Targeted demersal fish species exhibit variable re

Authors: Katrina R Bornt Dianne L McLean Tim J Langlois Euan S Harvey Lynda M Bellchambers Scott N Evans Stephen J Newman

Publish Date: 2015/08/08

Volume: 34, Issue: 4, Pages: 1297-1312

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Abstract

Natural fluctuations in the abundance and length of targeted fish are often disrupted by acute environmental changes and anthropogenic impacts particularly fishing pressure Longterm assessments of targeted fish populations inside and outside areas closed to fishing are often necessary to elucidate these effects yet few of these studies extend over long time periods We assessed trends in the abundance and length of six targeted fish species in areas open and closed to fishing on seven occasions spanning a 9year period 2005–2010 and 2013 at the Houtman Abrolhos Islands Western Australia Shallow 8–12 m and deep 22–26 m coraldominated reef sites were sampled across four geographically separated island groups using baited remote underwater stereovideo stereoBRUV Between 2005 and 2010 populations of Lethrinus miniatus Lethrinus nebulosus Plectropomus leopardus and Chrysophrys auratus became increasingly dominated by larger individuals potentially indicative of an ageing population Between 2010 and 2013 however there was a significant increase in the proportion of smaller L miniatus L nebulosus and P leopardus in both open and closed areas reflecting increased recruitment perhaps due to changing environmental conditions associated with a marine heat wave anomaly This recruitment pulse was not observed for the other species in this study Chr auratus Choerodon rubescens and Glaucosoma hebraicum Lethrinus miniatus L nebulosus Chr auratus and P leopardus were larger in closed areas relative to open areas however they were not more abundant These complex responses to protection also varied across sampling years for certain species eg P leopardus Monitoring changes over the longterm in areas open and closed to fishing provides a sound basis for separating environmental variability from that associated with fishing mortality which is crucial for optimising fisheries managementLogistical support was provided by The University of Western Australia and the Department of Fisheries WA We are appreciative of the assistance of Laura Fullwood Ben Doncon Rebecca Thomas Nick Konzewitsch and Josh Dornan with fieldwork and we are indebted to Todd Bond Matthew Birt Laura Fullwood and Damon Driessen for support with video analysis We also thank the Department of Fisheries WA staff for assisting in the revision of manuscript drafts This work was undertaken with UWA Animal Ethics approval RA/3/100/1204

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