Occurrence of Lernaeocera branchialis on whiting (Merlangius merlangus) on the Belgian continental plat and the southern North Sea
1992
Declerck, D. (Rijkscentrum voor Landbouwkundig Onderzoek, Oostende (Belgium). Rijksstation voor Zeevisserij)
In the period of 1986-92 the occurrence of the copepod Lernaeocera branchialis in whiting in the Belgian continental plat and the southern North Sea was examined. The infected fish rate was significantly higher in spring than in autumn. A negative correlation with the seawater temperature, y = -0.27 x + 53.7 was found (r = -0.84). On the other hand the rate of copepod infected fish, found in the open sea was smaller than in the Belgian continental plat. This may be explained by the absence of the first intermediate host, 'flounder', during most of the year. Nevertheless the open sea sections are visited by flounder during the spawning period (March and April). With regard to the condition, whiting has been significantly influenced by the presence of the copepod. An increase of weight loss and a decrease of the liver fat content was noted. The presence of Lernaeocera branchialis was also reflected in the blood parameters, i.e. the reduced erythrocyte count, the decrease of haematocrit readings and the lowering of haemoglobin content.
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