Genetic diversity in the Indian population of the tiger shrimp Penaeus monodon was determined by using partial sequence data of the mitochondrial DNA (mtDNA) control region (D‐loop) and the 16S rRNA gene. Eight populations from different geographical locations (Mumbai, Kochi, Mangalore, Kakinada, Gopalpur, Chilika, Paradeep and Andaman) were collected and analysed. The amplified polymerase chain reaction products of size 577 bp for the control region and 472 bp for 16S rRNA were sequenced in both directions and data were analysed through clustal, arlequin, mega and phylip. A significant genetic structure was found among the Indian populations. The mtDNA control region proved to be a powerful marker in comparison with 16S rRNA for population studies of this species. The east coast population was more genetically diverse than the west coast. The Andaman population was found to be the most diverse among all the populations. The populations on the west coast were found to be genetically more structured and differentiated than the populations on the east coast. The results revealed a high level of genetic diversity and also distinct population structuring of P. monodon, suggesting great possibilities of genetic improvement for growth and other economic traits.

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A computer-aided semen analysis system was used to assess the % motile cells following storage of carp semen in 11 different buffers at 2, 5 or 22 C. BWW and TLP were the most suitable storage buffers because carp semen stored at 5 C in these buffers following activation showed no significant decrease in % motile spermatozoa up to 24 h. But, in most of the other buffers (Fish Ringer, Cytomix, Cortland, FRT, Mannitol, FPS, NAS and TSM) the motility potential was lost by 2 h. Storage was best at pH 6-9 and at 5 C. Carp spermatozoa exhibit three distinct motility patterns, namely 'linear', 'circular' and 'haphazard', the proportion of spermatozoa with a particular motility pattern depending on storage buffer and time. All spermatozoa with a linear trajectory had high VSL, STR and LIN; those moving in circles had low VSL, STR, LIN and BCF and those with a haphazard trajectory were distinct in that they had the highest ALH and their VSL, STR, LIN and BCF were higher than the circular moving spermatozoa and lower than the spermatozoa exhibiting linear trajectory. The study also demonstrates a pronounced time-dependent decrease in VCL, VAP, VSL and ALH of carp spermatozoa following activation with water or low osmolality solutions. This study provides for the first time data related to seven motility parameters of carp spermatozoa and demonstrates how these parameter values could be used to evaluate quality of carp milt following storage in different buffers. It confirms that carp spermatozoa exhibit linear or circular trajectories and provides evidence for a third type of trajectory described as haphazard. All three motility patterns could be discriminated objectively on the seven motility parameters. 1997 The Fisheries Society of the British Isles

Mitochondrial DNA, cytochrome oxidase-1 gene sequences were analyzed for species identification and phylogenetic relationship among the very high food value and commercially important Indian carangid fish species. Sequence analysis of COI gene very clearly indicated that all the 28 fish species fell into five distinct groups, which are genetically distant from each other and exhibited identical phylogenetic reservation. All the COI gene sequences from 28 fishes provide sufficient phylogenetic information and evolutionary relationship to distinguish the carangid species unambiguously. This study proves the utility of mtDNA COI gene sequence based approach in identifying fish species at a faster pace.

Genetic similarity and diversity of catfish Clarias batrachus (Linn.1758) populations collected from three regions of Indian riverine system were examined using randomly amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR). Out of 22 random primers tested, six primers produced 462 RAPD bands ranging from 105 to 128 polymorphic bands per primer in size between 100 and 1,200 bp. The polymorphic bands in these populations ranged from 26.5 to 30.5. Polymorphic bands within populations ranged from 25 to 35.7%. The degree of similarity within Hussainabad population varied from 0.125 to 0.842 based on average level of band sharing (BS) values. The level of band sharing values within the catfish populations were 0.26 +/- 0.021 for Banaras, 0.60 +/- 0.033 for Bhubaneshwar and 0.377 +/- 0.058 for Hussainabad respectively. The results from the present study indicate that there is great degree of genetic similarity between Bhubaneshwar and Hussainabad populations where as Banaras catfish population is distinct. It may appear that Bhubaneshwar and Hussainabad are geographically connected by rivers and most of the major catfish hatcheries are located in this region, therefore the individuals from these populations are get reared in the same environmental conditions, migration or by inbreeding during several generations may be possible. This may be the reason that catfish population is lacking genetic diversity in major riverine system of India. In nearer future, the lack in genetic diversity can lead to inbreeding which can be resulted in poor growth and disease susceptibility, Bhubaneshwar and Hussainabad catfish population may have this problem.