Yngelproduksjon av gadoider: utvikling av
intensiv oppdrettsmetode for torsk og hyse.
(Juvenile production of gadoids: development of intensive rearing methods
for cod and HADDOCK, in
Norwegian)
Project report by T. van der Meeren and V. Ivannikov
Institute of Marine Research, Nordnesparken 2, Postboks 1870, 5817
Bergen, Norway
Rapport Fisken og Havet, Nr. 2 – 2001
Abstract:
Rearing of cod juveniles has been based on production in extensive lagoon
systems with use of ambient zooplankton as food. However, such systems are
limited by low production densities, only one yearly production cycle, and
little control over vital production parameters (e.g. prey availability).
Development of intensive rearing methods with algae, rotifers, and Artemia
is therefore needed, because this may give season-independent and
predictable production under controlled conditions. The objectives of the
project was therefore to provide the base for season-independent juvenile
production of cod through shift in broodstock spawning season and test of
larval viability originating from such broodstocks.
Broodstock fish from two year classes produced in the lagoon
“Parisvannet” (Institute of Marine Research, Bergen) were moved indoor
in February to a shift of 6 months in photoperiod. To postpone gonad
maturation, one of the year classes got additional 24 hours light in the net
pen from September. Ultra sound was used to check maturation of the gonads.
Control of spawning time was simple in cod. The broodstock without
additional light in the net pen spawned both spring and autumn, while the
fish with additional light in the net pen spawned only during autumn. All
spawned eggs were collected, and quality evaluated from visual inspection.
Broodstock temperatures above 10° resulted in reduced fertilisation,
increased rate of abnormal egg development, and increased egg mortality of
fertilised eggs. To test viability, egg groups were incubated, hatched and
transferred to startfeeding. The startfeeding results during the autumn were
promising, with survival between 30 and 50% from 44 to 46 days after
hatching (fish size of 12-15mm standard length). However, growth rates were
low, indicating a potential for considerable improvements in feeding
procedures and tank dynamics trough the larval stages.