Predation on herring (Clupea harengus) eggs and young larvae.
Working paper
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http://hdl.handle.net/11250/103597Utgivelsesdato
1980Metadata
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This report is not to be quoted without prior consultation with the General Secretary.Sammendrag
The study presented here is part of a greater project dealing
with recruitment studies of a local herring stock in Lindåspollene
north of Bergen.
Fish predators on herring spawn, mainly cod and haddock, were
trapped in entangling nets near the spawning ground during 1978,
1979 and 1980. On the basis of stomach contents of these fish
species, one has tried to estimate to which degree fish predation
on herring spawn influences total egg mortality. During years
with moderate and heavy spawning, fish feeding on herring eggs
seems to play a minor role in Lindåspollene, but during years
with ligh spawn (1978), fish predation was estimated to make up
maximum 40-60% of total egg number. These estimates depend
closely on fish abundance which is insufficiently known. On the
basis of mean stomach contents and values obtained from the
literature on food consumption and daily energy requirements,
a cod specimen has been calculated to ingest about 15-20 000 eggs
daily.
Staging of herring eggs in fish stomachs indicates that the
natural mortality of herring eggs is variable, and increases
towards the time of hatching.
In situ observations of planktonic invertebrates preying
on newly hatched herring larvae, confirm the presumably high
predator potential of planktonic invertebrates previously
reported (FOSSUM and JOHANNESSEN 1979). Bolinopsis sp. and
Sarsia sp. especially, but also Pleurobrachia sp. and other medusae-species were recorded in situ preying on herring larvae.