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Effects of changes in fishery discarding rates on seabird communities

Discbird will provide a detailed study on the impact of changes in discarding rates on seabird communities. This will permit management of fisheries to be designed to minimise adverse impacts on seabird communities, consistent with the stated objective of FAO, ICES and national governments to reduce discarding in order to manage fish stocks for sustainable fisheries. Research into seabird ecology shows that reproductive effort in the breeding season can affect winter survival, and that winter feeding conditions can influence body condition and hence breeding success in the subsequent summer. In order to take account of such influences across the seasons, Discbird will use state-of-the-art technological methods to study seabird winter migrations. Biochemical methods (stable isotope analysis and fatty acid analysis) will be used to measure dependence on discards, and the influence on subsequent body condition and breeding success, of feeding on discards in winter (when discards tend to be most heavily exploited by seabirds). Long-term data sets on discard quantities and seabird diet composition will be compared in order to assess the ways in which seabird diets are altered by changes in technical measures, fishing effort or stock size/recruitment affecting amounts of discarding.

The objective is to quantify the impact of change in fishery discarding rates on seabird communities, in order to inform fishery discard management better. The study will determine whether winter-at-sea distribution of selected scavenging seabird species are influenced by distribution of fisheries generating many discards, and quantify how feeding on discards in winter affects seabird demography through influences on adult body condition, breeding and survival. Existing databases will be used to determine how changes in discard rates in well-documented fisheries in the northwest North Sea and western Mediterranean have influenced seabird diet, demographic parameters, and populations over many years. They will also be used to see how changes in discarding rates are affecting the predatory impact of scavenging seabirds on smaller seabird species, and hence altering seabird community structure. The aim is to provide a better understanding of scavenging seabird ecology that can be used to inform policy. New state-of-the-art technologies (satellite tracking, geolocational data loggers, stable isotope and fatty acid biomarkers) will be used to quantify the importance of discards in seabird population ecology, related to measures of breeding success. High quality archived data on breeding ecology will be related to the best data sets on discarding rates.

Progress to Date
The project is progressing well and details are available from the website:

Captive gulls were fed defined diets to investigate the fatty acid and stable isotope signatures resulting from specific fish stenophagous diets and rates of change on switching diet. This work has been completed and most resulting samples have been analysed. Preliminary indications are that the diets provided clear differences in signatures, and that the sampling protocol has identified the rates of change of signature resulting from dietary switches. This work is in the process of being analysed and written up for publication. It will provide a baseline for the interpretation of fatty acid and stable isotope signatures from free-living scavenging seabirds. Fieldwork has been completed for one seabird breeding season (summer 2002), investigating scavenging seabird migrations, diet, breeding success and body condition as well as impacts on other species in the community resulting from predation.
Large numbers of regurgitated pellets and chick and adult regurgitated food samples have been collected, and prey items identified. Data on diet have been added to databases that have been set up to record historical data on diet composition. Compilation of databases of historical data on population size and breeding success of scavenging seabirds is well underway. Large numbers of fish, blood and feather samples have been collected from Shetland and the western Mediterranean for the study of fatty acid and stable isotope signatures of wild birds and their foods. These samples are currently being analysed and this work will soon be completed.


Scientist responsible for the project

Graham Kerr Building
G12 8QQ Glasgow
United Kingdom (The) - GB

Phone: +44 141 330 3560
Fax: +44 141 330 5971


Project ID QLRT-2000-00839
Organisation University of Glasgow
Area 5.1.2
Start date 02 January 2002
Duration (months) 42
Total cost 1 897 839 €
Total EC contribution   1 378 983 €
Status Ongoing
Web address of the project

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