods. These methods range from low-techmethods, such as ice slurry for trout, to someof the most advanced systems currently inoperation in the world. During my time inCanada I was allowed enough access to gaina practical insight into salmon and troutfarming. In addition to reviewing currentresearch priorities and government attitudesthe Canadians are currently faced with bigenvironmental problems and welfare is not themajor focal point. However, many companieswere running humane systems and they hadalready seen beneficial quality improvements,making the expenditure worthwhile. Manyparts of the salmon industry were beingproactive, with some provinces making movesto instigate welfare standards and nationalorganisations introducing standards also. The main obstacle to implementing humanestandards to the entire Canadian industry isthe common use of carbon dioxide stunningand ice slurry systems and low tech wellboats.It’s acknowledged this will not change quickly,but support should be given to move awayfrom these procedures in a realistic timeframe. Other food animal production industries inCanada have made mention of welfarestandards in quality programs and it was feltthat this could possibly be the way forward tointroduce welfare in a sensible way, withoutcausing too many problems to the industry.

Study tour


The USA (15 October - 23 October)My two-week stay in the USA started inItheca, New York and continued south to WestVirginia and Washington DC. The secondweek was spent in California; starting inSacramento and ending in the Californiandesert. During these two weeks in the USA I visitedfish farms and research institutes, and spokewith government workers and other industrymembers. Species observed included hybridstriped bass, catfish, tiliapia and trout. In the USA there is still a large deficit betweenthe amount of fish consumed and the amountproduced. However the development of arobust aquaculture industry has the potentialto fill this gap. Like Canada, the industry isgrowing, albeit at a slightly slower rate. Overseveral years there has been slow butcontinuous growth in domestic aquacultureproduction. Catfish production is the largestsector in the US aquaculture industry,concentrated in Mississippi, Alabama,Arkansas and Louisiana. Other major speciesfarmed for food are trout, tilapia, hybrid stripedbass. In the US as a whole, fisheries are far lessthan 1% of the economic activity, but in manycoastal areas, fisheries constitute a major, oreven the principal economic base. The main reason for visiting the US was tomeet with a range of scientists to discuss theconcept of perception of pain in fish. Over thepast couple of years, a number of papershave been published in this area and I wantedto investigate arguments for both sides withthese people. Unfortunately, due to conflictingschedules it was not possible to meet up withsome of the key scientists involved. However,those that were met provided a valuableinsight into this area and if nothing elsehighlighted the complexity of this concept andthat conclusions will not be made in theimmediate future. Busy schedules also resulted in a few of theproposed visits to be cancelled at the lastminute. A number of alternatives werearranged and various bodies and farms werevisited. A wide range of information from

various research and government officialswas also provided. The USA was the most sensitive country togaining access as there is a very activeorganisation which campaigns for animalrights. Unfortunately, due to their negativecampaigning many producers now have anegative view towards welfare. This meansthat many producers are not open to theconcept of fish welfare, even though there isevidence for significant productionimprovements. This is also reflected in thegovernment research programmes, fundingschemes which focus on post-harvestprocesses to maintain and improve qualityand shelf life – there was little interest in whatcould be done before harvest. The US industry is under significant pressureto produce food cheaply and, unlike othercountries, it appears there is little pressurefrom retailer groups to develop fish standards.However, retailer standards are graduallybeing brought in. As with other countries, fishare the last on the list for these standards andthere is no agenda for production of thesestandards in the immediate future. In spite ofthis, this issue does have a rising profile andthere are now industry moves to developthese humane methods and integrate theminto the industry with minimal cost. The mainprinciple that will help this transfer of systemsis the significant product quality benefits thatcan be seen, and in some cases the reductionin production cost. Although my time in the USA proved difficult interms of access to farms and cancelledmeetings, it did result in an invite to present atthe Aquaculture America conference inJanuary 2005. This proved a much morepositive visit and meetings were held withvarious members of the the industry andassociated bodies, and discussions were heldover potential improvements. Thepresentation received a positive reception andpeople were interested in the practicalaspects of implementing new systems and theassociated benefits. I understand from furthercommunication, that some organisations areseriously considering more humane methodsof slaughter and research has now started todevelop viable systems.

Study tour


Mexico (30 October - 6 November)My week in Mexico was spent with a Mexicanfamily in the state of Michoacan. The weekinvolved work with a research institute that isdeveloping new fisheries with Mexicanfarmers helping them back into aquaculture.Processing plants and fish farms were allvisited during this week. Species includedtrout, pez blanco and tiliapia. Over recent years a number of the lakes inMexico have seen their fish stocks graduallydepleted due to years of over-exploitation,poor management and an increased fishingeffort of the lakes with little management and,more recently, pollution affecting the stocks.This also means that the future potential forsignificant growth is minimal. Most (70%) of what has been reported as"aquaculture" in Mexican fisheries statisticsactually comes from inland fisheries of mostlyintroduced species with few native speciesbeing produced.Inland fisheries catches amounted to89,513mt in 2001, with 73% of that beingtilapia. Other important species are rainbowtrout and channel catfish.In Mexico aquaculture only represents a smallcontribution to the national economy (0.8% ofGDP) and the majority of inland fishermendevote most of their time to agriculture, withfishing being only a part-time activity. Thismeans there is relatively little investment inthe industry and methods of low technologyare employed. Mexico's main customer is the United States,59% of the total exports' volume but 85% ofthe total value (as frozen shrimp comprises30% of the exports to that country). Importsinto the country come mainly from the US(34%) and Chile (15%).At the moment there are a number ofconstraints that affect the progression of theindustry. These include social constraints,lack of definition of particular issues likeoverfishing and lack of legal and practical

guidelines to face the problems. Initially, Mexico was included due to itincreasing prominence in the bluefin tunaindustry (10% of world production of bluefin).Mexico is now the third largest producer(Spain and Australia are the other two maincountries). However, despite contact withvarious industry bodies, farm visits could notbe arranged so alternative species andsystems were viewed (tiliapia and trout). Tunais a high-value product and will greatly benefitfrom humane slaughter methods, especiallyfor fish being exported, where improvedproduct quality will have a significant impacton the price of fish. This means there is morescope for implementing systems that maybeinitially more expensive. Mexico was also chosen as it is a developingcountry that exports to a number of countriesincluding the USA. When looking at new slaughter methods it isimportant to assess what the requirementsare and what options are realistic. As acountry with little investment in aquaculture itis pointless introducing systems which areexpensive to run, are technologicallyadvanced or dependent on high maintenanceunless there are significant benefits. Mexicanfarmers realise a very small profit from fishand there is currently no real domestic marketfor high quality products. Without this mainincentive, and very low profile of animalwelfare, the industry is unlikely to have anyincentive to changing systems. Equally, as it isnot a main industry, in relatively poor areasthere is not the finance for new systems. The Mexican leg of the study tour highlighteda range of issues and gave an insight into lowtechnology aquaculture and futurerequirements. One of these could be lowtechnology electric stunners which deal withbatches of fish and may provide benefits suchas quicker harvests. However, this will only bebeneficial if labour is expensive, which is notnecessarily the case.

Study tour


Chile (6 November - 22 November) The first ten days in Chile were spent inPuerto Montt and Chiloe Island. This area isthe main base for many of the aquaculturecompanies in Chile, including many of theinternational companies. The last few dayswere spent in the capital Santiago. During thevisit a number of fish farms and processingplants were visited and meetings with industrygroups and research bodies were held.

Whilst in Chile, salmon and trout were viewedin a wide range of systems.

Chile occupies an important place in worldaquaculture, being amongst the top fourcountries for salmon production. Aquaculturestarted developing in the 1980s, mainly basedon the culture of salmonids and, at a lesserlevel, molluscs, clams and seaweeds. Thereare varying sizes of enterprises which spreadfrom subsistence level to enterprise levelachieving industrial sized production.

During 1998, the aquaculture sector reachedlevels of about 361,4 thousand tones and hashuge potential to expand further. Chileundoubtedly has the possibility to maintain, ifnot improve, their second place as a worldproducer of salmonids.

As a major salmon producer, Chile exports toa wide range of countries in frozen form.Throughout the trip it was apparent at howmuch concern this causes the other countries.With cheap labour and the ability to producelarge numbers, other markets find it verydifficult to compete with the prices of frozensalmon. Equally Chilean farmers are rapidlyimproving their systems to become moreefficient and improve their quality.

One explanation for this is the insurgence ofmulti-national companies into the industry.These companies bring expertise, technologyand finance into the Chilean industry andhave helped improve its systems, making theproduction chain even more efficient andmore lately increasing the quality of the fish

significantly. However, systems are notalways transferable from one country toanother and this expectation can causeinternal problems.

The methods of slaughter employed varygreatly as the technology gradually filters intothe country and industry. Methods observedincluded live chilling, carbon dioxide,anaesthetics and percussive stunning(manual and automatic).

In Chile the industry generally uses specialcompanies for the harvest of fish. These canbe companies that travel to the farm site andkill on a specially designed harvest boat orspecific killing sites. Harvest companiesemploy their own staff and farms only provideone member of staff to monitor the crowdingand removal from water. Specific killing sitesrequire the fish to be transported away fromthe farm. These sites have holding pens forthe fish to be kept in prior to slaughter. Thissystem has the added advantage ofspecifically trained staff doing one job, so itcan be expected they will be competent at thejob. It does, however, mean that the control ofthe harvest procedure is passed from the farmto the harvest company. This potentialproblem has been targeted by some farms byproviding training for the harvest staff.

The methods observed in Chile varied in thefinancial investment and level of technology.This had obvious impacts on the relativewelfare merits of the systems employed.

Over 20 species of fish are used in theaquaculture industry. Of these, only a few arewidely grown on a commercial basis, iesalmon, trout and tilaipia. A much widervariety of species is developing and is still atexperimental stages, with ongoing researchdiscovering breeding cycles, feeding regimesand water quality parameters suitable to farmthese fish in a relatively intensive nature.

This section highlights the most commonlyfarmed species observed during the project.

Salmon Within the salmon family there are a numberof species farmed including:

Atlantic Salmon (Salmo salar)

Alternative names: Bay, Black or Silver

The Atlantic salmon is farmed all over theworld and was observed in Canada and Chile.Harvest size can vary from 3-10kg dependingon the customer requirements and season.

Fish spend the first part of their life in freshwater before being moved to sea water. Fishare grown in cages to the required weight. Forharvest, fish can either be killed on site ortransported to the processing plant alive. Careneeds to be taken to ensure that these fish donot start to mature before harvest. When theydo their shape alters and the use of automaticpercussive stunning becomes less effective.

A variety of harvest methods for these fishwere observed including carbon dioxide,percussive stunning and anaesthetic.

These fish are widely transported, and whendone correctly this will have a relatively smallimpact on their welfare.

Chinook (Oncorhynchus tshawytscha)

Other names: Spring, Pacific, Quinnat or King

The chinnock salmon is originally from thePacific Ocean and is significantly different tothe Atlantic in terms of husbandryrequirements, as it is a lot more flighty.

Chinook salmon react to interaction withhumans by very active movement which coulddamage the fish externally and also increasethe stress hormone production. Althoughsome companies live-haul chinook, it is notcommon practice as they react badly to theincreased handling and reduced stockingdensities experienced.

Chinook are farmed in Canada (west coast),in Chile and in New Zealand. Methods ofharvest observed included automaticpercussive stunning, anaesthetic and carbondioxide stunning.

Coho (Oncorhynchus kisutch)

These are also Pacific fish and are similar tothe chinook in terms of reactions andproduction requirements. These fish aregenerally harvested around 4–5 kg.

They are native to Canada, the USA (westcoast) and Mexico and are caught in Alaska.They have been introduced into Chile and anumber of other countries. During the visitmethods of harvest observed included carbon

Farmed fish species


dioxide. Rainbow trout (Oncorhynchus mykiss)These fish were observed in Mexico, but arealso widely farmed in the USA, Canada, andChile. They are native to Mexico, Canada andthe USA, but have been introduced tonumerous countries including Chile and theUK.The slaughter methods observed includedashyxiation and live chill (larger fish of similarsize to salmon). Other methods discussedincluded death in ice slurry, carbon dioxidestunning, electrical stunning and percussivestunning. In Canada and the USA there is alsoa significant market for live trout. This meansthat many of the fish are transported and heldlive in retail outlets ready for sale.Channel catfish (Ictalurus punctatus)Catfish are farmed in ponds in the south of theUSA and Mexico. They are generally sold infrozen form around the country. However,some producers are close enough to marketsand will live-haul the fish to gain nearly doublethe price of frozen fish. Fish are generally soldfor slaughter at 1.4kg. The catfish is the mostcommonly farmed fish in the USA. They aretransported live to processing plants wherethey are immobilised or stunned with electricbefore being decapitated. White sturgeon (Acipenser Transmontanus)Sturgeon are one of the oldest livingveterbrates with fossil records detailing backmore than 150 million years. Historically, thefish has been used for caviar production butmore recently people are looking into foodproduction. As the fish are very long lived, thefemales can take up to 8 years in farmedconditions (15–20 years in the wild) to reachsexual maturity. The fish are sexed at 3–4years old and the males separated and soldfor meat, whilst the females kept on for eggproduction. These fish can be difficult to kill asthey are capable of surviving on relatively lowlevels of oxygen. They are increasinglyfarmed in Canada and the USA for foodproduction.

Arctic CharrThis is one of the new species and wasobserved in a research station. This fish isvery different to typical salmonids andprovides different challenges to aquaculture.As it is only four or five generations removedfrom the wild, it cannot be guaranteed to haveconsistent production factors like growth ratesand feed conversion ratios. As the charr preferhigher stocking densities they have thepotential to be a very successful aquaculturespecies with further development. Tiliapia (oreochromis niloticus)

As the world’s most widely cultured fish,tiliapia accounts for 20% of the global seafoodharvest. Male fish are preferred due to the fastgrowth potential. Originally hormonal sexreversal was used to produce male-onlygroups, but this is now being replaced bybreeding polices which are just as effective. Hybrid Striped Bass Alternative names: Sunshine or PalmettoThe bass family form a large part ofaquaculture around the world. The first hybridwas formed in the 1960s with a white bass(Morone chrysops) and striped bass (Moronesaxatilis). Depending on the sex of theparents this produces either the sunshinebass (striped male - white female) or palmettobass (striped female - white male). Unlikemost hybrids these fish can breed. Originallyfrom the Atlantic coast of Canada and theUSA, they can now be found along the westcoast and in inland populations. They are alsowidely produced in Europe. These fish aregenerally harvested at an average weight of1kg. They are warm water fish with optimumgrowth occurring at 25-270C. The method ofslaughter for these animals is generally in iceslurry.


Farmed fish species

Withdrawal of foodHistorically food has been withdrawn to savecosts, avoid taint in the final product,manipulate flesh composition, or for foodhygiene reasons. Science has now shownthese problems are not always resolved byfeed withdrawal. In some species, such assalmonids, 72 hours is sufficient for completegut emptying resulting in a safe product withno taint. Food withdrawal purely to savemoney proves uneconomical as it has noimpact on fillet quality and will result in weightloss, especially in warm water species. Foodwithdrawal raises a number of questions. Inthe wild, certain species naturally fast for longperiods and some people believe this isevidence that food withdrawal is not a welfareconcern. However, farmed fish are fed dailyand at regular intervals, a procedure that thefish get accustomed to and it is argued thatthis withdrawal could be detrimental to welfareand may increase aggression. As a result,best practice is to keep withdrawal time to aminimum and never longer than necessary forcomplete gut emptying.

Crowding Crowding is an essential procedure to aid theremoval of fish from water, but it can causeunnecessary suffering when done incorrectly.It must be correctly managed to minimise therisk of adverse impacts on welfare and quality.Unless carefully controlled, crowding canresult in: rapid increase in stocking density decrease in oxygen levels deterioration in overall water quality significant increase in risk of abrasion of

fish from nets and other fish To minimise all these risks, monitoring of thepen by experienced staff must be continuous.Practical observations can help indicateincreasing stress levels. The behaviour of fishshould remain as normal as possible. Whenfish are stressed their movements tend to

become more vigorous; if this happens, netsshould be loosened until the behaviour calmsdown. The nets should be brought in slowly sothat the area is reduced gradually. Thisreduces the chances of scale loss, eyedamage or aggression, as individuals areforced closer to each other. Where possible,the crowd nets should be gathered in such away that the sides are slack rather than tightand rigid. This makes the nets flexible and willreduce the chance of damage. Crowding must always be undertaken at anappropriate rate for the subsequent handlingoperation. Where possible, it should not lastlonger than two hours. If it takes longer, theprocess should be reviewed and the way inwhich the pen is split re-examined. A simplescoring system can be developed byexperienced staff to help train others torecognise both acceptable and unacceptablelevels of activity, so that procedures can beput in place to resolve problems. Clean andwell-maintained nets are essential for humanecrowding, as is monitoring oxygenconcentration. Water quality can deterioraterapidly, if not monitored, as carbon dioxideand waste levels increase and oxygen isdepleted. If the oxygen levels fall below thecritical level for that species, oxygen shouldbe added to alleviate stress. The addition ofoxygen to the crowd has another advantage:it attracts fish towards the diffuser. It isimportant that the correct type of diffuser ischosen to ensure the level is suitablethroughout the entire harvest. Water qualitycan also be maintained by allowing a goodwater exchange.

Pre-harvest treatment


Removal from waterRoutine husbandry practices and someslaughter methods require removal of fishfrom the water. When this happens, it will elicita stress response from the fish as they try toget back into the water. Whilst a brief periodout of water often cannot be avoided, theymust not be left in air for any longer thannecessary, ie 15 seconds for salmon atslaughter. Unless the species can survive outof water, activity levels generally increaseafter this, along with stress levels and chanceof injury due to difficulty in handling. Theremoval rate must coincide with the speed ofthe husbandry procedure so that fish aredelivered appropriately with a minimal timeout of water. The three most common deliverymethods are hand nets, pumps and brailles.The use of anaesthetics can also be usefulduring this process to alleviate stress.

AnaestheticsIn some countries (New Zealand, Australia,Chile and Korea), an anaesthetic agent withthe active ingredient iso-eugenol, is licensedfor use to sedate fish prior to removal from thewater. This anaesthetic (AQUI-S Ltd, NewZealand), which can be used immediatelyprior to slaughter in the licensed countries, isapplied in solution to the water. The fish areintroduced into this treated water, where theyremain for 30 minutes. Following sedationthey are removed from the water andpercussively stunned or introduced intocarbon dioxide saturated water. This type ofharvest is known as 'rested' harvesting.Rested harvests improve flesh qualityparameters such as: improved colour,reduced gaping, and a delay in the onset andseverity of rigor compared to conventionalharvesting methods. This is mainly due to thefish experiencing less exercise and stress.Currently applications are being made forlicenses to use iso-eugenol in both Europeand North America, but until these are granteduse of the product is not permitted outside ofthe licensed countries.

Practical implications:Used correctly prior to removal from water, atthe point of crowding, AQUI-S is a veryhumane method to crowd fish quietly andremove potential injury as the fish areremoved from water. Many companies which are currently incountries without the licence have used analternative to AQUI-S such as clove oil. This isa natural product but the concentration of theactive ingredient can vary greatly socontrolled use can be difficult to achieveunder commercial conditions. Some companies visited had used clove oilbut mentioned problems with taint. Where it was observed, it was added to thetank in addition to carbon dioxide followingremoval from water. This was providingwelfare and product quality improvements butnot to the full potential if used correctly. Theproblem was that this fitted into the systemand was a cheaper way of using it. Theimprovements had been recognised andtherefore there was no immediate decision tofollow the recommended procedures whichwould require alterations to the systems andslight increase in costs.

Welfare implications:Positive:

non-aversive way to reduce movement offish and induce unconsciousness if used atcorrect concentration to minimise thestressors they experience

controlled and repeatable way of inducingunconsciousness. If used correctly, the fishwill remain unconscious whilst bleedingoccurs

Negative: if used at incorrect concentrations it may beaversive

if not left for long enough, fish may besedated rather than anaesthetised



Pumps and pipesA variety of pumps are used for handling fish,so the choice of pump is dependent on eachindividual situation. Whichever pump is used itshould be maintained well to avoid any type ofdamage to the fish and to be powerful enoughto handle the volume.

Pipes connecting the crowd pen to thestunning point should be as short as possible;many well-run systems keep the time fishspend in a pipe below a maximum of twominutes. Any delay can have an adverseeffect and increase stress levels. At the end ofuse, and during any extended breaks, pipesmust be flushed through to ensure they areempty. A sponge ball of suitable size can beused to ensure effective flushing of the pipes.

When using pipes, placing the pipe inlet in ashaded area and in the correct orientation forfish to swim towards it against the side willutilise natural behaviour and will helpminimise stress.

Practical implications:Pumps can add costs to production but theyare an effective way of delivering fish to thestunning point and are suited to the wholerange of slaughter methods. Pumps have tobe maintained to prevent injury to the fish.Long pipes can also cause problemsespecially in warmer countries; if fish are leftin the pipes for too long there is a risk of anegative impact on product quality


fish are not lifted out of water

fish are not exposed to the forces of gravity

less change of abrasion injuries and fishbeing crushed or suffocated fish are delivered at a reliable andcontrolled rate suitable for all methods ofslaughter.

Negative: long pipes in hot countries can expose fishto higher temperatures than normal

long pipes may exhaust the fish if they tryand swim against the current

incorrect set up of pumps may injure fish

BraillingBraille nets are a quick way of moving largenumbers, but this process can seriouslycompromise welfare when fish are fullyconscious. A lining should be used in thebraille to keep water within the nets and toprovide some protection when fish areremoved from the crowd pen; it alsominimises the risk of skin and eye damagecaused by abrasion from the nets. Overfillingbrailles must be avoided at all costs, as thiswill cause undue pressure on the fish andsome may die due to suffocation. The braillemust be well-maintained and regularlychecked for damage. Where linings are notused, the mesh size must be appropriate forthe species/size being brailled; there must beno rough edges on the sides, nor chainswhich may cause flesh, skin or eye damage.The braille net must be moved slowly andlowered to make contact with the unloadingtable before the fish are released, otherwisewelfare and quality will be compromised.

Time spent training the crane driver to loadand unload braille nets correctly is invaluableto minimise welfare concerns and maximisequality.

Practical implications:Brailles are an effective way of moving largenumbers of fish, but their success in notdamaging the fish is dependent on the skill ofthe crane driver. The temptation to overfill,move the nets quickly and unload withouttouching the table must be avoided.




if a lining is used fish are not exposed to thefull force of gravity

Negative: without a lining, fish may be crushed orsuffocated

fish are at risk of damage from the net, thisincludes skin damage and eye damage aswell as bruising

the braille can be overfilled

fish are at risk of injury if the braille isopened above the table and fish allowed todrop

it provides fish in bulk and is therefore notsuitable for many of the humane systems ofslaughter

fish may need to be crowded tighter toallow filling of the braille net

Hand-netsIn many ways, removal of fish by hand-net isvery similar to removal by braille. Hand-netsare unlikely to have a lining, so it is imperativethe mesh of the net is suitable for the species.Again welfare will benefit immensely fromquality staff training, specific to the species.

The use of hand-nets often requires staff to bein the water with the fish, when this happensstaff need to know how to minimise anyadverse effects this will have, such asdecreased water quality, increased activityand possible crushing of fish by operatives.With such procedures staff welfare is alsoimportant as this impacts on fish welfare; tiredstaff or poor working conditions cancompromise the ability to work effectively andtherefore compromise welfare.

Practical implications:The use of hand-nets relies heavily on the skillof the operator. Operators need to be trained,and avoid damaging fish when working in thefish ponds.


small numbers of fish can be lifted out of acage/pond

Negative: there is a risk of damaging the fish aroundthe operator

fish are at an increased risk of damagefrom the net, this includes skin damage andeye damage

fish are at risk of injury if the hand-net is notemptied carefully

it provides is a slow way of removing fishand could lead to extended crowding times



Principles of humane slaughterThe key principle of humane killing is torender the animal immediately insensible, acondition which must then persist until it isdead. With red meat animals and poultry thedefinition of unconsciousness is generallyaccepted as the point when normal rhythmicbreathing stops. Research suggests that thisis also true for fish.

At no point should fish be handled in a waythat causes unnecessary suffering. In recentyears various systems have been developedin an attempt to achieve this. Historically,common methods of slaughter were verybasic, ie a manual blow to the head orremoving the fish from water. These methodsare low cost and were thought to be effectiveand acceptable. However, as aquaculture hasadvanced, new systems have been designedand improved and more are underdevelopment. This has resulted in a range ofoptions for the more commonly culturedspecies, which satisfy the requirement forhumane slaughter to differing degrees.

Within the UK, producers have embraced theidea of fish welfare and have moved forward,developing methods of slaughter that aremore humane, whilst still being able tocompete in the competitive market. Followingthis industry development, many qualityassurance schemes now include therequirement for humane slaughter.

Over the past ten years the industry hasprogressed from traditional methods that havebeen shown by research to compromise thewelfare of fish to modern humane systems.

Around the world, technology is at differentstages of implementation and development.Much of this is dependent on the country andthe people involved in the industry.

All the methods observed and discussedduring the project are listed below.

It is clear from previous experience, andbacked-up by the study tour, that what works

successfully on one farm will not necessarilybe the same for other farms, and likewise forcountries. Therefore each of the methods isdescribed in terms of theory, practicalimplications and the associated welfareadvantages and disadvantages for the fishand the practicalities of fitting such systems.

Changing slaughter systems is a long term,often expensive, project. For these reasonsrecommendations are given at the end toimprove methods that are not regarded ashumane until decisions can be made aboutthe long term systems.

As previously explained, the stress responsein fish is indicative of a compromise in welfareand can potentially damage product qualitywhen it occurs prior to slaughter. It is thereforeessential that slaughter methods reduce thisstress response whenever possible.

New methods take advantage of moderntechnology and some are highlysophisticated, but simple systems are alsoavailable relatively cheaply. When costingsystems it is important to keep in mind thebenefits that humane methods may bring;some companies that have converted to morehumane systems have seen profits exceedinitial investment relatively quickly.

Staff trainingA sound understanding of the methods usedis essential for operators to perform their jobeffectively. Husbandry is an extremelyimportant and skillful job; the benefit oftraining staff to ensure and maintain highstandards of welfare cannot beunderestimated. All staff involved with livefish, including crane drivers moving braillenets and wellboat crews, should beappropriately trained and have theconsequences of poor managementexplained to them.

Killing methods


Percussive stunning

The objective of percussive stunning is toinduce immediate insensibility byadministering a severe blow to the skull of thefish which causes irreversible brain damage.It is essential that the blow is applied withcorrect force, in the correct place to ensure aneffective stun that will kill the fish.

The initial effect, when hit correctly is for thefish to become rigid, lose opercular (gill cover)movement. Its mouth opens, and eye reflexesare lost. This period of rigidity can vary inlength depending on the force of the blow, butalso with age and species.

As stated above, an effective stun isdependent on the blow being administered tothe correct part of the skull. To ensure themaximum impact on the brain, the bestposition is where the brain is closest to thesurface of the head and where the skull is atits thinnest. In most fish this is the regionbehind the nose and above the eyes. Theblow does not have to penetrate the head tobe effective.

When using percussive methods, fish shouldbe presented to the stunning point carefullyand at a rate suitable for the staff carrying outthe stunning. If left out of the water for toolong, fish will start to flip and become moredifficult to handle.

Signs of an effective percussive stun: no opercular (gill cover) movement

no eye movement

bulging of muscle ring near pectoral fin (Atlantic salmon)

PriestThe priest has been an effective method ofstunning fish for many years, but to behumane it relies heavily on the strength, skilland consistency of the slaughter team.

Practical implications:Used correctly, the priest is a humane methodbut it is difficult to expect staff to reliably andaccurately hit large numbers of fish at a raterequired for commercial harvests. As staff tire they will become less accurate.This not only affects the welfare but can causemeat quality issues that will increase theamount of downgraded flesh.

Staff run the risk of developing conditionssuch as repetitive strain injury, which canprevent them from further work and may resultin litigation.


hit correctly, insensibility is causedimmediately, which will persist whilstbleeding occurs

Negative:

immediate insensibility is not alwayscaused due, to: incorrect placement,insufficient power or operator fatigue and orinaccuracy

second or third blows are often needed

the longer a fish is held the more it willstruggle and it will be increasingly difficultto apply an effective stun

manual handling and restraint of fish isrequired whilst fully conscious

fish need to be removed from water.

there is a risk of eye damage and bruisingwhilst conscious

Killing methods


Mechanical systems - manual feed

The 1990s saw the development of automatedsystems, mechanising the stunning operationand potentially making it a more consistentlyhumane procedure. The operator gently graspsthe fish near the middle of the body (not by thetail), guiding it into the opening of the machine toensure the fish is upright. The fish activates thetrigger system, resulting in the piston striking thefish on the head rendering it immediatelyunconscious.

Practical implications: The system is more user friendly and does notrely on human skill or strength. Once theoperator is competent with the machine itbecomes relatively easy to operate, although itmay slow down the stunning rate initially.

Fish are still when they reach the bleed pointmaking it easier for the gills to be cut andproviding for a cleaner environment for theworkers. Less staff may be required at thestunning point, meaning that one member ofstaff can solely operate the crowd pen. There isan initial cost for the machine, which is notgenerally prohibitive, but the system will workmore effectively and humanely with a pipedelivery system as opposed to the braillingmethods.

Not all mature or deformed fish activate thetrigger at the right time and therefore do notreceive an adequate blow to cause immediateunconsciousness and will need restunning. Manual handling is still needed, and should fishbe left out of water for any period of time theywill become more active, this may lead tobruising as they flap but generally makes it

harder for the fish to be guided into the machineand they will need to be restrained, potentiallycausing bruising.This system has greatly reduced the risk andoccurance of repetitive strain injury in staff.Throughput can be increased and less staffused. Welfare implications:Positive:

position and power are far more consistent,ensuring accurate and effective stunning onall fishless chance of ineffective stunningless risk of eye damage or bruising whilstconsciousless manual handling as fish are guidedrather than physically restrained

Negative:fish need to be handled and removed fromwatera small number of mature or deformed fishmay not be effectively stunnedthe system is more suited to delivery by pipesthen brailles

Mechanical percussive systems -automatic feed

This machine is one of the most recentdevelopments in humane killing equipment andfurther improves percussive stunners. These stunners utilise a specially designed tablewhich keeps fish in the water until secondsbefore being stunned.

Killing methods


Once on the table fish are encouraged, using araised surface and water currents, to swim to thefront of the table and jump over into the deliverychannels. The delivery method requires pipes,as brailles would not be effective.At the bottom of each channel is a stunningmachine.These are triggered in the same wayas the manual feed machines. Followingstunning the bottom drops and the fish fallsthrough to the bleed area. Practical implications: The machine can be expensive and timeconsuming to fit: many companies have had toredesign the table more than once, for it to workeffectively. However, once working it has beenproven to increase both welfare and flesh qualityof the fish in commercial situations. Correct design of the delivery table is essentialand is generally unique for each site. Althoughstaff can be relieved from regularly stunning thefish, it is important that they still remain withinthe area to monitor the fish coming through andlook for fish that have not been hit correctly. Fishalso swim to the edge of the table and use theoutside stunners more regularly than the insideones. It can be expected that this can bestressful as they try and free themselves, theywill also be out of water at this point Observations of this machine in operationshowed that the majority of fish, includingmature fish, received an effective stun first time.Manual back-up stunners are required though. Welfare implications:Positive:

the fish’s natural behaviour is utilisedfish are not handledthere is minimal time out of water

Negative:a small percentage of fish go through in thewrong orientation. Being hit upside down willnot produce an effective stun as fish swim to the outside channels therecan be blockages (very small occurrence). some people believe that the fish are more

active and therefore will produce higherlevels of lactic acid but practical use hasshown this not to be the case

General considerationsOperator considerations The design of the stunning table and of thedelivery method to the table/machine is ofutmost importance for both fish welfare and theoperators’ health and safety. Staff should nothave to concentrate on keeping their balance, orbend excessively when using the equipment, asthis can lead to tiredness and inaccuratestunning, which in turn can lead to acompromise in welfare and product quality.Failure to stunIf a fish is not properly stunned it must be re-stunned immediately. As described above,manual percussive stunning of fish does notalways cause insensibility. Practical observationof this method showed, that whilst an operatorcan be very effective when just starting the job itis not long (30 minutes) before multiple blowsare needed to render the fish insensible. This not only causes welfare issues but mayalso cause poor flesh quality through bruising,eye damage and increased production of lacticacid.

Automated mechanical stunning systems aremuch less likely to ineffectively stun when usedcorrectly and maintained correctly. It is essentialthat all fish are monitored for stunning efficacyand corrective action taken if a problem arises.If the machine is at fault it should be removedfrom the harvest immediately until fixed. If it is just individual fish, ie mature fish, thenconsideration should be given as to whether ornot to use the machine or a priest. If there isdoubt that any fish has not been stunnedeffectively, the priest should be used to repeatthe stun.


Killing methods

Carbon dioxide narcosis

Loss of consciousness in fish immersed incarbon dioxide saturated water (pH level 4.5),which is highly aversive, can take 7–8 minutes.Fish will show head shaking and vigorous tailshaking for up to two minutes after immersion inthe solution. Movement then subsides and thefish become still after five minutes. This is due tonarcosis (loss of control of movement) andexhaustion as opposed to insensibility. Unlessfish are kept in a high concentration solution for7–8 minutes, recovery will begin soon afterremoval from the solution, ie on the table or inthe bin and the fish will be conscious whilstbeing bled.

Practical implications:To ensure that all fish are rendered unconsciousthere needs to be a significant exposure timeand the correct concentration. Exposure to thecarbon dioxide causes significant and vigorousmovement; this makes the area in which staffare working more difficult but will also haverepercussions on the quality of the fish and isclosely associated with a very quick time to rigor(less than 2 hours in one plant).


if they have been exposed for the correctamount of time, at the right concentration, fishmay be unconscious as the gills are cut

Negatives:loss of consciousness is not immediate

carbon dioxide is aversive to fish and will elicitthe stress response

it is very difficult to control in commercialconditions and ensure sufficient exposure

there is a high risk of fish not beingunconscious when gills are cut

concentration of the gas will vary and may notremain at the level sufficient to causeunconsciousness

Live chillingLive chilling is used around the world for largerfish which are going to be bled. Fish are addedto a chill tank which has the water temperatureset at around 1OC. This method immobilises fishand reduces the carcass temperature to allowquicker processing. It is not a method ofstunning fish and will not induceunconsciousness. When fish enter the tank theymay show violent movement and escapebehaviour. This movement gradually subsidesas they become exhausted and or immobile.After about 30–40 minutes they are removedfrom the water and their gills are cut whilst stillfully conscious.

Where chilling is used the rate of chilling shouldnot exceed a drop of 1.5OC at any time. It isessential that the water quality is maintainedand that oxygen, carbon dioxide and ammonialevels are measured and controlled, bychanging the water throughout the day. Somesystems also add carbon dioxide into the systemto help speed the process. Carbon dioxide hasits own effects on fish which have beendiscussed in detail above.

Practical implications:Live chilling machines are bulky and relativelyslow. Fish are dewatered prior to entering thetank, and either a pump or a braille method ofdelivery works for these systems.

Fish are chilled and the core body temperatureis brought down relatively quickly, allowing fishto be processed quicker and potentially have alonger shelf life. However, the reaction seen byfish as they enter the system is highlysuggestive that the system is aversive.

Killing methods


As an alternative, systems were observed whichused chilling for 30 minutes after killing. This hasnone of the associated welfare disadvantages oflive chilling and the factory commented that thefish were still leaving the factory below therecommended temperature set by governmentfor food safety reasons. The fact that the fishhad been bled and therefore little circulatorysystem seemed to have no effect on the time ofcooling, but it significantly improved the welfare. Some systems include carbon dioxide in them tostun the fish. This is an aversive gas for the fishbut due to immobilisation they cannot react tothis. The advantage of carbon dioxide is that,done correctly, it will cause unconsciousnesseventually so fish will not be alive when the gillsare cut. However, unconsciousness by carbondioxide is difficult to induce under commercialconditions.

If fish are put into live chill tanks that actuallyhave the same temperature as the water thatthe fish have been farmed in, they willacclimatised to this temperature and no matterhow long they are in the chill tank there is noimmobilisation.

Welfare implications: Whilst many fish will spend a significantproportion of time at low temperatures, theyreach these by slow acclimatisation, around fourdays, and will show a violent escape behaviourwhen placed in water with a 10oC difference.

Positive:

this is not a quick way of inducingconsciousness and there are no positiveimplications for welfare

Negative:

live chilling does not cause unconsciousness

sudden exposure to chilled water will causeaversive reactions in fish

Death in ice slurry

Death in ice slurry is one of the most commonmethods of slaughter around the world and iswidely implemented in the trout industry in NorthAmerica. Fish are passed over a dewaterer andinto a slurry mix of ice and water. They are thenleft in this mix until they die through lack ofoxygen. As the fish’s metabolic rate slows downin colder temperatures so does the oxygendemand of the fish. This means that the time todeath whilst in ice slurry can be considerablylonger than asphyxiation. In other warm waterspecies, fish can also suffer temperature shockwhich may shorten the time to loss ofconsciousness.

Research into trout has shown that the time forloss of consciousness can vary from twominutes (in air) to nine when put in ice slurry.

Practical implications: This is a low-tech method of slaughter andrelatively cheap. It can reduce the core bodytemperature helping the processing procedures.However, some scientific work has shown thatthere is an increased production of lactic acid asthe fish show vigorous movements on initialcontact with the water.

When fish are placed in ice slurry, it is difficult touse normal behaviour indicators (such asescape behaviour and vigorous swimming) asindicators of welfare, as the ice can have animmobilising effect on the fish. In thesecircumstances fish will be relatively still, apartfrom sporadic flips.

Killing methods


Welfare implications:Positive:There are no benefits to welfare for this method.

Negative: the delay in unconsciousness means thismethod cannot be described as humane

in certain circumstances there is a chancethat fish are immobile not fully unconsciouswhen they reach the processing plant

Death in air This method involves removing fish from thewater, either by hand-nets or pumps and addingto an empty container. When out of water thegills collapse and are no longer capable of gasexchange. This means that the fish die throughlack of oxygen. This is not a method that causesimmediate unconsciousness and is notclassified as humane.

When fish enter the container there is a severereaction seen in the fish, the stress response.The fish show vigorous movements as they tryand return to water.

Practical implications:This is a very low tech method and does notrequire and any set up costs, staff training ormaintenance. The vigorous movements seen bythe fish last for a long time and can be expectedto deplete the energy reserves of the fish maylower quality. Even though the movement isextended (over 15 minutes duringobservations), research has shown thatconsciousness is lost before this time.

Welfare implications:Positive:There are no positive in terms of welfare.

Negative:fish are taken from their natural environmentand have no access to water which isexpected to be inhumane.

they will remain conscious for a long period oftime

Gill cut without pre-stunning This method involves removing fish from waterand then cutting the gills without any pre-stunning.

On removal from water the fish show escapebehaviour and flip their tails. Once the cut intothe gills is made, these reactions aredramatically increased and vigorous headshakes and tail flaps are seen for at least 30seconds. This movement slowly subsides andafter several minutes most fish stop moving.

Practical implications: The method is extremely low-tech, but does relyon a very well trained staff. If gill arches are notcut effectively then the blood loss may berestricted. This will have a negative impact onwelfare and flesh quality. This could also becompounded if the fish is handled badly beforeslaughter. Increased activity causes a build upof lactic acid which will lead to early rigor.Should this rigor start before all blood is drainedit will remain in the carcass, increasing thechance of spoilage and reducing the processingoptions.

As the fish have not been stunned, they willreact to the handling and removal from watermaking it more difficult for the staff to handle thefish. This increases the difficulty of making agood cut and the chances of the operatorscutting themselves.

Welfare implications: Positive:There are no positive in terms of welfare.

Negative:fish will have to be handled and restrainedwhilst the gills are cut and are fully conscious

an ineffective cut will not allow fast andprofuse bleeding

there is significant activity exhibited by thefish

as the gills are cut, this movement increasesfurther

Killing methods


Electrical StunningElectrical stunning was not observed during thevisit but was discussed on a number ofoccasions in the USA and Mexico. It is also ahuman method implemented in the UK. The general principle of electrical stunning is topass sufficient current through the brain tocause an epileptic-like fit. This results inimmediate unconsciousness and insensibility topain. If the current flows for long enough the fishwill die of anoxia before the brain is able torecover sensibility. The electric current also causes spasms in thefish muscle which can, under somecircumstances, result in haemorrhages andother carcass damage. Stunning conditionstherefore have to be carefully designed toensure that the process causes neither pain, norcarcass damage and that recovery is notpossible. These conditions are known to varywidely between different species of fish.The electric current in a tank of water can passaround the fish as well as through them,therefore it is most useful to define the electricfield which is required in the water rather thanthe electric current. The effect of the electricity isrelated to the frequency. Frequencies close to50 Hz have a greater effect on both the fishbrain and muscle than higher frequencies.However, in trout and salmon a frequency of50Hz is likely to cause carcass damage. Byselecting a higher frequency at a slightly higherelectric field strength, immediate insensibilitymay be achieved without causinghaemorrhaging or other carcass downgrading. Stunning with electricity is known aselectronarcosis, and killing with electricity isknown as electrocution. Electronarcosis is afully reversible procedure, immediatelydisrupting normal brain function for a short periodonly. Electrocution leads to complete dysfunctionof the brain which prevents the breathing reflexworking. Electronarcosis by itself is not suitablefor fish that are not bled immediately afterstunning. This is because they would recoverfrom the stun before further procedures could bestarted and they would therefore be fully

conscious during processing.Factors such as species, size, stress levels,temperature, water conductivity and the numberof fish in the stun tank may affect the duration ofinsensibility resulting from a stun. Signs of an effective electrical stun

Eye movement stopsSmall muscular twitchesNo opercular movementFish turns upside down

If an electrical field of insufficient voltage,frequency and duration is applied to fish they willnot be stunned, but they may becomeparalysed. Under these circumstances the fishcannot show typical pain responses or escapebehaviour. Alternatively, exposure to thecorrect current but not for long enough to causepermanent insensibility will result in fish startingto recover.

Practical implications:When using electrical systems it is importantthat the operator can monitor the machine at alltimes. It is also important that operators haveunrestricted access to the safety stop controls.Any person stunning and killing fish must knowthe:

voltage required for effective stunningcorrect duration of stun signs of an effective stun/killsigns of an ineffective stun/kill


animals are rendered immediately insensiblefish can be killed in groups or continuously fish do not need to be physically handledfollowing electrocution, there is no chance oflive fish entering the processing plant

Negatives:if the parameters are not set correctly fishmay receive an electric shock whilstconsciousif only stunned they will recoverconsciousness unless bled effectively

Killing methods


The following pages take into account the aboveimplications and give recommendations for eachmethod observed. Although there arerecommendations for methods described asinhumane, it is stressed that these methodsshould be phased out as soon as possible infavour of more humane methods.

When looking at new systems it should becosted appropriately, in terms of qualityimprovements and cost reductions (water costs,labour costs, time etc.), not just in initialinvestment. Methods should always beimplemented in consultation with staff. Theknowledge of staff using the equipment shouldnever be underestimated, but managementmust also take into account possbile negativityfor new ideas due to resistance to changeespecially if there is concern about loss of jobs. Methods that render the fish immediatelyunconscious are stongly recommended.Throughout the study tour it has beenrepeatedly shown that humane handling andkilling of fish is possible, under most scenarios,without compromising the speed or profitabilityof the system, indeed it can improve both onceset up and running effectively.Humane methods also limit the time out of waterfor fish, or even completely remove the need forfish to be taken out of water. In addition theyalso minimise the handling of the fish and therequirement of individual handling by people. At this point in time the two most humanesystems are automated percussive stunningand electrical stunning (and killing). Thesesystems fit the above criteria and as seen on anumber of visits are cost effective to implement.Talks with companies who have implementedthese humane systems have also revealed:

extended rigor times, allowing, processingpre-rigorimproved flesh quality decreased amounts of skin and eyedamage decreased costs of harvest

Humane methods Priest:Stunning using a priest should be kept to theemergency killing of fish on an individual basis.Where it is used for commercial harvest thefollowing list can help improve the welfare andreduce the risk of flesh damage. These include:

increase number of staff to cope with thenumber of fishregular rotation of staff to prevent fatigueand risk of injurya delivery system which provides the fishat a suitable rate to allow for effectivestunning

Where manual stunning is employed, it isessential for both fish and operator welfare thatthe operators are given regular breaks and areallowed to work at a reasonable rate. Otherwiseaccuracy and effectiveness will be compromisedleading to adverse fish welfare.Mechanical percussive stunner - manual feed: Stunning using automatic equipment is ahumane way of killing animals effectively. Whereit is used, the following list will help the systemrun humanely, effectively, improve the welfareand reduce the risk of flesh damage. Theseinclude:

the system is used where fish are gradedregularly so that the likelihood of maturefish is minimised the delivery method is set at a rate suitableto the stunning rate. Fish must never beout of the water for longer than 10 secondsmachines are regularly rotated andmaintained so that they are working atmaximum efficacy at all times back-up stunners (priests) must beavailable at the stunning pointstaff are trained in the machines’ use andalso the back up methodstaff are rotated regularly to maintainconcentration. Staff are trained torecognise both effective and ineffectivestuns

Recommendations


Mechanical percussive stunner - automaticfeed: Like the manual feed stunner, this is a veryeffective way of stuning large numbers of fish.Although only designed for larger fish now, workis progressing fast for smaller fish (under 1kg).Where it is used, the following list will help thesystem run humanely and effectively:

time is taken, and the manufacturers’guidelines and advice are followed, whensetting up this system

when a bank of machines is fitted, theyshould be rotated so that one machinewithin the block is not overused

deformed fish are monitored and stunnedmanually if required

staff should be trained to recognise andeffective and ineffective stun

Electrical stunning This is a humane method if the fish areimmediately stunned and not immobilised. Thestunning machine should always be set up totake amount of the fish passing though it and thewater conductivity amongst other things, whichare detailed by the manufacturer.

Fish should not be immobilsed by the machinewithout being stunned. Whilst the electricalcurrent is switched on it is difficult to tell thedifference between a fish that is stunned orimmobiliised. However, when the current isturned off, a stunned fish will remain stunned fora period of time afterwards. Fish that areimmoblised will start to move immediately.

Less humane methodsDeath in ice slurry This is not recommended as it does not induceimmediate unconsciousness, especially in coldwater fish. It is acknowledged that this is arelatively cheap and low tech method but shouldbe replaced as soon as possible. Where it isused ice slurry will allow fish to be completelysubmerged in the ice quickly, which canexpected to cool fish quicker and help reducethe time till loss of consciousness.

Live chillingLive chilling does not cause unconsciousness infish, it immobilises them therefore they do notreact to handling or gill cutting.

Where it is used:

fish should be chilled at a slow rate (1.50Chas been set by standards written in theUK)

oxygen levels within the tank should bemonitored and kept above 6mg/l

it should occur after death or at least whilstthe fish is unconscious

it should be followed by a method ofstunning before the gills are cut

Gill cutThis method should not be used without priorstunning of some kind. When it is used:

every cut should ensure that all four gillarches are severed

fish should not be removed from water forany significant period of time, practicalobservations show that fish tend to startmoving after about 10 seconds

the delivery method should be suitable forthe rate of bleeding.

Carbon dioxide stunningWell-run systems must use high concentrationsof carbon dioxide to induce unconsciouness asquickly as possible and hold fish for a sufficientperiod to cause permenant insensibility. Whereit is used, the system must ensure that:

a pH level of 5.5 is maintained

fish are held in this concentration for aperiod of at least 10 minutes

the gas concentration is measured andreplenished as required

It is essential that staff are capapble ofmonitoring the gas tanks and can alter thecarbon dioxide setting as required.

Recommendations


As the amount of technology available to theindustry is increasing, so is the understanding ofhow improving slaughter (including crowdingpractices, transport, de-watering and slaughtermethods) can have an overall impact on the finalproduct quality. These improvements will helpthe industry to produce a more consistent andcompetitive product.

In the UK the industry has taken on fish welfarein a very positive manner and has embracedchange over the past few years. This is partlybecause they have led the changes, unlike otherfood producing industries which were forced tochange following controversial images beingportrayed in the media such as animal welfareproblems or food safety issues.

Although there are laws in place to protectfarmed food animals, these are rarely enforcedon the aquaculture industry and retailerstandards are only just including requirementsfor humane slaughter. By taking the lead, theindustry is now in a secure position of being ableto comply with standards and regulations asthey are applied. This is an example that shouldbe followed around the world and had just beeninitiated in a couple of the countries visited.

Unfortunately this kind of progress will not followin some countries due to the lack of individualcompanies willing or able to invest and moveforward, and parts of the industry not wanting tochange due to historical or cultural reasons.Progress can also be limited where smallchanges lead to some quality improvements,and companies don’t want to invest further eventhough the system is not reaching its fullpotential.

It was mentioned in the introduction thatattitudes vary from society to society and areforever changing. This is very true in theaquaculture industry, but as many companiessee the benefits of humane treatment of animalsit surely must only be a matter of time beforeothers realise they can no longer be left behindas the progressive companies become moreefficient and effective in their role.

The large variability of species, and thecircumstances in which fish are farmed, makesprescribing specific welfare impossible inpractical terms. However, the aim of welfareassessment will always be the same – toprovide a suitable environment for the fish toflourish in and to cater for their needs.

How individual companies reach this aim will bedependent on their particular circumstances; it ishoped that this review has highlighted that,whilst there are no definitive answers, there is awhole range of commercially viable optionswhich can improve the welfare of fish atslaughter.

The information gained from this trip is nowbeing used to develop best practice guidelinesfor fish slaughter, which have been requested byBritish retailers. These will be written inconjunction with the industry to complementother assurance scheme standards and help theindustry further improve with specificrequirements for the slaughter and transport offish.

These guidelines will help retailers maintain thesame standards for slaughter when they sourcefish from abroad. This will ensure that the Britishconsumer can be confident when buying fishfrom supermarkets, that they are buying a highquality product that has been produced to highstandards, regardless of the country of origin.

The Future


Over a year ago I started this project with highhopes and aspirations of developing a morepractical and commercial understanding of theaquaculture industry, especially at the point ofslaughter. The original objectives of the tour were toinvestigate the attitudes of industry, governmentand research bodies towards farmed fishwelfare and to discover international practicesfor slaughter.Over 50 visits and 25,000 miles later, theexperience and knowledge I have gained fromthis entire project is immense and I believe Ihave fulfilled the objectives to the best of myability under the circumstances. Not only have I improved my knowledge andunderstanding of the industry, I have developeda wide range of contacts across the world andhelped bring the subject of fish welfare to theattention of many. Some of these people werevery interested to hear about developments,some were not so keen.The help I received throughout the trip was veryhumbling and whilst I have learnt just how longtwo months is by yourself, I have also found newconfidence both personally and professionally. This comes not only from a great sense ofachievement, but also because I now have farmore first hand experience. I acknowledge thatthis is still limited and it is unfortunate that Icould not get to see as many killing operationsas first planned. However, I believe I have seenversions of most methods now employed inaquaculture. Discussions of these methods withthe staff working with them has also helpedprovide a much more realistic view of thesystems. Speaking with all levels of the industries acrossthese four countries has provided an in-depthknowledge of the future plans for aquacultureand where fish welfare at slaughter fits in aroundthe world. The position of fish welfare varies greatly, notonly between the different countries but alsowithin them.

One common denominator is the fact thatcommercial benefits will bring about change andit is becoming increasingly accepted thathumane treatment of fish will bring about someof these commercial benefits. No amount ofprocessing or packaging will improve a productthat is already in poor condition anddeteriorating, but a prime product will last longer,despite processing and packaging.

So far there has already been a number ofpositive outcomes from this project.

Firstly, through contacts developed on this trip, Itook part in the first animal welfare session heldat the annual conference of the USA’s NationalAquaculture Association Conference in NewOrleans, describing the different methods ofslaughter around the world and theirimplications.

Secondly, production of in-depth guidance notesof the humane killing of salmon and trout hasnow been completed and will shortly bereleased to the industry.

I also have written various articles for industrymagazines and have been asked to contributeto a forthcoming compendium on aquaculture.The information and experience gainedthroughout this trip has also led to thesubmission of two papers which have beenaccepted by another major conference inCanada.

In addition to this, fish welfare at slaughter nowhas a rising profile within many companies andacross the whole industry.

Without the Churchill Fellowship, this projectwould have not been possible and none of thesepublications or presentations would have beengiven to such a broad range of industryrepresentatives.

Conclusions


ADVANCING AQUACULTURE - Oregon State University · Advancing Aquaculture: Fish Welfare at Slaughter...

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