On the effect on cod and herring ®sheries of retuning the Revised Management Procedure for minke whaling in the greater Barents Sea
In a model with four species ± cod, capelin, herring and minke whales ± the ®sh populations are age and length distributed, while the minke whale is age and sex distributed. The time step is one month, and there are two areas (The Barents Sea and parts of the Norwegian Sea). There is a food-web with...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.515.1534 http://folk.uio.no/tores/Publications_files/Schweder_Hagen_Hatlebakk_FR1998.pdf |
| Summary: | In a model with four species ± cod, capelin, herring and minke whales ± the ®sh populations are age and length distributed, while the minke whale is age and sex distributed. The time step is one month, and there are two areas (The Barents Sea and parts of the Norwegian Sea). There is a food-web with minke whales as top predators, consuming herring, capelin and cod according to a non-linear consumption function in available prey abundance. The consumption function for minke whales is roughly estimated. The opportunistic minke whale may forage on plankton and other ®sh than cod, capelin or herring, and is thus, modelled as having carrying capacity and demographic parameters independent of the status of the ®sh stocks in the model. The ®sh-®sheries are managed by ®xed VPA-based ®shing mortalities (cod and herring) and Captool (capelin), while minke whaling is managed according to the RMP of the IWC. The model is stochastic in ®sh recruitment and in survey indices for minke whales. The model is simulated over 100-year periods in a number of scenarios spanned by nine experimental factors. The core of the experimental design is an orthogonal array with 27 points. The primary study variable is the tuning of the RMP, and the response variables are catches and stock sizes of cod, herring and minke whale. The responses are taken as yearly means over the last 90 years of the period. When the tuning of the RMP is changed from the current level of targeting the ®nal stock at 72 % of carrying capacity to 60%, the annual catch of whales increases with some 300 animals, while the annual catch of cod increases with some 0.1 million ton on the average. For herring, no clear main effect was found on catch |
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