Return of Norwegian spring spawning herring (Clupea harengus L.) to historical spawning grounds off southwestern Norway
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From the mid-1940s to mid-1960s a northward displacement of the spawning areas of the Norwegian Spring Spawning Herring was observed. Further retraction of the population from traditional feeding and spawning grounds occurred as the stock collapsed in the late 1960s. The spawning grounds off southwestern Norway were abandoned after 1959. Ever since, spawning appears to have been restricted to a few coastal grounds and offshore banks off mid-Norway, primarily off the Møre district. At present, the abundance of the spawning stock remains comparatively low; 1.5-2 mill. tonnes as compared with 7-10 mill. tonnes in the 1950s. However, in the spawning seasons from 1989 onwards, spring spawners have again been observed at the southwestern grounds. The herring at these southern grounds in 1990 and 1991 were Norwegian Spring Spawners and utilized traditional spawning sites. The spawning time was about a month later than in the 1930s but similar to that in the 1950s. Results of acoustic surveys showed that of the total spawning stock, 1.5 - 2 % used the southwestern grounds i 1990 and 1991.