High-grading and over-quota discarding in mixed fisheries

High-grading and over-quota discarding in mixed fisheries High-grading is the decision by fishers to discard fish of low value that allows them to land more valuable fish. A literature review showed high-grading is reported in commercial and non-commercial fisheries around the world, although the number of observations is small. High-grading occurs in fisheries that are restricted to land their total catch due to management, market or physical constraints. Using the mixed flatfish fishery as a model system, a dynamic state variable model simulation showed that high-grading of certain grades occurs throughout the year when their ex-vessel price is low. High-grading increases with the degree of quota restriction, while the level of over-quota discarding is unrelated to the quota level. The size composition of the high-graded catch differs from the landed catch. Due to the differences in the seasonal variation in size specific ex-vessel price, the effect of quota restrictions on the size composition of the discarded catch is non-linear. High-grading is difficult to detect for the fishery inspection as it occurs on-board during the short period when the catch is processed. We conclude that high-grading is under-reported in fish stocks managed by restrictive quota, undermining the quality of stock assessments and sustainable management of exploited fish stocks. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Reviews in Fish Biology and Fisheries Springer Journals

High-grading and over-quota discarding in mixed fisheries

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Publisher
Springer Journals
Copyright
Copyright © 2015 by The Author(s)
Subject
Life Sciences; Freshwater & Marine Ecology; Zoology
ISSN
0960-3166
eISSN
1573-5184
D.O.I.
10.1007/s11160-015-9403-0
Publisher site
See Article on Publisher Site

Abstract

High-grading is the decision by fishers to discard fish of low value that allows them to land more valuable fish. A literature review showed high-grading is reported in commercial and non-commercial fisheries around the world, although the number of observations is small. High-grading occurs in fisheries that are restricted to land their total catch due to management, market or physical constraints. Using the mixed flatfish fishery as a model system, a dynamic state variable model simulation showed that high-grading of certain grades occurs throughout the year when their ex-vessel price is low. High-grading increases with the degree of quota restriction, while the level of over-quota discarding is unrelated to the quota level. The size composition of the high-graded catch differs from the landed catch. Due to the differences in the seasonal variation in size specific ex-vessel price, the effect of quota restrictions on the size composition of the discarded catch is non-linear. High-grading is difficult to detect for the fishery inspection as it occurs on-board during the short period when the catch is processed. We conclude that high-grading is under-reported in fish stocks managed by restrictive quota, undermining the quality of stock assessments and sustainable management of exploited fish stocks.

Journal

Reviews in Fish Biology and FisheriesSpringer Journals

Published: Oct 27, 2015

References

  • Comprehensive discard reconstruction and abundance estimation using flexible selectivity functions
    Aarts, G; Poos, JJ
  • Comparative evaluation of a mixed-fisheries effort-management system based on the Faroe Islands example
    Baudron, A; Ulrich, C; Nielsen, JR; Boje, J
  • Modelling discard ogives from Irish demersal fisheries
    Borges, L; Zuur, AF; Rogan, E; Officer, R
  • What do pelagic freezer-trawlers discard?
    Borges, L; Keeken, OA; Helmond, ATM; Couperus, B; Dickey-Collas, M
  • How do individual transferable quotas affect marine ecosystems?
    Branch, TA
  • Replacing trip limits with individual transferable quotas: implications for discarding
    Branch, TA; Rutherford, K; Hilborn, R
  • Using inferred drivers of discarding behaviour to evaluate discard mitigation measures
    Catchpole, TL; Feekings, JP; Madsen, N; Palialexis, A; Vassilopoulou, V; Valeiras, J; Garcia, T; Nikolic, N; Rochet, M-J

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