Bayesian inference reveals positive but subtle effects of experimental fishery closures on marine predator demographics

Richard B. Sherley, Barbara J. Barham, Peter J. Barham, Kate J. Campbell, Robert J. M. Crawford, Jennifer Grigg, Cat Horswill, Alistair McInnes, Taryn L. Morris, Lorien Pichegru, Antje Steinfurth, Florian Weller, Henning Winker, Stephen C. Votier

Research output: Contribution to journalArticle

Abstract

Global forage-fish landings are increasing, with potentially grave consequences for marine ecosystems. Predators of forage fish may be influenced by this harvest, but the nature of these effects is contentious. Experimental fishery manipulations offer the best solution to quantify population-level impacts, but are rare. We used Bayesian inference to examine changes in chick survival, body condition and population growth rate of endangered African penguins Spheniscus demersus in response to 8 years of alternating time-area closures around two pairs of colonies. Our results demonstrate that fishing closures improved chick survival and condition, after controlling for changing prey availability. However, this effect was inconsistent across sites and years, highlighting the difficultly of assessing management interventions in marine ecosystems. Nevertheless, modelled increases in population growth rates exceeded 1% at one colony; i.e. the threshold considered biologically meaningful by fisheries management in South Africa. Fishing closures evidently can improve the population trend of a foragefish-dependent predator-we therefore recommend they continue in South Africa and support their application elsewhere. However, detecting demographic gains for mobile marine predators from small no-take zones requires experimental time frames and scales that will often exceed those desired by decision makers.

Original languageEnglish
Article number20172443
JournalProceedings of the Royal Society B: Biological Sciences
Volume285
Issue number1871
Early online date17 Jan 2018
DOIs
Publication statusPublished - 31 Jan 2018

Keywords

  • African penguin
  • Benguela ecosystem
  • Fishing closures
  • Forage fish
  • Marine protected areas
  • Seabird-fisheries interactions

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)
  • Environmental Science(all)
  • Agricultural and Biological Sciences(all)

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    Sherley, R. B., Barham, B. J., Barham, P. J., Campbell, K. J., Crawford, R. J. M., Grigg, J., Horswill, C., McInnes, A., Morris, T. L., Pichegru, L., Steinfurth, A., Weller, F., Winker, H., & Votier, S. C. (2018). Bayesian inference reveals positive but subtle effects of experimental fishery closures on marine predator demographics. Proceedings of the Royal Society B: Biological Sciences, 285(1871), [20172443]. https://doi.org/10.1098/rspb.2017.2443