A northern Indian Ocean record of a bopyrid, Parapenaeon japonica (Thielemann, 1910) parasitic on species of penaeid prawns (Penaeus)

A female of Penaeus merguiensis de Man collected from Karachi fish harbour (8 May, 1993) was with a large specimen of bopyrid in its right gill chamber. Since this was the second record (see Tirmizi and Bashir, 1973) of a bopyrid from a species other than Parapenauopsis stylifera H. Milne-Edwards the specimen was examined out of curiosity.

A study on damage caused to crustacean and finfish larvae during collection of Penaeus monodon (Fab.) postlarvae in the estuaries of Barguna, Bangladesh

A year round investigation in the estuaries of Barguna district revealed that for each Penaeus monodon postlarvae (PL), about 37 larvae of other shrimp species, 12 finfishes and 10 macrozooplankters are destroyed during the process of shrimp seed collection. Although abundance of P. monodon PL was not recorded throughout the year, a significant number of other shrimp spp., fin fishes including macrozooplankters are being damaged by the shrimp seed collectors. This indiscriminate destruction of aquatic organisms during P. monodon PL collection is serious threat to aquatic biodiversity.

Effect of stocking density on growth of tiger shrimp (Penaeus monodon Fab.) fed on commercial formulated diets

Three different stocking rates in a semi-intensive pilot shrimp project was adopted in duplicates of three treatments designated as T1, T2 and T3 having initial per meter square stocking density of shrimp of 40, 44 and 51 respectively of 0.025g size post larva. The study was conducted for 84 days. Commercial pelleted diets designated as starter - 1, 2, 3 and grower were fed at a satiation level during the study period with a feeding frequency of 4 to 5 times per day. Feed rationing was based on the survivability, body weight and tray checking. 5-25% of the pond water was exchanged daily. Sampling was done for growth after every 2nd week. Monthly sampling was done for mortality in the ponds. Mean weight gain of the shrimp in treatments T1, T2 and T3 were 16.96 ± 1.14, 16.04 ± 1.38 and 14.08 ± 1.17g respectively and T1 with a low stocking density showed a significantly best growth among the treatments. Total mortality in treatments T1, T2 and T3 were as 30.00, 39.77 and 31.37% respectively. Significantly higher feed conversion ratio (FCR) of 1.87 was obtained with shrimp in treatment T3 followed by shrimp in T1 and T2 with FCR values of 1.70 and 1.41 respectively. A positive correlation of growth and salinity was observed during the study. Total production per unit area was the highest in the treatment T3 (4928 kg/ha) and followed by T1 (4747 kg/ha) and T2 (4251 kg/ha). The result show significantly negative correlation between individual growth and density.

Environmental parameters and incidence of white spot disease in Penaeus monodon (Fab.) farming

An investigation was carried out to monitor management practices and to find out whether there is any relationship with occurrence of deadly white spot disease and environmental parameters. Three semi-intensive and a improved traditional shrimp farms were selected in which mass mortality of shrimp (Penaeus monodon) by white spot disease occurred previously. The farms were situated at two different geographical locations. Two ponds from each farm at random were selected for the study. Out of eight investigated ponds, 6 ponds in three farms were affected by the disease during investigation period. The non-affected ponds had relatively lower stocking density, lightly different management practice and were located at different geographical area. There was no significant variation in water quality parameters among the affected and non-affected ponds. No significant variations were recorded in pond preparation, source of Post Larvae (PL), water and feed management among the affected and non-affected ponds. The observation indicated that pond micro-organisms in a farm may not the only cause of the disease but some external factors also might be responsible for the outbreak of this disease.

Colossal loss of shell and fin-fish larvae during collection of Penaeus monodon (Fab.) fry in the rivers of Satkhira

This study was conducted in five river-estuaries of Satkhira from January to December '96. It was found that during the collection of each Peneaus monodon) post larva (PL), about 45 larvae of other shrimps, 12 individuals of fin-fishes and 530 macro-zooplankters were mercilessly destroyed. It was also recorded that about 11.6 million of P. monodon PLs were harvested annually from the study area. The sh1dy implies that colossal loss of shell and fin-fishes and other plankton resources is done by tiger shrimp fry collectors, and such massive destruction adversely affect the natural productivity and ecological balance of the coastal environment.

Food preference and intake pattern of Penaeus monodon (Fab.) in semi-intensive culture system

P. monodon juveniles prefer natural food than artificial feed in their initial stage of rearing. However, the percentage preference towards artificial feed increases as the days of culture/average body weight increases. Consumption of artificial feed was high during evening meal (1700h) and low during night meal (2200h). The index of intestine fullness was high (8.4±0.7) during initial stage of rearing, compared to that of final stage of rearing (4.9±0.4), probably due to low nutritional value of intake material and low water depth at initial stage. At all stage of rearing omnivorous feeding habit was established and no evidence of diet periodicity in feeding activity was observed.

Effect of submerged aquatic vegetation on growth and survival of Penaeus monodon (Fab.)

An experiment was conducted in brackish water ponds with transplanted aquatic weed (Najas sp.) to study the effect of submerged aquatic vegetation on culture of Penaeus monodon. Out of six ponds three were without any aquatic vegetation (T1) while in other three ponds weeds were planted covering 40% of the pond bottom (T2). Hatchery produced post larva of P. monodon (0.006 g) were stocked in all ponds at a density of 40,000/ha. Shrimps were fed twice daily with commercial and formulated feed prepared from locally available ingredients. After 105 days of rearing shrimp of highest average weight (63.18g) was obtained from T2 with a survival rate of 25.90% and the total production was obtained at 654.54 kg/ha. The average weight, survival and total production of shrimp in T1 were 35.0 g, 28.76% and 405.63 kg/ha, respectively.

Water quality management on the enhancement of shrimp (Penaeus monodon Fab.) production in the traditional and improved-traditional ghers of Bangladesh

On-farm research on enhancement of P. monodon production through water quality management was carried out in five ghers of Paikgacha, Khulna. Based on the prevailing condition of the ghers, lime in the form of CaCO(sub 3), urea and TSP were used as the major inputs to minimize the soil-water acidity and to ensure the availability of natural food particles in the water bodies. Exchange of water at required level also practiced for the qualitative improvement of culture water. Ghers of varying sizes showed that water quality management and fertilization have a positive impact on production performance of P. monodon (61.59% increment) that yielded an average production of 385.43 kg/ha/crop against the present traditional rate of 238.50 kg/ha/year.

Observation on the production performance of Penaeus monodon with Liza parsia under different cropping system

Study was conducted in six ponds each with an area of 0.1 ha in the pond complex of Brackishwater Station, Paikgacha, Khulna from February to October '96, to find out the variation of production rate in two culture system viz., single and double crop of P. monodon with L. parsia. In treatment T1 wild fry of P. monodon (0.006g) and L. parsia (0.20g) collected from nearby river were stocked at a rate of 40,000 and 10,000/ha, respectively, for a culture period of 120 days. In treatment T2, the rate was 20,000/ha for bagda fry in 1st and 2nd crop each and 10,000 for parsia fry/ha for an extended period of 225 days. The highest survivability and growth of P. monodon and L. parsia were 57.08% (1st crop of T2) and 75.26% (T2), and 27.08g (1st crop of T2) and 47.78g (T2), respectively with a significant variations (P>0.05) with other treatment. The net profit (Tk. 93,134) and cost benefit ratio of 1:1.76 were also found higher in T2.

A study on food and feeding habits of Nemipterus japonicus (Bloch) off Bombay coast

The gut content of Nemipterus japonicus revealed that this fish is a carnivorous bottom feeder, feeding mainly on crustaceans, fishes, salps and polychaetes, with marginal variations in females. The intensity of feeding increased with the advancement of maturity till stage 5 except in stage 3 where the intensity of feeding indicated a decrease.

Studies on the effect of compounded feeds on the growth of juvenile Banana prawn Penaeus merguiensis

Laboratory experiments were conducted to determine the effect of compounded feeds on growth of juveniles (3 to 4 cm) of the Banana prawn Penaeus merguiensis. In all, seven diets were prepared with different combinations of locally available ingredients. Diascure, a local tuber was used as source of carbohydrate and vitamin mineral mixture (1%) was used in all the diets. The results indicated that diets with groundnut cake (diet 2, 3, 5 and 7) produced better survival and growth. In diets 4 and 6 growth was good but survival was very poor. Amongst all the diets, diet 7 produced significantly better growth, survival and food conversion ratio.

Dietary cholesterol requirement of larvae and postlarvae of the prawn Penaeus indicus (H. Milne Edwards)

Two sets of experiments were conducted to determine the dietary cholesterol requirement of larvae and postlarvae 1-10 of Penaeus indicus. Seven approximately isocaloric and isonitrogenous purified experimental diets were tried with graded levels of cholesterol ranging from 0 to 4%. The control feed for larvae and postlarvae 1-10 were phytoplankton and compounded feed NPCL-17, developed by CMFRI, Cochin respectively. Result of these experiments indicates that cholesterol is an essential nutrient in the diet of larvae and postlarvae 1-10. Survival and growth of larvae and postlarvae 1-10 were greatly affected by cholesterol deficiency in the diet. The optimal cholesterol requirement for larvae appeared to be 0.5% of the diet, while it was higher for postlarvae where inclusion of cholesterol at a level of 2% in the diet gave higher growth.

Population dynamics of penaeid prawn Penaeus merguiensis off Mumbai coast

Stock dynamics of Penaeus merguiensis was studied using length composition data collected separately for males and females during the period 1995-1998, at New Ferry Warf landing, centre in Greater Mumbai. Food and feeding, sex ratio, fecundity and length-weight relationships were worked out on a representative sub-sample. Asymptotic length (Loo) and growth coefficient (K) were estimated to be 220 mm and 1.80 per annum respectively for males. These parameters were respectively 281 mm and 1. 72 per annum in the case of females. The instantaneous rate of total mortality coefficient (Z) was found to be 9.79 and 7.44 per annum for males and females respectively. The annual natural mortality coefficient (M) was estimated to be 2.80 for males and 2.60 for females. As the exploitation ratio exceeded 0.5 in the case of both the males and females, the study suggests the necessity for reduction in fishing pressure in order to achieve Maximum Sustainable Yield (MSY).

Penaeus indicus H. Milne Edwards, 1837: a summary of the conclusions from the fishing exploratory surveys between 1979 and 1837 at Sofala Bank, Mozambique

From 1979 to 1983, several surveys were carried out with research and fishing vessels at Sofala Bank in Mozambique. Their main objective was the assessment of shallow water prawn stocks, as this resource is of great economic importance for the country. A summary of the conclusions of these surveys regarding the species Penaeus indicus is presented. During the rainy season the species occurs closer to the shore than during the dry season. Estimates of biomass are very variable. The spawning peak seems to occur at the beginning of the rainy season (September-October). The spawning areas are located very close to the shore in the northern part of Sofala Bank and South of 17 degree 10'S in the 15-25 m depth interval.