Observations on the embryonic development of capelin (Mallotus villosus MÜLLER) from the Barent Sea

The embryonic development of the Barents Sea capelin is described, with emphasis of characteristic features which can be applied in the ageing of eggs. The development is described for three different temperatures observed on the spawning grounds off the coast of Finnmark. The larval size at hatching, the ability of the eggs to adhere to the substratum, and the fertilization rate at different salinities are also discussed

Growth of the Barents Sea capelin (Mallotus villosus) in relation to climate

The history of capelin assessment in the Barents Sea has shown that the growth of individual capelin has varied between years and different parts of the capelin distribution area. As the number of individuals in this stock is very high, even small changes in individual growth will affect the surplus production and the catches which may be taken from it. If this growth could be estimated in advance, the assessment could be made more precise. Temperature variation has been suggested as a factor which could be partly responsible for the variation in growth. To study this possibility, we compared corresponding values of temperature and length increment of the capelin in different parts of the Barents Sea from 1976 to 1985. The mean temperature in subareas was calculated by averaging the temperatures for the depth interval 10-200 m at all of the hydrographical stations taken each September in each statistical square which the sea is devided, and then combining the squares to form subareas. The estimates of growth were calculated by substracting the backcalculated length corresponding to the outermost winter ring in the otolith from the length at sampling. A positive covariance between water temperature and growth was indicated when all the material was considered, but no clear correspondance was found between temperature and growth within subareas

Pelagic Fish and the Ecological Impact of the Modern Fishing Industry in the Barents Sea

The Barents Sea/Norwegian Sea ecosystem is inhabited by two large pelagic fish stocks, the Norwegian spring spawning herring and the Barents Sea capelin. The herring stock feeds in the high-production polar front area in the western Norwegian Sea, and spawns at the Norwegian coast. The larvae are transported into the Barents Sea, where they spend the first two to four years of life. The capelin stock spends its whole life in the Barents Sea, spawning along the southern coasts and feeding in the nutrient-rich areas in the northern parts of the sea. The herring stock was brought almost to extinction during the 1960s by the combined effect of overfishing and environmental conditions. This stock is now recovering. Much fishing effort was shifted to capelin when the herring fishery was stopped, and the capelin supported large fisheries in the 1970s. In the mid 1980s, the capelin stock size suddenly declined to a very low level. The factors involved were recruitment failure, low individual growth rates, high natural mortality, and, in the last phase, high fishing mortality. The recruitment failure was most likely caused by predation by some abundant year classes of herring in 1983-85. The low growth rate was probably caused by the scarcity of prey organisms, while the high mortality rate of the adult capelin stock was an effect of predation from abundant year classes of cod during the same period. After having recovered in the period 1989-91, the capelin stock once more collapsed during 1992-93. The reasons were the same as for the collapse in the 1980s, except that fishing had no effect on the most recent collapse.Key words: Barents Sea, ecology, fisheries, capelin, herring, polar codL'écosystème formé par la mer de Barents et la mer de Norvège est peuplé par deux importants stocks de poissons pélagiques, le hareng norvégien qui se reproduit au printemps et le capelan de la mer de Barents. Le stock de hareng se nourrit dans la zone hautement productive du front polaire dans l'ouest de la mer de Norvège, et fraie sur la côte norvégienne. Les larves sont transportées dans la mer de Barents, où elles passent de deux à quatre ans au début de leur vie. Le stock de capelan passe toute sa vie dans la mer de Barents, frayant le long des côtes méridionales et se nourrissant dans les zones riches en éléments nutritifs situées dans les parties septentrionales de la mer. Au cours des années 1960, le stock de hareng a presque été décimé en raison de l'effet combiné de la surpêche et des conditions environnementales. Ce stock est maintenant en train de se renouveler. Lorsqu'on a cessé de pêcher le hareng, la pêche au capelan a connu un essor considérable et, dans les années 70, ce poisson a soutenu une importante industrie de pêche. Au milieu des années 80, la taille du stock de capelan a décliné subitement pour atteindre un très bas niveau. Les facteurs en cause étaient le manque de renouvellement, un faible taux de croissance individuelle, une mortalité naturelle élevée, et, durant la dernière phase, une haute mortalité due à la pêche. Le manque de renouvellement était probablement dû à la prédation exercée par certaines classes abondantes de harengs de 83 à 85. Le faible taux de croissance était probablement dû à la rareté des organismes-proies, tandis que le taux élevé de mortalité du stock de capelan adulte était une conséquence de la prédation causée par d'abondantes classes annuelles de morues durant cette même période. Après avoir récupéré entre 1989 et 1991, le stock de capelan s'est de nouveau effondré au cours des années 92-93. Les raisons en étaient les mêmes que celles de l'effondrement des années 1980, sauf que la pêche n'était pas un facteur en cause.Mots clés: mer de Barents, écologie, pêcheries, capelan, hareng, morue polair

Report on the otolith workshop held at the Soviet/Norwegian symposium on the Barents Sea capelin, Bergen, Norway 14-19 August 1984

The proceedings of the Soviet-Norwegian symposium on the Barents Sea capelin. Bergen, 14-19 August 1984

A logistic function to track time-dependent fish population dynamics

publishedVersio

Multispecies considerations

Working document to the ICES Arctic Fisheries Working Group, Copenhagen 20-28 August 199