Selective Exploitation of Capelin (Mallotus villosus) Eggs by Winter Flounder (Pseudopleuronectes americanus): Capelin Egg Mortality Rates, and Contribution of Egg Energy to the Annual Growth of Flounder

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Abstract
The consequences of winter flounder (P. americanus) predation on capelin (M. villosus) eggs, in both terms of the egg mortality and the contribution of energy ingested to the annual growth of flounder, were investigated at Bryant''s Cove, Conception Bay, Newfoundland [Canada]. Flounder density in the nearshore area adjacent to the capelin spawning beach increased sharply in each of the 3 study years in response to the presence of spawning capelin and to the density of capelin eggs on the spawning beaches. Capelin eggs were the dominant item in the diet of winter flounder 14-34 cm TL [total length], averaging 59% by weight. Flounder .gtoreq. 35 cm TL fed less heavily on capelin eggs (22% of food consumed by weight) but because of their larger size and ration were an important source of predation. Egg mortality due to flounder predation was estimated to average 5.0, 2.2 and 1.9% in 1978, 1979 and 1980, respectively. Egg mortality due to predation is believed to be significantly greater at deepwater demersal spawning sites and may have a significant impact on recruitment in demersal spawners. The average energy gain to winter flounder resulting from consumption of capelin eggs was estimated to contribute 23% of the annual growth of flounder in the region (approximate 95% confidence interval: 10-40%). Selective exploitation of capelin eggs by postspawning flounder may also contribute significantly to the rapid recovery of body condition following the extensive depletion of tissue resources due to winter fasting, gonad production and spawning.

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