Advice June 2012

Transcription

1 Advice June 2012 ECOREGION STOCK Widely distributed and migratory stocks Ling (Molva molva) in Division Va Advice for 2013 and 2014 Based on the ICES approach for data-limited stocks, ICES advises that catches should be no more than tonnes. 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 ) Qualitative evaluation MSY (B trigger ) Precautionary approach (B pa,b lim ) Qualitative evaluation F (Fishing Mortality) Stable SSB (Spawning-Stock Biomass) Above poss. reference points Figure Ling in Division Va. Top: Indices from the Icelandic March groundfish survey : abundance of fish less than 40 cm (left) and biomass of fish 40 cm and larger (right). The shaded area shows ±1 standard error of the estimate. Bottom: Landings (thousand tonnes) (left) and estimates of trends in relative fishing mortality (F proxy = Yield / Survey biomass) (right). ICES Advice 2012, Book 9 1

2 The juvenile index was high in 2004 to 2010 and has decreased since then, though it remains higher than in The biomass index is at its highest level. Fishing mortalities have on average been lower since 2003 compared with those observed in the 1990s. Management plans No specific management objectives are known to ICES. Biology Ling is primarily fished in the depth range m, though it is also found at shallower depths. Ling in Division Va matures on average at a length of 75 cm, so a considerable proportion of catches consists of immature ling. The life history traits are in line with other members of the gadoid family, suggesting it is less vulnerable to fishing mortality than typical deep-water species. The fisheries Approximately 68% of the annual landings in Division Va are caught in a mixed fishery by longliners and the remainder as a bycatch, mainly by trawlers which are primarily targeting cod. Catch distribution Total landings (2011) are 9.6 kt (68% longline, 27% trawl, and 5% gillnet and Danish seine). Quality considerations The assessment is based on trends in the Icelandic March groundfish survey. The trends are similar to those of the October survey. 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 the 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 Survey trends-based assessment. March Icelandic groundfish survey and data from commercial catches. Not included in the assessment. None. None. WGDEEP 2 ICES Advice 2012, Book 9

3 Supporting information June 2012 ECOREGION STOCK Widely distributed and migratory stocks Ling (Molva molva) in Division Va Reference points There is no analytical basis on which to calculate biological reference points. During the period 2003 to 2007 (when the stock was increasing) the mean value of F proxy (total catch/survey biomass) was 1.5. An F proxy value of 1.5 is in the lower range of values observed in the fisheries over the time period when no detrimental effects were observed in the stock dynamics. This value can therefore be considered to be an appropriate advisory F proxy upon which to base catch advice. The scale of F proxy is arbitrary and based on total catches survey divided by biomass estimates. 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 For data-limited stocks with reliable abundance information from fisheries-independent data and a target F proxy, where abundance is considered above MSY B trigger, ICES uses a harvest control rule that requires calculation of catches to be based on the F proxy target multiplied by the most recent survey biomass estimates. For this stock the F proxy of 1.5 is applied as a factor of the average of the most recent survey biomass estimates (average of 2011 and 2012), resulting in catch advice of no more than t. This catch advice is within 20% of the last three years catch and a 20% precautionary buffer is not applied because the stock has increased by more than 50% in the last two years compared with the three preceding years. Additional considerations Surveys indicate that the overall biomass is currently relatively high in the available time-series (Figure ). An exploratory analytical run based on the GADGET model indicates that the stock has been increasing over time and that fishing mortalities have been decreasing. The overshoot in the set TAC for ling for the Icelandic fleet is a result of the allowance, albeit limited, for exchanging the quota (individual transfer quota, ITQ) of one species for another. The allowance has the objective of limiting discarding and misreporting. However, for relatively small stocks with small TAC, this may result in serious overfishing in the long term. Source 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. ICES Advice 2012, Book 9 3

4 Table Ling in Division Va. ICES advice, management, and landings. Year 1 ICES Advice 1 Predicted catch corresp. to advice 2 ICES landings Division Va 2 TAC Icelandic Division Va 3 ICES landings Division Va /04 30% reduction on fishing effort /05 Biennial /06 30% reduction on fishing effort /07 Biennial /08 Maintain catches at level /09 Biennial /10 Constrain catches to average 2010/11 Biennial /12 Same advice as previously /13 F proxy target /14 No new advice, same as Weights in thousand tonnes. 1 National fishing year ending on 31 August. 2 Calendar year (refers to second year in fishing year). 3 National fishing year. 4 Single advice for ling in Northeast Atlantic. 4 ICES Advice 2012, Book 9

5 Table Ling in Division Va. Landings since 1950 (tonnes). Source: STATLANT database. YEAR BELGIUM FAROE FRANCE GERMANY ICELAND NORWAY UK TOTAL Cont. ICES Advice 2012, Book 9 5

6 Cont d Year Belgium Faroe France Germany Iceland Norway UK Total * *Preliminary. Table Ling in Division Va. Survey biomass estimates from the Icelandic March survey, total yield, and F proxy (Yield/Survey biomass). Year Survey Yield F proxy biomass ICES Advice 2012, Book 9