Estimating whole-lake fish catch per unit effort

Alexander, Timothy; Vonlanthen, Pascal; Periat, Guy; Degiorgi, F.; Raymond, J.C.; Seehausen, Ole (2015). Estimating whole-lake fish catch per unit effort. Fisheries Research, 172, pp. 287-302. Elsevier 10.1016/j.fishres.2015.07.024

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The European standard for gillnetsampling to characterize lake fish communities stratifies sampling effort (i.e., number of nets) within depth strata. Nets to sample benthic habitats are randomly distributed throughout the lake within each depth strata. Pelagic nets are also stratified by depth, but are set only at the deepest point of the lake. Multiple authors have suggested that this design under-represents pelagic habitats, resulting in estimates of whole-lake CPUE and community composition which are disproportionately influenced by ecological conditions of littoral and benthic habitats. To address this issue, researchers have proposed estimating whole-lake CPUE by weighting the catch rate in each depth-compartment by the proportion of the volume of the lake contributed by the compartment. Our study aimed to assess the effectiveness of volume-weighting by applying it to fish communities sampled according to the European standard (CEN), and by a second whole-lake gillnetting protocol (VERT), which prescribes additional fishing effort in pelagic habitats. We assume that convergence between the protocols indicates that volume-weighting provides a more accurate estimate of whole-lake catch rate and community composition. Our results indicate that volume-weighting improves agreement between the protocols for whole-lake total CPUE, estimated proportion of perch and roach and the overall fish community composition. Discrepancies between the protocols remaining after volume-weighting maybe because sampling under the CEN protocol overlooks horizontal variation in pelagic fish communities. Analyses based on multiple pelagic-set VERT nets identified gradients in the density and biomass of pelagic fish communities in almost half the lakes that corresponded with the depth of water at net-setting location and distance along the length of a lake. Additional CEN pelagic sampling effort allocated across water depths and distributed throughout the lake would therefore help to reconcile differences between the sampling protocols and, in combination with volume-weighting, converge on a more accurate estimate of whole-lake fish communities.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Department of Biology > Institute of Ecology and Evolution (IEE) > Aquatic Ecology
08 Faculty of Science > Department of Biology > Institute of Ecology and Evolution (IEE)

UniBE Contributor:

Alexander, Timothy; Vonlanthen, Pascal; Periat, Guy and Seehausen, Ole

Subjects:

500 Science > 570 Life sciences; biology

ISSN:

0165-7836

Publisher:

Elsevier

Language:

English

Submitter:

Marcel Häsler

Date Deposited:

14 Dec 2015 08:32

Last Modified:

11 Sep 2017 07:38

Publisher DOI:

10.1016/j.fishres.2015.07.024

BORIS DOI:

10.7892/boris.73617

URI:

https://boris.unibe.ch/id/eprint/73617

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