The Marine Institute Bass Paper

8/14/2019 The Marine Institute Bass Paper

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The Marine Institute, Fisheries Science Services

2009 Scientific Advice on Sea Bass(Draft Version 1)

This document summarises new scientific knowledge on sea bass from the waters around the UK and Ireland. It specifically addresses the issue of stock assessment units and the inshore - offshore movements of sea bass in the Celtic Sea area. The biological characteristics of the species that make them vulnerable to overexploitation are discussed.Data on the status of the stock in Irish coastal waters are poor but angling records indicate that the stock may be depleted. Sea Bass in UK inshore and UK-French offshore fisheries are considered exploited sustainably. The current legislation for Irish waters that restricts sea anglers to 2 specimens per 24 hours should continue. Furthermore, all fishing vessels operating within the 12 mile limit of Sub Area VII should not be allowed to catch sea bass until stock status is further investigated. Irish vessels should be allowed to fish sea bass stocks in other areas of Sub Area VII, where the stocks are sustainably exploited. ICES should be asked to review data on sea bass and propose management measures for the sustainable exploitation of the resource.

INTRODUCTIONSea bass are not managed by the EU under the Common FisheriesPolicy. Furthermore, they do not fit into the standard ICES frameworkfor assessment and advice for a variety of reasons. In the UK, thefisheries are mostly inshore, operated from commercial/semicommercial small boats that are not obliged to provide trip or areabased information. A substantial recreational fishery contributessignificantly to sea bass mortality. Survey information is limited toestuarine recruit surveys in UK and Ireland. In Ireland the fishery isangler dominated. In the UK, there is an ongoing debate as towhether sea bass should be managed as a sport fishery as oppose toa commercial fishery. In Ireland, there are restrictions on anglers and

Irish vessels are not allowed to land sea bass. French and UKvessels fishing in the same area are allowed to land sea bass and thisis a source of intense frustration in the Irish fishing industry (Kupschus,2008).

STOCK UNITSStock units were reviewed by Pawson et al. (2007a) based on theresults of tagging work (see Figure 1). Four management units areproposed; two channel stocks (Divisions VIId and Division VIIe) whilethe sea bass populations in English and Welsh waters in ICES

Divisions VIIa, f, and g and the northern part of Division VIIe could be


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regarded as a single management unit. The bass population aroundIreland can be regarded as a discrete stock for management purposes.Tagging studies have shown that sea bass in the waters aroundIreland do not intermix with British and French fish (see Figure 2).

EXPLOITATIONA study of the sea bass fishery in England and Wales (using data from1985 to 2004) has suggested that bass stocks in UK coastal andoffshore waters are being exploited sustainably. Fishing is at amoderate level and the exploitation pattern gives a near maximumyield per recruit. There has been an increase in exploitable biomasssince the early 1990s (Pawson, 2007b). The status of stocks in Irishwaters is not known. Angling returns from Irish inshore waters showthe stock to be depleted when compared to angling catches in the1960s and 1970s ( Figure 3).

AGESea bass are around the UK and Ireland is long lived and can reach anage of 30 years. In the UK sea bass up to 80 to 85cm are regularlyrecorded from the commercial catch with the record standing at 95cm.Sea bass are slow to mature (age 5 as compared to age 3 in cod).These biological characteristics make sea bass vulnerable tooverfishing

SPAWNINGSea bass undergo offshore-inshore movements during their life cycle.Sea bass begin to spawn in early February offshore in the westernEnglish Channel and the Celtic Sea. They spawn in mid water andtheir eggs are found throughout the water column. As a consequencetheir spawning areas are not as well defined as those of bottomspawners (e.g. herring) which deposit their eggs directly on the bottom.The main spawning area in the Celtic Sea areas is off the northCornwall coast. Sea bass can continue to spawn until late June. Seabass larvae move inshore and at age 2-3 months they migrate into

juvenile nursery areas in estuaries, harbours, backwaters, creeks andshallow bays. For the first 2-3 years of their life , juvenile basscontinue to migrate to deeper water each autumn and return inshorethe following spring. When sea bass are 4-5 their movements becomeincreasingly wide ranging between inshore and offshore areas

CATCHES The long held belief that Irish sea bass are harvested by otherEuropean countries is not proven. Irish sea bass would appear toremain close in to the shore, behaviour suggested from limited

landings data and from the returns of tagging experiments.Furthermore, there is insufficient interchange with other sea bass units


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to replenish Irish sea bass when they are depleted. For the past 30years, sea bass have been an angling rather than a commercialspecies. There are no landings statistics for sea bass but anglingcatch data show that the sea bass stock declined dramatically in theearly 1970s and has not recovered since. There is evidence that sea

bass in Irish waters do not exhibit the same strong recruitments asrecorded closer to continental Europe and the species abundanceremains depressed.

Figure 1: Release positions for sea bass tagged between 2000-2005.ICES divisions are also shown. (Source Pawson et al. 2007a)

SCIENTIFIC ADVICEThe sea bass stock appears depleted in Irish waters and shouldbe allowed to rebuild. The legislation in place for sea anglersshould continue and should be enforced. Sea bass should not beallowed to be caught by commercial fishing operations within theIrish 12 mile limit in Sub Area VII (i.e. applied to all EU vessels).Irish vessels should be allowed to catch Sea Bass in other partsof Sub Area VII where the stock is considered sustainablyexploited. This must be accompanied by a industry self samplingprogramme to collect data on sea bass. The Irish Governmentshould request ICES to examine the latest information on thestatus of sea bass stocks in ICES Sub Area IV and VII andpropose management measures for the sustainable exploitation ofthe stocks from an angling and a commercial fishing perspective.


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Figure 2: Main population movements and proposed stock assessment unitsfor sea bass in ICES Sub Area VII (Source Pawson et al 2007a). Note sea

bass in Irish waters are considered a separate stock.

Figure 3: Catch of Sea Bass per angler day recorded by the Cork sea anglingclub1963 to 2006 (Source: Marine Institute Stock Book 2006).


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Source of Information

Anon. (2007) The Stock Book. Marine Institute 372-374.

Kupschus, S. (2008) Bass what does the assessment tell us, what it doesnt tellus and what we can learn about management. ICES Annual Science Conference2008. Theme Session O: 01.

Pawson, M.G., Pickett,G.D., Leballeur,J., Brown, M. and Fitsch,M. (2007a)Migration, fishery interactions and management units of sea bass in northwestEurope. ICES Journal of Marine Science. 64, (2), 332-345.

Pawson, M.G., Kupschus, S., and Pickett, G.D. (2007b) the status of sea bass(Dicentrarchus labrax) stocks around England and Wales, derived using a separablecatch at age model and implications for fisheries management. ICES Journal ofMarine Science 64, ; 346-356.

Pickett, G.D. and Pawson, M.D. (1994). Sea Bass. Biology, exploitation andconservation. Chapman & Hall.

ENDS

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