Fisheries-independent survey data

4.2.4. Please identify strengths and weakness of each survey and identify if and how they could be improved.

See CS1c (blue ling) report.

4.2.5.If any surveys have been terminated within the last 10 years please explain why.

4.2.6.Are any new surveys being considered? If so please describe.

New surveys are being considered by WGNEACS, see CS 1c report.

4.2.7.Available survey abundance indices available for your stock (tables and figures) and comment on their strengths and weaknesses

An index was available from a Scottish deep-water survey to the west of Scotland The fish community of the continental shelf slope to the northwest of Scotland has been surveyed by Marine Scotland - Science [formerly Fisheries Research Services, (FRS)] since 1996, with strictly comparable data available between 1998 and 2008. This has focussed on a core area between 55-59°N, with trawling undertaken at depths ranging from 300 to 1900m with most of the hauls being conducted at fixed stations, at depths of around 500m, 1000m, 1500m and 1800m. Further hauls have been made on seamounts in the area, and on the slope around Rockall Bank, but these are exploratory, irregular and not included in the survey dataset. This survey was conducted biennially, in September, until 2004, since when it has been carried out on an annual basis. In total, the data set comprises 233 valid hauls. From 1998 to 2008 the bottom trawl was rigged with 21” rock-hopper ground gear, however in 2009, a switch was made to lighter ground gear, with 16” bobbins (ICES 2010b). The trend in annual mean CPUE is shown in figure 4.2.7a.

Abundance index of roundnose grenadier and other macrourids were published by Neat and Burns (2009). For roundnose grenadier the abundance and biomasss indices showed no clear trend over 2000-2008. Ther was also no change in mean length but a slight change in maximum length. Overall, the results from this study demonstrated that the grenadiers from the NE Atlantic have not declined in the past ten years.

and the relative stability observed across seven macrourid species was suggested to reflect the introduction TACs and a management regime and that this may have been sufficient to prevent the further decline of the grenadier fishes. Amongst the smaller macrourids analysed in this study, 2 species increased in abundance in the other were stable, the authors noted that the smaller macrourids have a much shorter life span than the roundnose grenadier.
A Spanish survay on the Porcupine banks provides abundance indices for shelf and upper slope species. In the contaxt of Deepfishman, this survey provides a useful index for the greater forkbeard. In this survey the recruitment of greater forkbeard in well visible and the time-series suggest than a strong recruitment occurred in 2003 (Figure 4.2.7c). Abundance indices are clearly impacted by this strong recruitment as the abundance in number peaked in 2003 and the biomass in following growth. This survey data seem of major interest for the greater forkbeard as in might both allow to validate growth of the species.

For the same species, shelf surveys carried out under DCF by France in the Celtic Sea, Spain and Scotland also provide abundance indices and length distribution from which trecruitment indices could be derived. Total abundance may not be available from these surveys that are restricted to bottom shallower than 600 m. nevertheless, the usefulness of survey indicators from surveys carried out under DCF might be considered. In the context of DEEPFISHMAN, this applies to greater forkbeard only.

Figure 4.2.7a. Abundance index of blue based upon the Scottish Deep-water Survey – trend in annual mean CPUE (± 1 s.e.)

Figure 4.2.7c. Mean stratified length distributions of Phycis blennoides in Porcupine surveys (2001-2009)

4.2.8. Aspects of fisheries-independent survey data (quality, temporal and spatial extent, time series, availability, accessibility, flow) that [a] impact on assessments and/or [b] affect ability to provide timely fisheries advice to managers.