Search

The collapse of marine fisheries worldwide has forced recognition of the fact that sustainable fisheries management cannot be achieved without a reasonable understanding of stock structure. Fisheries focusing on species that exhibit seasonal migrations between spawning and feeding grounds should consider the composition of feeding aggregations of presumed mixed origin. Using nine microsatellites and the Pan I locus, we assess the contribution of two previously described major spawning components of Icelandic cod Gadus morhua (southwest and northeast) to two large feeding and two large juvenile aggregations of presumed mixed origin and situated in the northwest and northeast of Iceland. The Bayesian approaches (STRUCTURE and BAYES) revealed that, with the exception of the juvenile samples collected in 2002 and 2003 in the northeast, most of the individuals originated from the southwest. These results confirmed that the Icelandic cod exhibit a complex biological pattern involving spawning site fidelity and migration to and from feeding aggregations. The sustainable management of the Icelandic cod is likely to be compromised if its complex dynamics is not properly integrated into fisheries management plans. [ABSTRACT FROM AUTHOR]

Óskarsson, G. J., Gudmundsdottir, A., and Sigurdsson, T. 2009. Variation in spatial distribution and migration of Icelandic summer-spawning herring. – ICES Journal of Marine Science, 66: 1762–1767.The distribution of the fishable stock of Icelandic summer-spawning herring (Clupea harengus L.) and the overwintering grounds have changed with fishing seasons from 1978/1979 through 2006/2007. The possible causes investigated include variation in sea temperatures, stock size, and annual recruitment. The stock collapsed as a result of overfishing and environmental changes during the late 1960s, since when the spawning stock has gradually increased, from 11 kt in 1972 to 800 kt in 2006. These changes coincided with geographic variation in its distribution. We identify five phases, based on a graphic analysis and the centre of gravity of the fishery. Investigations on a large geographic scale gave no clear indication that sea temperature has affected the distribution. Changes were also not clearly related to stock size or year-class strength. The distribution change in the late 1990s may be partly explained by year classes adopting a new migration pattern when entering the fishable stock. [ABSTRACT FROM PUBLISHER]