Cessation of the Norwegian drift net fishery: changes observed in Norwegian and Russian populations of Atlantic salmon

Abstract

Jensen, A. J., Zubchenko, A. V., Heggberget, T. G., Hvidsten, N. A., Johnsen, B. O., Kuzmin, O., Loenko, A. A., Lund, R. A., Martynov, V. G., Naesje, T. F., Sharov, A. F., and Okland, F. 1999. Cessation of the Norwegian drift net fishery: changes observed in Norwegian and Russian populations of Atlantic salmon. ‐ ICES Journal of Marine Science, 56: 84‐95. The aim of this study was to evaluate eVects of the ban on the Norwegian coastal drift net fishery in 1989 on the spawning run of Atlantic salmon (Salmo salar) populations in four Norwegian and four Russian rivers. Catches/escapements, size distribution, sea-age proportions, and mean weights of diVerent sea-age groups were collected from oYcial catch statistics and analyses of scale samples. In three of the Norwegian rivers, catches of grilse (1SW) increased significantly after the ban on the drift net fishery. No changes were recorded for multi-sea-winter (MSW) fish. In addition, the proportion of grilse increased in all the Norwegian rivers, and 2SW salmon increased in three of them. The mean weight of grilse increased in all four Norwegian rivers, whereas the mean weight of 2SW fish decreased in the two rivers in southern Norway. The size of 3SW fish did not change. These changes correspond well to actual net selection curves and reported mean weight of drift net catches in diVerent parts of Norway. Trends in the Russian populations were more varying. In the three rivers draining to the Barents Sea, changes were similar to those in the Norwegian rivers. However, these changes were less obvious than those observed in Norwegian populations. The authors conclude that the ban of the drift net fishery significantly aVected the structure of the spawning run in Norwegian Atlantic salmon populations. Furthermore, the results indicate that the drift net fishery aVected Russian salmon populations in rivers draining to the Barents Sea to a lesser extent than Norwegian salmon, and had no eVect in rivers draining to the White Sea.