Laboratory Studies of Predation by Euphausiid Shrimps on Fish Larvae

Abstract

Despite a large literature on the vulnerability of marine fish larvae to changes in their physical and biotic environment, there is surprisingly little quantitative data available on organisms that eat fish larvae. There is ample evidence that huge mortalities of yolk-sac fish larvae occur (Ahlstrom, 1965); this is not due to lack of food, a factor implicated in the mortality of older larvae (Blaxter, 1969). Predation on yolk-sac larvae may be the most important cause of mortality during the early period in the life history of pelagic fish. There are a number of observations of zooplankters feeding on fish larvae (Garstang, 1900; Lebour, 1925; Wickstead, 1965; Petipa, 1965; Fraser, 1969); copepods, chaetognaths, ctenophores, and a variety of coelenterates have been seen to capture and ingest marine fish larvae. Recently Lillelund and Lasker (1971) quantified the predatorprey relationship between several species of marine copepods and larvae of the northern anchovy, Engvaulis mordax, and described the behavioural responses involved in this interaction. They found, for example, that a variety of marine copepods (but particularly surface-dwelling pontellids) can capture and ingest or fatally injure young anchovy larvae under laboratory conditions.