Gannets are not attracted to fishing vessels in Iceland-potential influence of a discard ban and food availability

Bethany L. Clark*, Freydís Vigfúsdóttir, Mark J. Jessopp, Julian M. Burgos, Thomas W. Bodey, Stephen C. Votier

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)
4 Downloads (Pure)

Abstract

Fisheries produce large amounts of waste, providing food subsidies for scavengers. Discards influence seabird movement, demography and community structure, but little is known about seabird-fishery interactions where discarding is banned. Here, we investigate how northern gannets Morus bassanus respond to fishing vessels in Iceland, where discarding commercial species is illegal, but birds may still access bait, offal, or catch. We GPS-tracked 82 foraging trips for 36 breeding gannets from two colonies (Skrúður and Hellisey) and obtained time-matched vessel locations. We classified bird behaviour using Hidden Markov Models and then tested the effect of vessel distance on behavioural state-switching using multi-state Markov models. Fishing vessels were present during 94% of foraging trips. However, the likelihood of gannets switching from travelling to foraging was unaffected by vessel proximity, regardless of gear type or activity. When encountering vessels, gannets rarely foraged but instead were more likely to continue travelling. When controlling for population size, gannet foraging trips at both colonies were shorter than expected, suggesting favourable conditions. The lack of behavioural responses to vessels among Icelandic gannets is likely driven by the discard ban and availability of pelagic fishes. Our findings have implications for understanding bycatch risk and the consequences of discard reforms.

Original languageEnglish
Pages (from-to)692-700
Number of pages9
JournalICES Journal of Marine Science
Volume77
Issue number2
Early online date4 Dec 2019
DOIs
Publication statusPublished - 1 Mar 2020

Bibliographical note

BLC was supported by a NERC GW4+ Doctoral Training Partnership studentship from the Natural Environment Research Council [NE/L002434/1]. We thank Ólafur Torfason, Niall Tierney, and Rachel Stroud for fieldwork assistance in Skrúður, and Mamma-Rósa for food and housing in Vestmannaeyjar. We thank the Hellisey hunting club for the use of cabin and assistance with boat trips to Hellisey. We thank Filipa Samarra, Miguel Neves, Gary Haskins, and team members in the Icelandic Orca Project for boat trips to Hellisey. We thank Lucy Hawkes, David Pascall, Alice Williams, Richard Phillips, Brendan Godley and all reviewers for constructive comments on the manuscript. The GPS tracking data are available through the BirdLife International Seabird Tracking Database (http://www.seabirdtracking.org).

Keywords

  • behavioural response
  • biologging
  • foraging
  • GPS tracking
  • Morus bassanus
  • northern gannet
  • Predictable Anthropogenic Food Subsidies (PAFS)
  • scavenging
  • seabird-fisheries interactions
  • Vessel Monitoring Systems (VMS)
  • RESPONSES
  • FISHERIES
  • CATCH
  • TRACKING
  • CONSEQUENCES
  • SEABIRD BYCATCH
  • MORATORIUM
  • IMPACTS
  • REVEALS

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