Journal Article

An ecosystem element added to the assessment of Norwegian spring-spawning herring: implementing predation by minke whales

Sigurd Tjelmeland and Ulf Lindstrøm

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 62, issue 2, pages 285-294
Published in print January 2005 | ISSN: 1054-3139
Published online January 2005 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1016/j.icesjms.2004.12.011
An ecosystem element added to the assessment of Norwegian spring-spawning herring: implementing predation by minke whales

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Predation by minke whales is incorporated in the assessment model of the Norwegian spring-spawning herring stock (SeaStar) used by the ICES Working Group. Three assessment scenarios are performed and evaluated: (1) Default historic assessment where the natural mortality (M) is fixed, (2) assessment where natural mortality is estimated both for adult and juvenile herring, (3) assessment where consumption by minke whales is modelled and the predation and residual natural mortalities are estimated. The annual consumption of juvenile herring in the Barents Sea is estimated exogenously using diet data and a bioenergetic model. The estimated consumption is included in the objective function and the parameters determining the modelled consumption are estimated together with other free parameters of the model in a single operation. The estimated total natural mortality of juvenile herring is lower than the value assumed by the working group (M = 0.9) when either minke whales are included in the model (M = 0.49) or the parameter is estimated directly (M = 0.48). Assessment 3 generates 19% and 34% lower adult and juvenile stock sizes, respectively, than assessment 1, whereas assessments 2 and 3 generate relatively similar stock size estimates. The predation mortality constituted 45% and 10% of the total natural mortality of adult (M = 0.15) and juvenile herring (M = 0.49), respectively.

Keywords: assessment; herring; minke whales; northeast Atlantic; predation

Journal Article.  6118 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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