SUMMARY:Allozyme variation of diploid loach Misgurnus anguillicaudatus was examined in samples collected from 44 localities in Japan. Genetic differentiation was estimated based on allele frequencies of 12 enzyme loci. Nine loci (36.9%) were polymorphic «0.95 in major allele frequency) and average heterozygosities were unusually high (Ho=0 .110±0.051, He=0.131 ±0.052). The coefficient of gene differentiation (Gst=0.774) suggested high genetic differentiation among populations. Based on the unweighted pair-group method using arithmetic averages (UPGMA) dendrogram, loach populatiqns were grouped into six clusters. The population of Memanbetsu, Hokkaido (group 1) was remarkably different from others (0=0.286). Populations distributed in Niigata, Nagano, Tochigi, Saitama, Chiba and Shizuoka Prefectures (group 6) were also genetically distinct from other loaches (0=0.192). These results suggest genetic differentiation among groups 1,6, and other loaches may be inter-subspecies level. Other loaches could be separated to four clusters (groups 2-5) at 0= 0.100-0.065. Genetic differentiation among them seems to be at local race level.

Genetic variation is a key component for improving a stock through selective breeding programs. Randomly amplified polymorphic DNA (RAPD) markers were used to assess genetic variation in three wild population of the catla carp (Catla catla Hamilton 1822) in the Halda, Jamuna and Padma rivers and one hatchery population in Bangladesh. Five decamer random primers were used to amplify RAPD markers from 30 fish from each population. Thirty of the 55 scorable bands were polymorphic, indicating some degree of genetic variation in all the populations. The proportion of polymorphic loci and gene diversity values reflected a relatively higher level of genetic variation in the Halda population. Sixteen of the 30 polymorphic loci showed a significant (p < 0.05, p < 0.01, p < 0.001) departure from homogeneity and the FST values in the different populations indicated some degree of genetic differentiation in the population pairs. Estimated genetic distances between populations were directly correlated with geographical distances. The unweighted pair group method with averages (UPGMA) dendrogram showed two clusters, the Halda population forming one cluster and the other populations the second cluster. Genetic variation of C. catla is a useful trait for developing a good management strategy for maintaining genetic quality of the species.

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