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

Sherley, R. B. et al. (2018) Bayesian inference reveals positive but subtle effects of experimental fishery closures on marine predator demographics. Proceedings of the Royal Society of London Series B: Biological Sciences, 285(1871), 20172443. (doi: 10.1098/rspb.2017.2443) (PMID:29343602) (PMCID:PMC5805942)

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 forage-fish-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.

• Item Type: Articles
• Additional Information: This work was funded by the Earthwatch Institute; Bristol Zoological Society; Leiden Conservation Foundation; Mohamed bin Zayed Species Conservation Fund; Riverbanks Zoo and Garden Conservation Support Fund; the Charl van der Merwe Trust, through BirdLife South Africa’s African penguin species champion project; a Department of Science and Technology Centre of Excellence grant to the FitzPatrick Institute of African Ornithology; the South African Research Chairs Initiative, funded through the DST and administered by the National Research Foundation; and the Natural Environment Research Council (grant no. NE/G001014/1).
• Keywords: African penguin, Benguela ecosystem, fishing closures, forage fish, marine protected areas, seabird–fisheries interactions.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Horswill, Dr Catharine
• Authors: 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., and Votier, S. C.
• College/School: College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
• Journal Name: Proceedings of the Royal Society of London Series B: Biological Sciences
• Publisher: The Royal Society
• ISSN: 0962-8452
• ISSN (Online): 1471-2954
• Published Online: 17 January 2018
• Copyright Holders: Copyright © 2018 The Authors
• First Published: First published in Proceedings of the Royal Society of London Series B: Biological Sciences 285(1871): 20172443
• Publisher Policy: Reproduced under a Creative Commons License
• Data DOI: 10.5061/dryad.d4977