Preliminary report on the effects of temperature on the development of eggs and larvae of halibut (Hippoglossus hippoglossus) and on the bacterial population in the incubators
Bergh, Øivind; Opstad, Ingegjerd; Pittman, Karin; Skiftesvik, Anne Berit; Skjolddal, Lillian; Strand, Hans Kristian; Vanthuyne, Virginie
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http://hdl.handle.net/11250/104607Utgivelsesdato
1989Metadata
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This report is not to be cited without prior reference to the authorsSammendrag
Eggs were stripped from one female of the halibut broodstock at Austevoll Aquaculture
Station, and fertilised with sperm from two males immediately before incubation. Eggs
were held in nine open-circulation 250 l incubators at either 3°, 6° or 9°C with three
incubators at each temperature. When hatched, the larvae were transferred to fifteen
similar incubators, with five incubators at each temperature. The timing of
developmental events in the eggs and larvae was monitored, mortality in the egg and
larval stages recorded, growth and yolk absorbtion measured in the larvae, RNA and
DNA content and RNA/DNA ratios determined for each temperature group and samples
taken for embryonal and larval histology. Total and viable count of free-living
bacteria in the incubators was monitored from hatching until termination of the
experiment. Flow rate, temperature, oxygen and ammonia were recorded.
Differences in development rates were apparent from the first cell divisions. The mean
number of Kuppfer's vesicles was most in the 9°C groups and least in the 6°C groups.
At hatching, relative protein synthesis and yolk sac size was best at 3°C but there was
no difference in standard length between the groups. At 9°C, larvae grew faster, but
developed abnormalities associated with sublethal stressors. A rise in mortalities
occurred at the same stage of development at 6° and 9°C. An increase in larval
mortalities lead to an increase in bacteria which preceded an increase in ammonia
levels. There was no significant difference in bacterial numbers between groups. The
experiment was terminated due to uncontrolled temperature fluctuations.