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

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Abstract

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
JournalFrontiers in Marine Science
Volume8
DOIs
Publication statusPublished - 15 Apr 2021

Keywords

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

ASJC Scopus subject areas

  • Oceanography
  • Global and Planetary Change
  • Aquatic Science
  • Water Science and Technology
  • Environmental Science (miscellaneous)
  • Ocean Engineering

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