DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

Drowning or Waving? Understanding the Difference, and Coping with Changes in Fisheries

Rik Buckworth, Fisheries Research

www.nt.gov.au/dpifm

Come Rain, Come Shine: Sustainable Development and the Challenges of the 21st C

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

Overview

• Fisheries and Fisheries Research – who we are, what we do

• Drivers of Change - Change is the real issue

• Examples of what we CAN do about it

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

We Are Here Because Fishing Feeds PEOPLE

• Production of food, food security

• Economic value – jobs

• “Nourishment for the soul” – recreational and non-catch values

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

Fisheries Research Provides Information for Management of Fisheries

Fisheries ManagementFisheries Research

Society Government

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

Things WILL Change . . . Drivers

• Climate, other environmental drivers– Warming oceans, sea level change, circulation change,

acidification, changes to river flows, nutrient loadings• Socio-economics – local

– Prosperity – “clean and green”, land use, Australians are moving north!

– Population growth, especially coastal indigenous communities• Socio-economics– global

– Prosperity in China and India – “clean and green”– Fuels? Carbon emission constraints

• Technological – people will get better at catching fish• Catastrophe – a wild card

– Avian flu (what would people do without chook?!), Pilchard die off• Everything interacts!

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

Technological Change is not Always This Obvious

What we aspired to in the 1980s!

Standard barra boat now!

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

Global Ecological Limits to Fishing

• Fisheries already take most of the potential harvest from productive coastal waters

• Overfishing in some areas puts pressure on the rest of the world - thus illegal foreign fishing in N Australia waters

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

Change will happen . . .What to do?

• What are likely changes and potential responses - not all change will be predictable

• Enhance ability to detect change – the biggest problem in fisheries science

• Adaptively manage risks – develop resilient systems

• Northern Australia is in a unique position to do it well!

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

Detecting changes in fished populations

• Changes in abundance – all measures have cost/ benefit tradeoffs:– Surveys (trawl, gillnet, aerial) - $$$– Tagging to estimate abundance - $$ – Changes in age structure - $$– Changes in species composition (logs and

observer) -$– Catch rates - CHEAP – so it is the ‘standard’ way

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

Catch rate changes in shark and grey mackerel

• Are there more sharks and mackerel? Changing target species? Improved technology?

• All of the above!

0

100

200

300

400

500

600

700

800

900

1000

1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005

Year

CP

UE

(kg

/day

)

CPUE shark

CPUE blacktip

CPUE-grey mackerel

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

A Simple Harvest Rule for Guiding a Fishery

Catch the optimum proportion of the fish stock*

Experience shows that this approach is resilient

How . . . ?

Tagging is the most direct way

*Optimum Catch = Optimum Harvest Rate X Abundance

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

Tagging is a good way to measure harvest rates in sharks . . .

• They are tough animals, suitable tags are durable and visible• Small cooperative industry -1540 tagged in current project• … but tricky to handle

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

Three Challenges in Using Tagging to Measure Harvest Rates

• Tagging can change behaviour, expose fish to mortality – not all fish are as robust as sharks

• Tags simply fall out • People do not report tags (what %?)

• Expensive experimentation can overcome these problems ??

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

What about fish that are not as tough when handled? There has to be another way!!

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

What we are Doing with Spanish Mackerel . . .

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

A device for collecting tissue was needed . . .

. . . so we invented one!

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

Genetag process

“Tagging”

“Recapture” Screen fins

DNA f/print

Matches

Get tissue

Harvest rates

DNA f/print

mixing

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

Genetag overcomes several problems

• no tag loss or mortality – tagging is to collect tissue in situ, identify individual fish from msDNA ()

• non-reporting not such a problem - screen the commercial catch for matches to Genetagged fish

• Harvest rate - calculated from proportion ‘recaptured’ and screening fraction

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

Issues - Gene tag monitoring feasibility needs lots of work

• Distribution, collection, storage, databasing of samples• Genetics - Set of DNA markers

– Efficient approach to screening (must do 1000s)– It’s not as easy as CSI!

• Database programming and analysis– dealing with large amounts of data means huge number of comparisons

• Turning results into management responses: A set of monitoring rules and control responses

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

Where are we now?

• Mass data analysis - results in a few months!

• Several confirmed Genetag recaptures

• PROOF OF CONCEPT

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

Cautions

The Genetag approach is proven - making it a fishery wide monitoring method will still be a challenge

• Cooperation of the fishers really helps

• IT HAS TO BE COST EFFECTIVE!

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

Conclusions

• Things will change – probably more radically than they have in the past –with MANY interacting drivers

• The first problem is detecting change, so that consequences can be managed

• The second problem is managing – developing responses to anticipated change, new systems to detect changes, and managing for risk

• We have the tools! And . . .

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

We work bloody hard! WE can do better than . . .

• Any questions?

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

Managing Risk in our Shark Fishery

• Additional considerations –– Illegal foreign fishing, rare unproductive species

• Trigger management actions in response to – – Changes in catch rates (e.g. reduced effort when more larger

species)

– Changes in species composition of the catch (might indicate ecological interactions)

– The biggest danger is in delaying response

• Find a better way . . .

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

Harvest Strategy Management as a Framework for Managing Risk

• An agreed system in which management is more risk averse as uncertainty in status of a fishery increases

• High tier fisheries depend critically on the ability to detect and respond to changes in fish stock status. They have good information available

• Lower tier fisheries rely on risk analysis and risk containment approaches

• Fisheries are not allowed to expand unless there is prior proof of potential – i.e. cannot catch more fish unless there is a real understanding that it would be sustainable.

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

Harvest strategy - Advantages

• Forces exploration of uncertainty and development of a risk averse set of response rules that are agreed BEFORE there are problems

• Thus problems are acted on in an agreed way, not put off

• There is a clear direction for information gathering and experimentation – Reducing uncertainty and risk

• There is a clear basis for cost-benefit analysis for decisions about whether such work would be of benefit.

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

Opportunity: Combined genetic - conventional tagging

• Control - but much more than an experimental control

• Combo-tagged fish could give information on post-release survival and tag shedding – as well as add information on fishing and movement rates

• Recreational tagging could contribute real value in this way >1000 fish in the Darwin area have been combo-tagged!

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

What Fisheries Scientists?

• Insert pictures of Jenny Ovenden and CO.