Genetic tsting of common carp in cages: 1. Communal versus separate testing

Abstract Relative growth rates of different genetic groups of common carp were tested simultaneously in cages stocked with a given genetic group (separate cages), and in cages stocked communally with samples of different genetic groups. The results of three tests are described. A clear association between relative growth of different progenies, in communal and separate testing, was found in one of these tests. The other two tests did not generate significant associations between relative growth in communal and separate cages, presumably as a result of an insufficient number of tested groups or of replications of separate cages. We suggest that, in cages, results from the convenient method of communal testing may serve as reliable predictors for relative growth of different genetic groups in separate testing. This should be confirmed in further, similar investigations. Previous tests in communally and separately stocked ponds generated a similar conclusion. On the other hand, genotype-environment interactions have been demonstrated when the same genetic groups were tested simultaneously in communal ponds and cages. This means that relative pond performance is not a reliable predictor for performance in cages, or vice versa. Cage culture is presently under consideration as a commercial production method for common carp. The investigations described here indicate that performance testing for choice of genetic stock for cage operations needs to be carried out in cages and not in ponds. Large scale production in cages is carried out, or planned, with several fish species. Genetic testing for these operations is carried out largely in communal cages. The methodology of this testing method been investigated only in common carp, by simultaneous testing of the same genetic groups in communal and separate cages.