Abstract
We investigate how cod feeding data may be included into a recently developed age-structured model for a coastal cod population in a small fjord in northern Norway. The model integrates data from mark-recapture experiments, trawl-surveys and commercial catches. The fjord population has high biomass density (2-3 tonnes km-2) and low fishing mortality rates (F
Highlights
Coastal cod is a dominant predator and an important commercial species in the fjords and coastal waters in northern Norway (Bax and Eliassen, Sea and using the Norwegian coast as their spawning area (Jakobsen 1987)
In the case of the feeding data, which is the key concern of this paper, we investigated the effects of giving very low weight
The results from the sensitivity analysis indicate that the integration of the feeding data into the model did not cause any loss in robustness of the model (Tables 3 and 4) since most changes in estimates were relatively small
Summary
Coastal cod is a dominant predator and an important commercial species in the fjords and coastal waters in northern Norway (Bax and Eliassen, Sea and using the Norwegian coast as their spawning area (Jakobsen 1987). In the course of this, the area has intensively been sampled by trawl and extensive tagging experiments of wild and released cod have been performed (Nøstvik and Pedersen, 1999a, b). Subm.) uses data from mark-recapture experiments together with data on the numbers at age caught in trawl surveys and by the commercial fishery for a seven-year period (1989-1996). Tagging results indicate that there is a minor migratory exchange of cod between Sørfjord and other areas, and there are no indications of seasonal The existing model utilises the data sets to produce estimates of abundance and mortality of fish older than two years of age, but in this paper we use data on cod feeding to expand the model to estimate abundance and mortality rates for the 0-1 age groups.
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