Is reduced body growth of cod exposed to the gill parasite Lernaeocera branchialis a cost of resistance?
Abstract:Three hundred and sixty-nine cod Gadus morhua were individually marked and caged for 19 months. During this period, each cod was inspected several times for Lernaeocera branchialis. Growth in four groups of cod, identified by their infection history, were compared. During the caging, 79% of the cod remained uninfected, 8·5% were infected, but lost the parasite, 8% were infected with one parasite and 4·5% were infected with more than one parasite. The infected fish either harboured the parasite at caging or were infected during the study period. The highest rate of increase, both in body mass and in standard length (LS), was recorded in the group of male fish infected with one parasite throughout the experimental period. Conversely, those males free from infection showed significantly lower growth. The observed differences in growth could not be explained by changes in variables related to reproductive strategies. The alternative explanation for these results is that resistance to L. branchialis was associated with costs in terms of reduced growth of body mass and LS.
Document Type: Regular Paper
Publication date: 2006-11-01