Journal Article

Short-term stock assessment of <i>Loligo gahi</i> at the Falkland Islands: sequential use of stochastic biomass projection and stock depletion models

Rubén Roa-Ureta and Alexander I. Arkhipkin

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 64, issue 1, pages 3-17
Published in print January 2007 | ISSN: 1054-3139
Published online November 2006 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1093/icesjms/fsl017
Short-term stock assessment of Loligo gahi at the Falkland Islands: sequential use of stochastic biomass projection and stock depletion models

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Roa-Ureta, R. and Arkhipkin, A. I. 2007. Short-term stock assessment of Loligo gahi at the Falkland Islands: sequential use of stochastic biomass projection and stock depletion models – ICES Journal of Marine Science, 64, 3–17.

Two short-term stock assessment models are combined to examine the pre-season, in-season, and post-season dynamics of the Loligo gahi fishery off the Falkland Islands over four consecutive fishing seasons. A stochastic biomass projection model (SBPM) projects a pre-season survey-based biomass estimate from the date of the survey to the start of the season. A stock depletion model (SDM) assesses in-season biomass from commercial daily catch-and-effort data. The SBPM projects the SDM biomass estimate at the end of the season to a post-season date of spawning. Combining the SBPM and the SDM helps to clarify the spatio-temporal functioning of the stock and to assess the comparability of survey- and fishery-based estimates of biomass. For the first 2005 season, projected length frequencies indicate two pulses of recruitment onto the fishing grounds. Survey-based projections of biomass were lower than equivalent fishery-based estimates. Over two surveys, the sex ratio was balanced, suggesting full recruitment of both sexes onto the fishing grounds, and the ratio of survey-projected to fishing-estimated biomass was constant. This constant is interpreted as a scaling factor between survey biomass and absolute biomass.

Keywords: biomass projection model; Falkland Islands; Loligo gahi; stock assessment; stock depletion model

Journal Article.  8964 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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