Journal Article

The estimation of hidden seal-inflicted losses in the Baltic Sea set-trap salmon fisheries

Arne Fjälling

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 62, issue 8, pages 1630-1635
Published in print January 2005 | ISSN: 1054-3139
Published online January 2005 | e-ISSN: 1095-9289 | DOI:
The estimation of hidden seal-inflicted losses in the Baltic Sea set-trap salmon fisheries

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  • Environmental Science
  • Marine and Estuarine Biology


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A database has been constructed using detailed information on catches and seal-disturbance from contracted commercial fishers in the northern Baltic Sea. A model was developed for the calculation of seal-induced losses in set traps for salmon. The model compared catches on consecutive days or day-pairs. It was found that the total losses in set traps were high: 61% of the potential catch in a trend-adjusted sample of paired data. A significant part of these losses, such as fish wholly removed from gear was hidden. The traditional method of assessing losses by counting the remains of fish underestimated losses by 46%. The scaring effect of seal visits was not included. The model was also used for an analysis of the damage process. There were significant negative after-effects of seal visits on catch levels. It was also found that seal visits co-occur with salmon runs. It seems that seals prefer smaller to larger salmon when raiding traps. It is suggested that the traditional method of estimating losses by counting fish remains should be calibrated when used and that the new model with day-pairs should be tried in analyses of seal interference in other fishing operations.

Keywords: conflict; damage; fishery; grey seal; hidden loss; predation; salmon

Journal Article.  3710 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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