Maturation characteristics in Norwegian spring-spawning herring before, during, and after a major population collapse
Working paper
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http://hdl.handle.net/11250/100535Utgivelsesdato
2002Metadata
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Sammendrag
The immense Norwegian spring-spawning herring (Clupea harengus) population collapsed to the state
of commercial extinction in the late 1960s, probably largely due to overfishing; the stock has fully
recovered since the 1980s. It is known that the collapse strongly affected maturation characteristics.
However, the long-term patterns of maturation in this stock have remained largely undescribed. Using
discriminant analysis and artificial neural networks, the age at maturation for individual fish can be
predicted fromroutine scalemeasurements.We applied thesemethods to historical data on herring scales
available from 1935 up to the present, in order to (1) describe the long-term variability in both age and
length at50%maturity, and (2) compute new, revisedmaturity ogives for the stock over the same period
with temporal resolution of one year.This new information, with improved temporal resolution, enables
comparisons ofmaturation characteristics before, during, and after the population collapse. As a further
step, in order to increase our understanding of the potential impact of commercial fisheries on the genetic
composition of fish stocks, we aim to disentangle genetic from phenotypic aspects of maturation.
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ICES CM documents2002/Y:10