Multispecies analysis in Balsfjord, northern Norway: solution and sensitivity analysis of a simple ecosystem model
A simple ecosystem approach to the multispecies analysis of a fjord in northern Norway is given. Species are treated as either species or species groups. Cod are separated into three age groups: 0's. l's. and 2 +. The initial analysis solves a set of biomass equations such that annual biom...
| Published in: | ICES Journal of Marine Science |
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| Main Authors: | , |
| Format: | Text |
| Language: | English |
| Published: |
Oxford University Press
1990
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| Subjects: | |
| Online Access: | http://icesjms.oxfordjournals.org/cgi/content/short/47/2/175 https://doi.org/10.1093/icesjms/47.2.175 |
| Summary: | A simple ecosystem approach to the multispecies analysis of a fjord in northern Norway is given. Species are treated as either species or species groups. Cod are separated into three age groups: 0's. l's. and 2 +. The initial analysis solves a set of biomass equations such that annual biomass production for each group equals total annual losses to fishing and predation. This analysis is then extended to incorporate information from resource surveys of abundance, and a continuum of solutions is possible depending on the degree of confidence placed in the food composition and the survey data. Movement along the continuum is achieved by changing the availability of the groups to predation. A solution was obtained for 1975–1976 data for the fish species. Solution biomasses were generally higher than survey estimates, suggesting undersampling by the survey. Investigations of this static solution using input-output analysis and Monte Carlo sensitivity methods emphasized the dominant influence of cod on the ecosystem, mediated through predation. Primary productivity in Balsfjord was channelled mainly through the pelagic system, although a significant proportion passed through the benthic system, including flatfish. Temperature was found to strongly influence system characteristics through the growth potential of secondary production. |
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