Predation by cod (Gadus morhua) on capelin (Mallotus villosus) in the Barents Sea: implications for capelin stock assessment

The Barents Sea capelin (Mallotus villosus) is the most important prey item for the stock of Northeast Arctic cod (Gadus morhua) in the Barents Sea, a nd cod is also the most important predator on capelin in this area. Mainly cod larger than 25 cm consume capelin. The Barents Sea capelin stock is ass essed using a multispecies assessment method. involving in addition to cape lin and cod, the stock of Norwegian spring-spawning herring (Clupea harengu s). One fundamental assumption in this method is that in the period January -April, only immature cod prey on only mature capelin. In this paper, it is found that immature capelin makes up a significant part of the consumption of capelin by cod during the period January-April. Also, mature cod to som e extent take part in the consumption of capelin during this period. These findings are both in contrast to what is currently assumed in capelin asses sment. The results indicate that the assessment method presently in use ove restimates the consumption of mature capelin by cod in this period. (C) 200 1 Elsevier Science B.V. All rights reserved.