Determination of population structure and stock composition of chum salmon (Oncorhynchus keta) in Russia determined with microsatellites

Variation at 14 microsatellite loci was examined in 34 chum salmon (Oncorhynchus keta) populations from Russia and evaluated for its use in the determination of population structure and stock composition in simulated mixed-stock fishery samples. The genetic differentiation index (Fst) over all populations and loci was 0.017, and individual locus values ranged from 0.003 to 0.054. Regional population structure was observed, and populations from Primorye, Sakhalin Island, and northeast Russia were the most distinct. Microsatellite variation provided evidence of a more fine-scale population structure than those that had previously been demonstrated with other genetic-based markers. Analysis of simulated mixed-stock samples indicated that accurate and precise regional estimates of stock composition were produced when the microsatellites were used to estimate stock compositions. Microsatellites can be used to determine stock composition in geographically separate Russian coastal chum salmon fisheries and provide a greater resolution of stock composition and population structure than that previously provided with other techniques.

Possíveis relações entre a área de pesca, profundidade e tempo de imersão nas actividades da pesca com covos

A cruise aboard the vessel Cassiopeia was held from 14 to 22 November 2000. The objective to map the fishing areas, to study the variation of the catch, income, specific composition and length on wishbone Polysteganus coeruleopunctatus (cachucho) in relation to fishing areas, depth and immersion time of the fish pots. The total capture registered was 4.350,00 Kg for 1600 fish pots and 32 effectuated throws. The highest capture per throw was registered in the interval of depth between the 140 to 180 meters. Regarding the time of immersion, the better captures were obtained in the interval between 25 and 30 hours. The profits during this cross were for fish-trap (2, 71 kg), per throw 135,00 Kg and for immersion hour 6,07 kg. P. coeruleopunctatus (cachucho) was more abundant in number in Quissico, while in Zavora it was abundant in number and also in weight. Likewise, the cachucho was more abundant in number and weight in the captures of the fish pots submerged less than 24 hours, 100-140 meters depth. Cachucho catch under 100 meters depth was quite reduced (less than 1 %). The middle length of the cachucho captured during the cross was 275,7 mm. There were significant differences in the lengths of the cachucho accordingly to depth or fishing area. The smallest individual (fish) was captured by fish pots that were submerged more than 24 hours. The principal recommendations of the study refer to maintenance of the current fishing effort with regard to the number of fish pots, and explore the fishing areas on a rotating basis, to avoid the local effort, currently high.

Effect of lykamin on growth and biochemical composition of long whiskered catfish, Mystus gulio (Hamilton) fingerlings under laboratory conditions

A growth trial was conducted to test the effect of Lykamin (dietary supplement) on growth, survival and feed conversion in Mystus gulio. Four isoproteic diets were formulated by incorporating the growth promoter, Lykamin at the levels of 0, 0.25, 0.50 and 0.75% diet. The crude protein content was 30% in each diet. The diets were fed to triplicate groups of catfish fingerlings twice daily at a level of 5% of the total body weight for 120 days. Regular fortnightly sampling was done to evaluate the growth performance of the experimental animals. Water quality parameters during the experimental period were maintained within the range suitable for catfish. The results showed better specific growth rate, weight gain, protein efficiency ratio and feed conversion ratio in the group which was given 0.75% Lykamin diet.

Effect of starvation on the biochemical composition of Clarias batrachus (Linn.)

Marked changes were observed in different chemical constituents of C. batrachus during starvation. The N and protein fractions showed a definite pattern of variations. The highest values of these were recorded on 10th day of starvation and thereafter values declined gradually. On the other hand, the acid soluble phosphorus exhibited a reverse trend, increasing gradually from the first to the 30th day of starvation. These changes have been attributed mainly to the energy and metabolic demands of the starving fish.