The study presented here is part of a greater project dealingwith recruitment studies of a local herring stock in Lindåspollenenorth of Bergen.Fish predators on herring spawn, mainly cod and haddock, weretrapped in entangling nets near the spawning ground during 1978,1979 and 1980. On the basis of stomach contents of these fishspecies, one has tried to estimate to which degree fish predationon herring spawn influences total egg mortality. During yearswith moderate and heavy spawning, fish feeding on herring eggsseems to play a minor role in Lindåspollene, but during yearswith ligh spawn (1978), fish predation was estimated to make upmaximum 40-60% of total egg number. These estimates dependclosely on fish abundance which is insufficiently known. On thebasis of mean stomach contents and values obtained from theliterature on food consumption and daily energy requirements,a cod specimen has been calculated to ingest about 15-20 000 eggsdaily.Staging of herring eggs in fish stomachs indicates that thenatural mortality of herring eggs is variable, and increasestowards the time of hatching.In situ observations of planktonic invertebrates preyingon newly hatched herring larvae, confirm the presumably highpredator potential of planktonic invertebrates previouslyreported (FOSSUM and JOHANNESSEN 1979). Bolinopsis sp. andSarsia sp. especially, but also Pleurobrachia sp. and other medusae-species were recorded in situ preying on herring larvae.
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出版者
ICES
语言
英语
类型
Working Paper
来源
Johannessen, Arne12 s.
团体作者
Johannessen, Arne
2013-06-15
AGRIS AP
