A study was undertaken to evaluate the effect of stocking density on brood stock development of mud crab (Scylla serrate) in brackishwater earthen ponds. Four stocking densities such as 6000/ha (T 1); 8000/ha (T 2); 10000/ha (T 3) and 12000/ha (T 4) were tested and the crabs were allowed to fed with 50% slaughterhouse+25 percent tilapia (Oriochromis niloticus)+25% soft shrimp head. In terms of survival rate (both male and female) the stocking density having 6000/ha showed the best performance. For female crab significant lower survival (p<0.05) was observed for T 3 and T 4 compare to T 1 and T 2. But for final growth and carapace width, an insignificant variation was noted among the treatments. However, in case of T 1 and T 2 , 2.5-3.0 percent of females were found to became berried showing significant variation with other two treatments proved that high stocking has inverse effect on brood development.

An experiment was carried out at Brackishwater Station, Bangladesh Fisheries Research Institute, Paikgacha, Khulna from July to August, 1999 to assess the effect of feed on larval survival of Macrobrachium rosenbergii. Three treatments viz. Artemia nauplii plus egg custard (T 1), Artemia nauplii only (T 2) and rotifer-000 only (T 3) were taken for the study each with three replicates. The experiment was conducted in celluloid tanks with M. rosenbergii larvae at a density of 50 nos./litre of water. Highest average survival rate (30.0%) was found in T 1 and the lowest (4.5%) obtained in T3. Analysis of variance showed that the difference in larval survival under different treatments were significantly different (p<0.01). The results obtained implied that there is a immense potentiality for increasing freshwater prawn seed production through closed water system by using Artemia nauplii plus egg custard as feed.

Shrimps is one of the main export commodities of the country and earns about more than 40 crores 47 lac US $in 2017. Black Tiger (BT) shrimp alone contributes about 67 % to the total shrimp export per year. Aquaculture shrimps are being processed in the land-based processing plant while wild catch is being processed onboard (fishing vessels) in the Bay of Bengal. A study was conducted to compare the yield and economic loss/gain of headless shell-on (HLSO) shrimp during processing by labor and crews at onboard (sea) and land based (land) factories. A total of twelve samples were examined; six for land and six for sea that was designated as “P” and “V”, respectively. After beheading to produce HLSO, individual shrimp weight was measured. The average weight of an individual BT was 50.25 ± 4.174 g for V and 51.13 ±3.66 g for P. Average yield from individual shrimp was 1.19 g higher in P compared to V. Found 23.10 g less production from 1 kg BT in V compare to P which is statistically significant (P=0.057). Our estimated results indicated that one vessel got 649.89 Kg less product valued BDT 1,381,016 compare to land based processing plants due to processing by crews on board. Whole scenario predicts that more economic loss if we consider for 37 shrimp trawlers in operation. Bangladesh J. Zool. 48(2): 393-398, 2020

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The study was carried out in the Meghna river-estuaries of Bhola district from January, 1996 to December, 1997 with a view of quantify the extent of damage of shell and fin-fish larvae during collection of P. monodon larvae as target species. Study revealed that during collection of each Penaeus monodon (Fab.) post larva (PL), about 26 and 17 larvae of other shrimp, 16 and 7 fin-fishes and 90 and 39 macrozooplankters respectively were ruthlessly destroyed during the consequent years. During the study period, about 1.10 and 0.89 million man days/years, respectively were found to involve in shrimp fry collection. It was also recorded that about 11.0 and 8.2 million of P. monodon PLs respectively were harvested in 1996 and 1997 from the study area. The study indicates that indiscriminate killing of shell and fin-fishes and other valuable aquatic organisms during collection of P. monodon PL by shrimp seed collectors is causing threat to aquatic biodiversity conservation and ecology of coastal waters.