@article {8049, title = {Contribution of toothfish depredated on fishing lines to the energy intake of killer whales off the Crozet Islands: a multi-scale bioenergetic approach}, journal = {Marine Ecology Progress Series}, volume = {668}, year = {2021}, month = {Dec-06-2022}, pages = {149 - 161}, abstract = {Fisheries modify prey availability for marine predators by extracting resources but also by providing them with new feeding opportunities. Among these, depredation, which occurs when predators feed on fish caught on fishing gear, is a behavior developed by many species as a way to acquire food through limited foraging effort. However, the extent to which depredated resources from fisheries contribute to the energetic requirements and affect the demography of depredating individuals is unknown. We investigated the contribution of Patagonian toothfish Dissostichus eleginoides depredated on longlines to the energetic requirements of killer whales Orcinus orca around the Crozet Islands (southern Indian Ocean) over the period 2007-2018. Our results indicate that during days when depredation occurred, depredating individuals fulfilled on average 94.1\% of their daily energetic requirements with depredated toothfish. However, the contribution varied from 1.2 to 13.3\% of the monthly energetic requirements and from 2.4 to 8.8\% of the yearly energetic requirements of the total population. Together, these findings suggest that intake of depredated toothfish can be substantial at a fine scale (daily and individually), potentially leading to temporary provisioning effects and changes in predation pressures. These effects become minor (\<10\%), however, when considering the full population over a whole year. The contribution of depredated fish to the annual energetic requirements of the population has increased in recent years, likely due to larger fishing quotas and greater opportunities for whales to depredate, which stresses the importance of accounting for depredation in ecosystem-based management of fishing activity.}, issn = {0171-8630}, doi = {10.3354/meps13725}, url = {https://www.int-res.com/abstracts/meps/v668/p149-161/}, author = {Faure, Johanna and Clara P{\'e}ron and Nicolas Gasco and Massiot-Granier, F{\'e}lix and Spitz, J and Guinet, C and Tixier, P} } @article {4724, title = {Multi-approach analysis to assess diet of harbour porpoises Phocoena phocoena in the southern North Sea}, journal = {Marine Ecology and Progress Series}, volume = {563}, year = {2017}, month = {01/2017}, pages = {249-259}, abstract = {

Over the past decade, the distribution of harbour porpoises Phocoena phocoena has undergone a southward shift in the North Sea, which has led to an increase in the number of stranded porpoises in its southern part. Since the changes in distribution and relative abundance of porpoises may be linked to the changes in prey availability, the aim of the present work was to investigate whether any changes in the feeding habits of harbour porpoises along the North Sea occurred in the past decade. The diet of harbour porpoises stranded along the southern North Sea (northern France and Belgian coast) was assessed through 3 complementary methods: stomach content analysis, stable isotopes (carbon and nitrogen) analysis determined from muscle samples, and fatty acids analysis determined from blubber samples. Fatty acid patterns and stable isotope values from 52 porpoises were compared to 14 potential prey species collected from the southern North Sea. Our results showed that the diet of porpoises along the southern North Sea comprises fish species that are among the most abundant and widely distributed in the area, except for the sardine Sardina pilchardus that appeared to be a new potential prey. Moreover, our results suggested that the decline in sandeel (Ammodytidae) in the northern parts of the North Sea along with the re-invasion of the southern North Sea by sardine species might affect the distribution of harbour porpoises.

}, author = {Mahfouz, C and Tarik Meziane and Henry, F and Abi-Ghanem, C and Spitz, J and Jauniaux, T and Bouveroux, T and Khalef, G} }