SUMMARY
Brazilian longliners have been fishing in the west of the South Atlantic Ocean since 1956. The Task II ICCAT dataset contain information about the Brazilian national and leased boats. Swordfish is the target for some fishermen, like those of the national fleet, while others have been aiming for tuna...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.509.3613 http://www.iccat.int/Documents/CVSP/CV060_2007/no_2/CV060020471.pdf |
| Summary: | Brazilian longliners have been fishing in the west of the South Atlantic Ocean since 1956. The Task II ICCAT dataset contain information about the Brazilian national and leased boats. Swordfish is the target for some fishermen, like those of the national fleet, while others have been aiming for tunas, mainly albacore and bigeye. In this paper delta-lognormal models and Brazilian Task II dataset were used to estimate relative abundance of albacore. In the first approach the fleets were pooled according to the species they were targeting, while in the second only the data of fleets that aimed for albacore were analyzed. In the delta-lognormal framework it was assumed that the proportion of positive catches follows a binomial distribution, while the author assumed log-normal distributions when modeling the positive catch rates. The “year ” effects in the binomial and in log-normal models were estimated, by which indexes of abundance were based. Standard errors of the abundance indexes estimated using information only concerning fleets that target albacore, were smaller than those gathered when all the information was analyzed. Furthermore the two sets of estimations have shown different time trends. |
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