Incidence of ulcer type of disease in wild fishes of Bangladesh

Disease occurred in wild fish species investigated in different water bodies like canals, ditches, beel, haor, flood plain in 17 districts of Dhaka division. Haemorrhagic lesions were observed on the body surface of affected fishes. Incidence of the disease in the investigated water bodies ranged from 0 to 100%. In total 19 fish species were found to be affected and prevalence of infection ranged from 0.0 to 100.0%. Channa punctatus and Puntius ticto were severely affected in all locations. Percentage of infection in these fishes ranged from 0.0 to 100.0. The highest infection was observed in Netrokona, Kishoreganj, and Mymensingh districts. Bacterial genera isolated from the lesions of these affected fishes were Aeromonas, Pseudomonas, Flavobacterium, Micrococcus, and Staphylococcus. Among these isolates Aeromonas was the dominant. Abundance of Aeromonas in the lesions among the investigated bacteria ranged from 75 to 90%. Five identified Aero monas lrydrophila were examined for their pathogenicity and were able to infect the experimental fish, silver barb (Puntius gonionotus). The pathogen Aeromonas hydrophila was thus considered to have an association with the outbreak of ulcer type of disease in the investigated fish species.

Growth and survival rates of hatchery-produced and wild milkfish fry grown to fingerling size in earthen nursery ponds

Growth and survival rates of hatchery-produced and wild milkfish (Chanos chanos ) fry grown to fingerling size were compared. Data show no significant difference between the 2 fry. At a recommended stocking density of 30 fry/m super(2), hatchery-produced milkfish fry could attain fingerling size of almost 2g with a survival of 68%. The study indicates that hatchery-produced fry/fingerlings can equal the culture performance of the wild fry. Comparative performance of hatchery-bred and wild fry should encourage intensified research on milkfish broodstock development and refinement of induced spawning methods.

Effects of exogenous hormone injections on milt consistency in newly caught, wild milkfish

A study was conducted to determine the effects of single injections of human chorionic gonadotropin (HCG) and Durandron Forte 250 on sperm motility, vitality and density and also on the consistency of milt in newly caught, wild, mature milkfish (Chanos chanos). In contrast to HCG, single injections of Durandron Forte 250 were effective not only in inducing spermiation but also in maintaining newly caught mature males in good running condition for a maximum of 7 days, despite daily handling and collection of approximately 3ml milt.

Effect of different sex ratios of ablated wild-stock Penaeus monodon Fabricius on maturation, fecundity and hatching rates

The study was conducted to determine other sex ratios of ablated wild-stock Penaeus monodon other than the most commonly practiced 1 male: 1 female. Four different sex ratios, 0:1, 1:1, 1:2, and 1:4 male: female were tested in four 4m diameter circular tanks for a period of 55 days. During the first run the 1 male: 2 females ratio gave: (a) the highest percentage of first (42.20%), second (30.00%) and third (33.33%) spawning; and (b) the highest total and average fecundity (3.9 million eggs and 300,692 eggs, respectively). The 1 male: 2 females ratio is recommended on the basis of highest percentage for the first, second and third spawners, total and average fecundity.

Environmental impact of wild shrimp seed collection with non-selective gears on coastal aquatic biodiversity

Collection of wild tiger shrimp (Penaeus monodon) seed with non-selective gears and its impact upon the coastal aquatic biodiversity has been investigated. Loss of undesired species as by-catch was estimated to be 1,075 individuals for collection of every desired shrimp seed which amounted to be 132 billion in a study area stretching 3 km long coastline of the Sagar Island under the Sunderban Biosphere, West Bengal, India. Non-penaeid shrimp seed and crab larvae accounted to be maximally destroyed as their overall contribution towards the by-catch were 56.5% and 29.44%, respectively. Though, rate of bycatch loss was found to be inversely correlated with the rate of shrimp seed collected per gear (r=-0.82, p<0.05) during the peak season (May-September), the overall relationship between them exhibited a linear relationship (r=0.73, p<0.05). By-catch loss for every shrimp seed collection tended to increase up to a daily collection of 2,500 numbers of shrimp seeds per gear followed by a decline. Coastal aquatic community was maximally damaged when the heterogeneity and stability as reflected by different diversity indices were higher.

Comparison of physicochemical properties of muscle proteins in cultured and wild prawns (Penaeus (Fenneropenaeus) orientalis Kishinouye, 1918)

Protein physicochemical properties in cultured and wild prawns (Penaeus (F.) orientalis Kishinouye, 1918) were studied and compared. Protein fractions were separated into water-soluble, salt-soluble, alkali-soluble, and stroma. The results showed that salt- and alkali-soluble proteins were slightly higher in wild prawns and water-soluble proteins were higher in cultured prawns. There were only slight differences in Ca super(2+)-ATPase, MG super(2+)-ATPase, and ATP sensitivities. The textural values of wild prawns were significantly higher than the cultured ones.