Advice October 2012

Transcription

1 Advice October 2012 ECOREGION STOCK Widely distributed and migratory stocks Portuguese dogfish (Centroscymnus coelolepis) in the Northeast Atlantic Advice for 2013 and 2014 ICES advises on the basis of the precautionary approach that there should be no catches of Portuguese dogfish. Stock status MSY (F MSY ) Precautionary approach (F pa,f lim ) MSY (B trigger ) Precautionary approach (B pa,b lim ) Qualitative evaluation F (Fishing Mortality) SSB (Spawning-Stock Biomass) Below any candidate reference point Combined landings Combined relative abundance estimate Figure Portuguese dogfish in the Northeast Atlantic. Left: combined landings of Portuguese dogfish and leafscale gulper shark (thousand t). Right: Relative abundance estimate ( ) based on catch per unit effort for all vessels all areas (black circle = cpue where siki sharks (combined Portuguese dogfish, leafscale gulper shark) catch share >10%; cross = catch share >5%; white square = all vessels with catches; black triangle = all deep-water fishing vessels). Trends in relative abundance estimates show that Portuguese dogfish abundance has declined to levels below any candidate reference point. Landings have declined in response to reduced abundance and restrictive management measures (e.g. TAC = 0 from 2010 onwards). Management plans No specific management objectives are known to ICES. ICES Advice 2012, Book 9 1

2 Biology Portuguese dogfish (Centroscymnus coelolepis) is a deep-water shark considered to be long-lived with a low productivity. The presence of all reproductive stages of this species in the area of the main mixed fishery (west of British Isles) implies that it is particularly vulnerable to exploitation. It is a live bearer and the pregnant female component of the stock is particularly vulnerable to exploitation. The stock structure and its dynamics along the Northeast Atlantic are still unknown. In the absence of such information, a single stock is considered for assessment purposes although smaller units may be appropriate for management. Environmental influence on the stock Deep-sea areas are considered to be comparatively stable. Given the low reproductive capacity of these stocks, recruitment is more dependent on female stock size than on environmental drivers. The fisheries Portuguese dogfish is an unavoidable bycatch taken in several mixed trawl fisheries and mixed longline fisheries. It is also taken as a bycatch in other fisheries, for example the anglerfish gillnet fishery. Fishing effort has declined since restrictions on deep-water fishing were put in place in 2007 (STECF, 2011). Effects of the fisheries on the ecosystem Deep-water bottom trawls impact the ocean floor, which implies potential damage to deep-water coral communities. As this fishery is part of mixed fisheries, any effort on Portuguese dogfish also impacts other commercial and noncommercial deep-water species. Quality considerations Many countries continue to report landings of Portuguese dogfish combined with leafscale gulper shark in categories such as siki sharks. Unless suitable data can be found to enable splitting of the catch data, historical catch levels will remain uncertain. In the past misreporting was considered a minor problem, but this is likely to have changed recently as a reaction to the EU restrictive measures adopted for deep-water sharks. Better estimates of discards are required for all deep-water fisheries. The actual sampling levels required by the EU Data Collection Framework (DCF) are considered inadequate for these stocks. Fishery-independent data are derived from surveys that take place in a restricted part of the whole distribution area considered for each of the two stocks. Scientific basis Assessment type Input data Discards and bycatch Indicators Other information Last benchmark in Working group report WGEF Trends-based. Commercial cpue indices. Not included in the assessment. Landings of Portuguese dogfish and leafscale gulper shark combined. Deep-water Scottish and Irish survey. 2 ICES Advice 2012, Book 9

3 Supporting information October 2012 ECOREGION STOCK Widely distributed and migratory stocks Portuguese dogfish (Centroscymnus coelolepis) in the Northeast Atlantic Reference points No reference points have been defined for this stock. Outlook for 2013 and 2014 No analytic assessment can be presented for this stock. Therefore, fishing possibilities cannot be projected. Precautionary approach There is no information to alter the perception of this stock as being depleted since the 2006 catch per unit effort estimates (ICES, 2006). Due to its very low productivity, Portuguese dogfish can only sustain very low rates of exploitation. The rates of exploitation cannot be quantified. Therefore, there should be no catches of Portuguese dogfish. Additional considerations Management considerations TACs only regulate the landings, and a low TAC on a low-value bycatch species could induce more discards. Because this species is caught as a bycatch in demersal fisheries, it would benefit from a reduction in the overall demersal fishing effort. Comparison with previous assessments and advice This is the first time ICES has given separate advice for this species. Until now, advice has been given for this species and leafscale gulper shark combined. No new assessment was performed in However, there is no information to alter the perception of the stock as being depleted. The advice is the same as was provided for 2011 and Sources ICES Report of the Working Group on Elasmobranch Fishes (WGEF), June 2006, ICES Headquarters. ICES CM 2006/ACFM: pp. ICES Report of the Working Group on Elasmobranch Fishes (WGEF), 3 6 March 2008, Copenhagen, Denmark. ICES CM 2008/ACOM: pp.. ICES Report of the Working Group on Elasmobranch Fishes, June 2012, Lisbon, Portugal. ICES CM 2012/ACOM:19. STECF Evaluation of Fishing Effort Regimes Deep Sea and Western Waters (STECF-11-12). N. Bailey and N. Mitrakis (Eds.), ISSN (online), ISSN (print), ISBN pp. ICES Advice 2012, Book 9 3

4 Figure Table Portuguese dogfish in the Northeast Atlantic. Biomass index (kg hr 1 ) from the coordinated Scottish and Irish deep-water surveys. Error bars denote std. error. Portuguese dogfish in the Northeast Atlantic. ICES advice, management, and landings. Year ICES Advice 1 Predicted catch corresp. to advice 1 Agreed TAC for deep-water sharks ICES Landings No advice Reduce exploitation No advice No advice Zero catch No new advice, same as for TAC = 0, prevent bycatch No new advice, same as for Zero catch No new advice, same as for Zero catch No new advice, same as for Zero catch No new advice, same as for Weights in tonnes. 1 Advice prior to 2013 was for Portuguese dogfish and leafscale gulper shark combined. 2 Combined landings for Portuguese dogfish and leafscale gulper shark. 4 ICES Advice 2012, Book 9

5 Table Portuguese dogfish and leafscale gulper shark in the Northeast Atlantic. ICES estimates of landings by area (in tonnes). ICES Advice 2012, Book 9 5