Objective The aim of the project is the evaluation of the impact of various bycatch species on the survival of juveniles of the important exploited species during the first year of life (before the age of recruitment). This component is an addition to the ICES Stomach Sampling Programme 1991, which is directed primarily at consumption of commercially important predator species, and will allow a comparison of the relative impact of different components of the marine ecosystem on the recruitment of different species. The contract is aimed at an evaluation of the impact of various bycatch fish species on the survival of the important exploited species during the first year of life. Although there is a clear ultimate connection with management issues the research carried out covered only aspects of data collection and primary analysis. The results obtained enable extension of existing multispecies assessment models to incorporate the effects of other predator species and may cast new light on recruitment processes.The research was directly linked to another project aimed at an evaluation of the food composition of 5 commercially important predator species and therefore did not require extra research vessel effort. In total 25 000 stomachs of bycatch species were collected. A priority was set and only stomachs of 12 000 grey gurnard and 4000 rays were selected for analysis.The results indicate that the food of grey gurnards consists largely of a variety of commercially important species, particularly gadoids and sandeels. The different ray species vary significantly in the size at which they shift from feeding mainly on crustaceans to fish. The extent to which the rays feed on commercially important species is difficult to evaluate, because only a small component of the fish found in stomachs could be identified to the species level. More detailed analyses of the data are required to solve this problem.On the basis of the results obtained and estimated biomass figures from the literature, it is concluded that both grey gurnard and starry ray consume large quantities of juvenile fish. Other ray species appear to be relatively less important. However, a final evaluation will only be possible when these data are incorporated in multispecies assessment models.The work will include the following phases: collection of stomachs of a variety of species at sea; analysis of the stomach contents in the laboratory; processing of the data for multispecies analysis; and evaluation. The bycatch species to be considered include horse mackerel (Trachurus trachurus), grey gurnard (Eutrigla gurnardus), rays (Raja species), dogfish (Squalus acanthias), turbot (Scophthalmus maximus), brill (Scophthalmus rhombus), sandeels (Ammodytidae) and greater sandeel (Hyperoplus lanceolatus). In the first phase, the task of collecting around 10000 stomachs of bycatch species at sea will be equally split among the 3 proposers. The total labour involved will be approximately one and a half years for each institute (excluding the standard species considered within the Stomach Sampling Project). In the second phase, with the exception of various species of rays (Raja species), the samples will be sent to Ijmuiden and the main contractor will be responsible for the analysis and processing of the data. The rays will be analysed by the first subcontractor. The analysis of stomach contents requires extensive experience in the recognition of remains of different stages of digestion and can in practice only be done satisfactorily by scientists. In the third phase, before the results can be processed in a standard way, the available software has to be revised so as to accommodate specific problems raised by individual species. In the fourth phase, the evaluation of the results includes the preparation of tables of relative food composition by quarter, area and age group, which can be used directly as input for multispecies assessment. However, the final report to the EEC will include a tentative description of the impact of the different predatory fish species in the North Sea. Fields of science natural sciencescomputer and information sciencessoftwarenatural sciencesbiological sciencesecologyecosystemsnatural sciencesbiological scienceszoologyichthyologyagricultural sciencesagricultural biotechnologybiomass Programme(s) FP2-FAR - Community research and coordination programmes (EEC) in the fisheries sector, 1988-1992 Topic(s) Data not available Call for proposal Data not available Funding Scheme Data not available Coordinator Rijksinstituut voor Visserijonderzoek (RIVO) EU contribution No data Address Postbus 68, Haringkade 1 1970 AB Ijmuiden Netherlands See on map Total cost No data Participants (2) Sort alphabetically Sort by EU Contribution Expand all Collapse all DANMARKS FISKERI OG HAVUNDERSOEGELSER-DIFMAR-CHARLOTTENLUND Denmark EU contribution No data Address Charlottenlund See on map Total cost No data Scottish Office Agriculture, Environment and Fisheries Department United Kingdom EU contribution No data Address Victoria Road AB11 9DB Aberdeen See on map Total cost No data
