Report of the Working Group for North-east Atlantic Continental Slope Survey (WGNEACS)
| Type | Expertise | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Date | 2011-06-16 | ||||||||
| Language | English | ||||||||
| Ref. | ICES CM 2011/SSGESST:15 REF. SCICOM, ACOM | ||||||||
| Other localization | http://www.ices.dk/publications/our-publications/Pages/CM-documents.aspx | ||||||||
| Author(s) | ICES Advisory Committee on Fishery Management | ||||||||
| Contributor(s) | Lorance Pascal |
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| Sponsor | CIEM | ||||||||
| Abstract | The present report was prepared by the Working Group on the North-east Atlantic Continental Slope Survey (WGNEACS) in ICES, Copenhagen, from 14–16 June 2011. WGNEACS reviewed the possibilities provide the following community indices for deep-water species; i)Proportion of fish larger than the mean size of first sexual maturation, ii) mean maximum length across all species found in research vessel surveys. iii) 95th % percentile of the fish length distribution observed in research vessel surveys. In deep-water surveys, length frequency data are widely available, however information on age and reproductive state are available for fewer species. In addressing WGNEACS thought it was useful first to identify those species for which this information is available. Also a case study regarding i-iii for roundnose grenadier was performed. Last’s years meeting identified three subgroups of existing deep-water surveys and new survey requirements (proposals) that were grouped by geographical area, a Nordic, a central and a southern subgroup. At this year’s meeting, these three subgroups received a set of specific terms of references to work with. The Nordic subgroup dealt with deep-water trawl surveys that are currently undertaken by Norway, Iceland, Faroe and Greenland. The subgroup continued the evaluation on the sampling protocols of the existing Nordic deep-water surveys with the aim to standardize them as much as possible. Similarities and differences in sampling design and protocols were highlighted. A set of recommendations were made to the Nordic national laboratories on last meeting in order to improve coordination of surveys. The state of this coordination was evaluated. To share data and initiate joint data analysis and research, a data exchange format was agreed upon at the 2010 meeting and abundance data from four target species (Greenland Halibut, Greater Silver smelt, Beaked Redfish and Roundnose Grenadier) were combined from all Nordic deep-water surveys. Standardized swept-area estimates were updated at the current meeting, and mapped to evaluate the spatial coverage of the surveys in relation to species distribution and to identify any gaps. The central survey subgroup concentrated on providing cpue estimates using existing data for selected species as well as the corresponding distribution plots for these species. Three species from the central survey area were considered to be suitable candidates for this. Roundnose grenadier, greater forkbeard and black scabbard. A fourth species, blue ling was also considered although it was decided after discussion that it was not an appropriate candidate for index calculation as the numbers caught on the surveys generally are very low. This issue was researched further using GAM models of haul-by haul (tally book) commercial blue ling catch data from French commercial trawlers. These were used to assess the depth distribution of exploited blue ling to the West of Scotland. CPUE estimates were provided for both abundance and biomass and in the case of greater forkbeard and black scabbard these were calculated using the survey data from a single depth strata where peak abundance within the sampled survey depth had been identified. There has been no intersessional work completed regarding the variance of the individual surveys within the central area and this will recommence once the new expanded survey proposal is implemented in 2013/14. Since there have been no new surveys in 2010 there is no new data. The ToRs for the southern area raise a number of issues. However, there is currently no survey able to produce abundance indices for the target species (Aphanopus carbo) and the deep-sea sharks mentioned in the ToRs for the southern Areas. The southern subgroup dealt with existing and proposed surveys in the southern area (IX and X). The subgroup proposed longline deep-water surveys off mainland Portugal and in the Bay of Biscay. The main objective for assessment in the southern area is to produce relative index of abundance and other population indicators for black scabbardfish, deep-water sharks and other species caught in sufficient numbers (e.g. red sea bream, bluemouth and greater forkbeard). Abundance indices are essential to get information needed for assessment of the black scabbardfish stock in southern areas. The group considered that as there are two major fisheries for this black scabbardfish stock, there is a priority to collect abundance indices in the area of these two fisheries (southwest of Portugal and around Madeira). Additionally to estimate density throughout the area of distribution, surveys would be needed along all the Portuguese slope, further northwest of Galicia (Spain) and in the Bay of Biscay, as well as along the slope of the gulf of Cadiz. The slope of all these areas are hard rocky bottoms with bottom topography that prohibits trawl surveys with random sampling. Thus the group considered that the appropriate way forwards to obtain abundance indices in the southern area is to develop longline surveys. |
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