| dc.description.abstract | Detailed genetic analysis have provided valuable information about
the population structure of several commercially important fish
species. The investigations have mainly concentrated on the problem
on stock identification, and recently to the concervation of genetic
resources.
The method of enzyme electrophoresis utilize small pieces of fish
tissue which can easily be obtained during the biological sampling
of fish populations. In tagging experiments, however, it has been
impossible to get tissue samples for genetic analysis. For this
reason, a biopsi apparatus was constructed which permit one to take
small pieces of white muscle from alive fish. The apparatus is
described below.
The biopsi apparatus was tested on a tagging cruise in the Møre
area during the spawning season of cod. Sampling of white muscle of
cod was easily to perform, and the fish were tagged in the conventional
manner afterwards. The samples taken by biopsi were frozen
and later analysed in the laboratory for the polymorphic enzymes
phosphoglucose isomerase (PGI), phosphoglucomutase (PGM), lactate
dehydrogenase (LDH), isocitrate dehydrogenase (IDH) and a-glycerophosphate
dehydrogenase (GPD) .
The enzyme activities in the samples were high, and thus permitting
classification of each individual fish to enzyme phenotype. About
600 fish were both tagged and classified to phenotype for most of
the enzymes in question. Comparisons of phenotypes and allel frequencies
indicated heterogenity between different catches during
the cruise. Some catches, mainly consisting of immature cod individuals,
differ significantly from the others. Preliminary data on
recapture of tagged fish, suggest that this fish belong to cod
occurring in coastal sea water. The material, however, was limited
and more data are needed to get a better knowledge of the population
structure of cod in the Møre area. | en |
