|Source||ICES Scientific Reports/Rapports scientifiques du CIEM (2618-1371) (ICES), 2020 , Vol. 2 , N. 26 , P. 73pp.|
The Workshop on Better Coordinated Stomach Sampling (WKBECOSS) reviewed existing stomach sampling programmes and associated guidelines. Programmes were categorized as i) stomach sampling for multispecies modelling, ii) stomach sampling for Marine Strategy Framework Directive (MSFD) indicator measurement and development, iii) stomach sampling for ecosystem modelling, iv) stomach sampling for process-related studies driven by fundamental research questions and v) long-term time series of stomach sampling to understand trophic impacts related to large-scale environmental change, such as global warming. While sampling approaches to meet these different objectives may be linked, the demands for sampling intensity and stomach analyses are fundamentally different. Consequently, findings based on the different data that result will vary in temporal, spatial and organisational scale from studies on consumption rates to analyses of ecosystem connectivity and structure. Stomach sampling was considered particularly relevant for providing inputs to multispecies models and Ecosystem Status (i.e. MSFD) indicators. For both purposes, detailed sampling best practices exist and, in general, are appropriate. However, a small amount of additional sampling, including of areas outside those strictly included in established surveys, diel and seasonal/ monthly variation sampling, and of under-targeted species, would help assess whether current sampling programmes adequately account for predator trophic dynamics in currently evaluated areas. Currently, few national collection programmes for stomach data are coordinated with others in the ICES region, and no common EU stomach sampling is ongoing. Stomach sampling for multispecies modelling, e.g. ICES Year of the Stomach, has been irregular and typically focussed on relatively few commercially important species, with the aim of estimating predator-prey selectivity. MSFD food web indicators, such as functional groups or mean trophic level, require information across a broader range of taxa, including rare and minor species not of commercial interest, because their aim is to provide evidence of change in structure and functioning within and across ecosystems. In the absence of coordinated international sampling, indicator development has often relied on data collated across projects, such as held on Fishbase and DAPSTOM (integrated database and portal for fish stomach records). Stable isotope analyses are an additional tool to measure mean trophic level. They provide unique information in relation to stomach contents and genetics because they incorporate a longer-term view of predator diet, albeit with less resolved information on prey identity that can be challenging or impossible to interpret. Genetic methods show promise in identifying quickly digested prey (e.g. jellyfish), resources of intermediate consumers, lower trophic levels and larvae whose prey may be small, not ingested whole and therefore not readily identifiable using traditional methods. Examples of consumers whose diets could be better resolved using genetic methods include planktivorous fishes, cephalopods and crustaceans. Information on their diets will be key to broadening our understanding of ecosystem structure and functioning. At present, these genetic methods do not provide information on cannibalism or age of prey, and are limited in estimating prey weight and size, and are thus not yet suitable for delivering the data needs for multi-species models and estimating mean trophic level.
ICES (2020). Workshop on Better Coordinated Stomach Sampling (WKBECOSS). ICES Scientific Reports/Rapports scientifiques du CIEM, 2(26), 73pp. Publisher's official version : https://doi.org/10.17895/ices.pub.5991 , Open Access version : https://archimer.ifremer.fr/doc/00708/82010/