Journal article

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


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Publication Details

Author list: Sherley RB, Barham BJ, Barham PJ, Campbell KJ, Crawford RJM, Grigg J, Horswill C, McInnes A, Morris TL, Pichegru L, Steinfurth A, Weller F, Winker H, Votier SC

Publisher: Royal Society, The

Publication year: 2018

Journal: Proceedings of the Royal Society B: Biological Sciences

Volume number: 285

Start page: 1

End page: 9

Total number of pages: 9

ISSN: 0962-8452

eISSN: 1471-2954


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.


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Last updated on 2019-18-04 at 09:40