Advice June 2012

Transcription

1 Advice June 2012 ECOREGION STOCK Widely distributed and migratory stocks Blue ling (Molva dypterygia) in Division Vb and Subareas VI and VII Advice for 2013 and 2014 Based on the ICES approach for data-limited stocks, ICES advises that catches should be no higher than 3900 t in Existing management measures should be continued. Spatial management to prevent targeted fishing on spawning aggregations should be expanded to cover spawning areas in Division VIb. This is the first year ICES is providing quantitative advice for data-limited stocks (see Quality considerations). 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) Below target Undefined SSB (Spawning-Stock Biomass) Unknown, B trigger undefined Undefined Increasing International landings (tonnes) * VII VI Vb Harvest rate , , ,000 50, Total Biomass (tonn Fishing mortality Total abundance (millions Figure Blue ling in Division Vb and Subareas VI and VII. Top left: Landings (thousand tonnes). Top right: Harvest rate and total biomass (solid line) from stock reduction analysis (SRA, FL aspm ). Bottom left: Fishing mortality from the MYCC model. The blue shaded area depicts F MSY proxies from F = 0.12 to Bottom right: Total abundance (ages 9+) from MYCC. The stock reduction analysis (SRA) shows a large decrease in biomass between 1970 and The SRA (based on abundance indices and landings) and the multi-year catch curve (MYCC; based on age composition and landings) models both indicate decreasing fishing mortality since , below possible F MSY proxies and increasing biomass. This is consistent with the observed increase of the mean size in landings. ICES Advice 2012, Book 9 1

2 Management plans No specific management objectives are known to ICES. Biology Blue ling is a gadoid species that grows much faster than most deep-water species. It is vulnerable to exploitation because fisheries can target the spawning aggregations. The fisheries The main fisheries are those by Faroese trawlers in Division Vb and French trawlers in Subarea VI and, to a lesser extent, Division Vb. Total international landings from Subarea VII are very small, as are bycatches in other fisheries. Landings by Faroese trawlers are mostly taken in the spawning season. Historically, this was also the case for French trawlers fishing in Division Vb and Subarea VI. However, in recent years blue ling has been taken mainly as a bycatch in French trawl fisheries for roundnose grenadier and black scabbardfish. Catch distribution Total catches (2011) were 3 kt, where 99% were landings, <1% discards, 0% industrial bycatch, and 0% unaccounted removals. Effects of the fisheries on the ecosystem Deep-water bottom trawls impact the ocean floor, causing potential damage to deep-water coral communities. This is mitigated by closed areas to protect vulnerable marine ecosystems (VMEs). As this fishery is part of a mixed fisheries, any effort on blue ling also impacts other commercial and non-commercial deep-water species. Quality considerations All available information suggests that discarding in French fisheries is not significant (discards <1%). Other fisheries may be constrained by quotas that lead to some discarding, and the extent of discarding is unknown for some fleets. Age estimation was resumed in France through the EU Data Collection Framework (DCF), after a disruption from Age estimation requires accurate laboratory equipment and optics to read the thin growth increments from thin otolith slices. Age estimates are still not validated, and an age-reading workshop would be useful. The numbers of blue ling captured in the Scottish and Irish survey are small and the depth of peak abundance is not sampled. The methods applied to derive quantitative advice for data-limited stocks are expected to evolve as they are further developed and validated. The harvest control rules are expected to stabilize stock size, but they may not be suitable if the stock size is low and/or the stock overfished. Scientific basis Assessment type Input data Discards and bycatch Indicators Other information Working group report Stock Reduction Analysis (SRA), a model fitted to catches and abundance indices; Multi- Catch Curves (MYCC), a model fitted to age composition and total catch in order to estimate annual total mortality (Z). International landings ; landings per unit effort (lpue) from logbooks and French tallybooks; Faroese, Scottish, and Irish surveys; age composition of French landings ( and ). Not significant. Biomass indices from commercial lpues, mean length in French and Faroese landings, survey indices. None. WGDEEP 2 ICES Advice 2012, Book 9

3 Supporting information June 2012 ECOREGION STOCK Widely distributed and migratory stocks Blue ling (Molva dypterygia) in Division Vb and Subareas VI and VII Reference points Preliminary investigations undertaken by ICES in 2012 indicate that for an assumed natural mortality of 0.18, an appropriate proxy for F MSY lies within the range of Outlook for 2013 and 2014 No analytical assessment is available for this stock. Therefore, detailed management options cannot be presented. ICES approach to data-limited stocks Two independent stock assessment models return similar views that the stock was overexploited, with fishing mortality showing a peak in 2000 and then decreasing. These models indicate that stock abundance has been increasing since 2003 or The history of the exploitation is longer than most time-series of data, only landings time-series could be reconstructed back to 1966, i.e. early times of the fishery. The time-series of length distribution starts from the late 1980s and landings per unit of effort (lpue) from tallybook records in However, the SRA model provides an estimate of the biomass in the late 1960s when exploitation was very low. This estimate can be regarded as a virgin biomass estimate, a reference situation not usually available for demersal fish stocks. The stock abundance has increased by a factor of 1.7 since 2002 according to SRA, and 2.8 since 2004 according to MYCC. However, the absolute level is estimated at about 25% of the unexploited level according to SRA. Fishing mortality in the period 2008 to 2011 was well below all suggested F MSY proxy values. However, current biomass in relation to B trigger is unknown and there is a possibility that the stock is below this point. It would therefore not be appropriate to allow F to increase to F MSY until the biomass relative to B trigger can be assessed. Maintaining recent catches (average of landings 2008 to 2011) would be expected to result in increasing SSB. This would imply a catch of 3.9 kt in Blue ling is susceptible to sequential depletion of spawning aggregations. High landings were caught at spawning time until the 2000s. Current spatial measures to protect spawning aggregations should therefore be maintained, and new spatial measures should be identified and implemented where appropriate, in particular in international waters in Divisions Vb and VIb. Additional considerations The EU management unit for this stock was expanded in 2011 to include EU and international waters of Division Vb. As a consequence the assessment and management areas are now consistent. The EU further introduced a in Subarea XII, so that all areas where blue ling occur are now covered by s. The western part of Hatton Bank (ICES Division XIIb) is contiguous with the eastern part of Hatton Bank (ICES Division VIb). Catches in ICES Division XIIb are likely to come from the same stock as catches in Division Vb and Subareas VI and VII. However, catch data from Division XIIb are not considered reliable and would probably add noise to the assessment. In 2009, EU protection areas were introduced for spawning aggregations of blue ling on the edge of the Scottish continental shelf and at the edge of Rosemary Bank (both in Division VIa). Entry/exit regulations apply and vessels may not retain more than 6 t of blue ling from these areas per trip. When retaining 6 t vessels must exit the area and are not allowed to re-enter such areas before landing. These vessels may not discard any quantity of blue ling. Consequently, there remains some directed fishing for blue ling. The effectiveness of these protection areas in reducing catches from directed fisheries should be examined. Some spawning grounds on the eastern and northeastern parts of Hatton Bank currently remain open to fishing. Some areas are closed to bottom fishing gears on Rockall and Hatton Bank to protect cold-water corals. It should be investigated whether the extent of protection afforded to spawning aggregations of blue ling is adequate, or whether it needs to be extended further. ICES Advice 2012, Book 9 3

4 1.4 Mean length in French landings Biomass index mean length (cm) Q1 Q2 Q3 Q Figure Blue ling in Division Vb and Subareas VI and VII. Left: Annual mean standardized lpue of blue ling from French logbook data, relative index. Middle: Annual mean standardized lpue of blue ling from French tallybook data, relative index. Right: Standardized time-series of lpue from logbook data. Because of restricted opportunities for fishing in 2011, the value of the catches in 2011 may be depressed. Sources ICES Report of the ICES Advisory Committee, ICES Advice, Book pp. ICES Report of the Working Group on the Biology and Assessment of Deep-Sea Fisheries Resources (WGDEEP), 29 March 05 April 2012, ICES Headquarters, Copenhagen. ICES CM 2012/ACOM:17. 4 ICES Advice 2012, Book 9

5 Table Blue ling in Division Vb and Subareas VI and VII. ICES advice, management, and landings. ICES Advice Predicted catch corresp. to advice EU Division Vb (Faroese waters) 1 EU Subareas VI and VII Faroese Subareas VI and VII Norway Divisions IIa and Vb, and Subareas IV, VI, and VII ICES landings Division Vb and Subareas VI and VII 2003 No direct fisheries Biennial No direct fisheries Biennial No direct fisheries Biennial No direct fisheries Biennial No direct fishery and effort to limit bycatch. A reduction in catches should be considered No new advice, same as Average catch to No new advice, same as Weights in thousand tonnes. 1 for ling and blue ling. Including a bycatch of roundnose grenadier and black scabbardfish. 2 Advice for blue ling in the Northeast Atlantic (not split by different assessment units). ICES Advice 2012, Book 9 5

6 Table a Blue ling in Division Vb and Subareas VI and VII. ICES estimates of landings, used for assessment (tonnes). Faroes France Germany Norway E & W Scotland Ireland Russia Lithuania Poland Iceland Estonia Spain Total * *Preliminary. 6 ICES Advice 2012, Book 9

7 Table b Blue ling in Division Vb and Subareas VI and VII. Official STATLANT landings from ICES database (tonnes). Estonia Faeroe Islands France Germany Iceland Ireland Lithuania Norway Poland Russian Federation Spain UK Total ICES Advice 2012, Book 9 7