Sexual Mismatch Between Vessel-Associated Foraging and Discard Consumption in a Marine Top Predator

Joan Giménez*, Gavin E. Arneill, Ashley Bennison, Enrico Pirotta, Hans D. Gerritsen, Thomas W. Bodey, Stuart Bearhop, Keith C. Hamer, Stephen Votier, Mark Jessopp

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)
14 Downloads (Pure)


Sex differences in diet and foraging behaviour are common in sexually dimorphic species, often driven by differences in the cost of locomotion or ability to exploit different ecological niches. However, sex-specific foraging strategies also occur in monomorphic or slightly dimorphic species where the drivers are poorly understood. Here, we study sex differences in foraging of northern gannets (Morus bassanus), where females are only slightly heavier than males. Using concurrently tracked gannets (298 full foraging trips from 81 individuals) and fishing vessels across 5 years, we quantify individual-based vessel-associated putative foraging, and relate this to discard consumption. We found a significant positive relationship between time spent in vessel-associated foraging and discard consumption for both sexes. However, while females showed greater proportions of vessel-associated foraging than males, discarded fish contributed less to the diet of females in all years. These results contrast with previous suggestions that female gannets interact with vessels less often than males, and are consistent with competitive exclusion of females from trawler-associated discards. Our findings give insight into sexual differences in foraging behaviour in the absence of dimorphism that are necessary to predict their response to environmental and anthropogenic changes.

Original languageEnglish
Article number636468
Number of pages13
JournalFrontiers in Marine Science
Publication statusPublished - 15 Apr 2021

Bibliographical note

We would like to thank all those involved in fieldwork as well as the Neale family for permitting work on Great Saltee.

Funding: for 2010 and 2011 data was provided by the National Environment Research Council Standard Grant NE/H007466/1, and Beaufort Marine Research Award funded under the Marine Research Sub-Programme of the National Development Plan 2007?2013. Funding for 2017?2019 data was provided by the Irish Research Council (GOIPG/2016/503), and the Department of Agriculture, Fisheries, and the Marine FishKOSM project under grant (15/S/744). JG was funded by the Department of Agriculture, Fisheries, and the Marine FishKOSM project. GA was funded by the MarPAMM project supported by the EU?s INTERREG VA Programme, managed by the Special EU Programmes Body (SEUPB).


  • diet
  • fisheries
  • northern gannets
  • stable isotopes
  • tracking data


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