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Capelin (Mallotus villosus) is a short-lived, coldwater, pelagic species that occurs in large populations in the Barents Sea, around Iceland and in the Newfoundland–Labrador area in the North Atlantic. Most individuals spawn only once at age three or four and die shortly after spawning. The commercial fisheries for capelin in the three areas are prosecuted on the pre-spawning and spawning age groups and knowledge of recruitment to the spawning stock and factors affecting recruitment are important in the management of the fisheries. Herein, we review the state of knowledge regarding recruitment in the three areas and factors that affect recruitment. Year class strength of capelin is fixed fairly early in life; at 0-group stage in the Barents Sea, by age 1 or earlier for Icelandic capelin, and within 2 weeks of hatching for the beach spawners in the Newfoundland area. No obvious single factor, common to the three stocks, has been proven to exert a significant influence on recruitment. In the Barents Sea, juvenile herring prey heavily on capelin larvae and when the estimates of the abundance of these juvenile herring were accounted for in the capelin stock–recruitment analysis, the fit in the stock–recruitment relationship improved. In Iceland, there is no reason to implicate predation as a dominant factor, although detailed studies have not been carried out. In the Newfoundland and Labrador area earlier studies suggested two factors were important for recruitment success: the frequency of onshore winds at a critical period during the residence of newly hatched larvae in the beach gravel and the presence of warm waters during the early larval phase in the pelagic environment. With further testing using more data, the temperature factor was found not to be significant but the frequency of onshore winds still explained a significant portion of the variation in year class strength. There appears to be no significant biological influence, such as predation, that has influenced recruitment in this area. |
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