Variations in maturity of haddock in the Barents Sea in relation to year-class strength, age, size, sex and area
Data from the Norwegian Barents Sea bottom trawl surveys in February from 1985 through 1996 are used to analyse variations in haddock (Melanogrammus aeglefinus L.) maturity. Several link functions to estimate maturity ogives are compared. Due to the clustering of samples, both the goodness of fit an...
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| Format: | Text |
| Language: | English |
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1999
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.620.3813 http://journal.nafo.int/J25/korsbrekke.pdf |
| Summary: | Data from the Norwegian Barents Sea bottom trawl surveys in February from 1985 through 1996 are used to analyse variations in haddock (Melanogrammus aeglefinus L.) maturity. Several link functions to estimate maturity ogives are compared. Due to the clustering of samples, both the goodness of fit and various other test statistics are calculated using an effective sampling size lower than the total number of samples. Length and year-class strength are used as continuous explanatory variables while year, age, sex and area are class variables. A strong year effect was detected which appears to be related to the very large 1990 year-class. The year-class strength explains additional variation. That is: when abundance is high, the proportions mature are reduced for otherwise similar haddock (with respect to length, age, sex and area). Both sex and area effects were significant. Males mature at younger ages and shorter lengths than females and there is a tendency for proportions mature to be lower in the eastern part of the Barents Sea. |
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