Publication Abstract

Alternative methods for the estimation of immigration to the Icelandic cod stock

J.G. Shepherd and J.G.Pope

Periodic migrations of fish from Greenland are known to have augmented the Icelandic cod stock on many occasions during the last 50 y. These immigrations have been observed both in the catch-at-age compositions, and through tagging experiments. Two new and independent methods for estimating the extent of immigration have been developed, based on analysis of weight-at-age data; comparison of virtual population analyses for a restricted range of ages and the full range of ages in the available data. Both methods confirm recent strong immigration of the 1973 and 1984 year classes, but also suggest that significant immigration was a fairly regular event throughout the 1970s, and also occurred in 1985. It appears that immigration is quite strongly correlated with the year-class strength at Greenland, and that between 20% and 60% of the Greenland fish eventually return to rejoin the Icelandic stock.

Reference:

J.G. Shepherd and J.G.Pope, 1993. Alternative methods for the estimation of immigration to the Icelandic cod stock. Fisheries Oceanography, 2: 254-259.