Similarities between line fishing and baited stereo-video estimations of length-frequency: novel application of kernel density estimates

Authors

Timothy J. Langlois, The University of Western Australia
Benjamin R. Fitzpatrick, The University of Western Australia
David V. Fairclough, Department of Fisheries, WAFollow
Corey B. Wakefield, Department of Fisheries, WAFollow
Sybrand Alexander Hesp, Department of Fisheries, WAFollow
Dianne L. McLean, The University of Western Australia
Euan S. Harvey, The University of Western Australia
Jessica J. Meeuwig, The University of Western Australia

Document Type

Article

Publication Date

11-29-2012

Journal Title

PLoS One

ISSN

1932-6203

Keywords

Probability density; ignal bandwidth; Fish biology; Fisheries; Islands ; Spawning ;Statistical data ; Statistical distributions

Disciplines

Aquaculture and Fisheries | Marine Biology

Abstract

Age structure data is essential for single species stock assessments but length-frequency data can provide complementary information. In south-western Australia, the majority of these data for exploited species are derived from line caught fish. However, baited remote underwater stereo-video systems (stereo-BRUVS) surveys have also been found to provide accurate length measurements. Given that line fishing tends to be biased towards larger fish, we predicted that, stereo-BRUVS would yield length-frequency data with a smaller mean length and skewed towards smaller fish than that collected by fisheries-independent line fishing. To assess the biases and selectivity of stereo-BRUVS and line fishing we compared the length-frequencies obtained for three commonly fished species, using a novel application of the Kernel Density Estimate (KDE) method and the established Kolmogorov–Smirnov (KS) test. The shape of the length-frequency distribution obtained for the labrid Choerodon rubescens by stereo-BRUVS and line fishing did not differ significantly, but, as predicted, the mean length estimated from stereo-BRUVS was 17% smaller. Contrary to our predictions, the mean length and shape of the length-frequency distribution for the epinephelid Epinephelides armatus did not differ significantly between line fishing and stereo-BRUVS. For the sparid Pagrus auratus, the length frequency distribution derived from the stereo-BRUVS method was bi-modal, while that from line fishing was uni-modal. However, the location of the first modal length class for P. auratus observed by each sampling method was similar. No differences were found between the results of the KS and KDE tests, however, KDE provided a data-driven method for approximating length-frequency data to a probability function and a useful way of describing and testing any differences between length-frequency samples. This study found the overall size selectivity of line fishing and stereo-BRUVS were unexpectedly similar.

Recommended Citation

Langlois, T J, Fitzpatrick, B R, Fairclough, D V, Wakefield, C B, Hesp, S A, McLean, D L, Harvey, E S, and Meeuwig, J J. (2012), Similarities between line fishing and baited stereo-video estimations of length-frequency: novel application of kernel density estimates. PLoS One, 7 (11).
https://library.dpird.wa.gov.au/fr_fja/183