Does size really matter? Effects of fish surface area on the settlement and initial survival ofLepeophtheirus salmonis, an ectoparasite ofAtlantic salmon Salmo salar

[摘要] ABSTRACT: The effect of the size of the surface area of a fish host on settlement and initial survival of Lepeophtheirus salmonis (Krøyer, 1837) was determined. Atlantic salmon Salmo salar L. of various sizes‹small (43 ± 4 g), medium (173 ±32 g) and large (644 ± 62 g)‹were initially examined to ascertain their respective body surface area, excluding gill surface. The initial examination showed a size-dependent body to fin area ratio, with the fin area of small fish representing 34% of thetotal body area and the fin area of medium and large fish representing 26 and 23%, respectively. Regression analysis of the body weight and standard length against total body surface area gave a good correlation and high R² values. Twosimultaneous experimental infections with approximately 7000 copepodids of L. salmonis were carried out on fish populations of mixed sizes consisting of 30 small fish, 10 medium-sized fish and 5 large fish, with an approximate total surface areaper size group of 2700 cm². Higher numbers of parasites were found on the small size group, which also had the highest parasite density, with 0.25 and 0.45 parasites cm^-2. Comparison of samples of 5 fish per experimental grouprevealed that the larger fish had the highest mean numbers of parasites, but the smaller fish still retained the highest density. There was a statistically significantly higher settlement on the fins than on the remainder of the body surface in all sizegroups. Highest numbers of parasites were particularly found on the dorsal and pectoral fins. Examination of the surface surface area revealed that the dorsal fin had the greater parasite density, with >2 parasites cm^-2 in all fish sizegroups. These data provide insight into the effects of the amount of host surface area available on parasite settlement and survival, and highlight the potentially increased susceptibility of farmed salmon smolts to infection of this ectoparasite.

[学科分类] 生物科学（综合）

[关键词] Lepeophtheirus salmonis;Sea lice;Surface area;Settlement