An adequate supply of hatchery produced shrimp fry is the major constraint to the intensification and growth of shrimp culture practices. If even 20% of the more than 500,000 ha of the world's existing tropical and sub-tropical brackishwater ponds were to stock at the relatively low density of 50,000 fry/ha/year, it would take thousands of new hatcheries to produce the 25 billion fry required. The availability of artificially produced diets to replace cultured live food organisms would alleviate many of the problems currently limiting shrimp hatchery production by: (i) reducing the level of technical skill required to operate a hatchery; (ii) assuring a reliable supply of a nutritionally balanced larval feed; (iii) reducing sources of contamination and larval disease; and (iv) simplifying hatchery design and capital cost requirements, thereby facilitating small scale hatchery development. Aquatic farms has been working with the Mars Microencapsulation Research Group (MMRG) to develop techniques for adapting current shrimp hatchery technology and design so that MMRG feeds can be used in existing hatcheries as a live feed replacement. Feeding trials have been conducted in commercial hatcheries in Hawaii, Malaysia and Thailand. The results of these trials and the techniques employed are discussed. Growth and survival of larvae fed microencapsulated diets as total or partial replacement of live foods was comparable to larvae cultured in control tanks using the standard operating procedures of the hatchery in which the trials were conducted. In trials to date, larval survival from nauplii to postlarvae has been as high as 70%.

There are very few reports on the diseases, parasites, commensals and fouling in penaeid prawns. During the regular collection of marine and estuarine prawns in the east coast of India, a number were found to be infested with various organisms. The prawn Penaeus (Fenneropenaeus) indicus, was infested with a microsporidian which causes a condition known as milk or cotton prawn. The infestation was spread throughout the abdominal musculature of the prawn. The marine prawn Parapenaeopsis stylifera had epibiotic growth of athecate hydrozoans, probably of the genus Tubularia, on the dorsal side of the carapace and abdominal segments. This is the first report of athecate hydrozoans infesting the prawn. The prawn Metapenaeopsis stridulans was observed to be parasitized by a bopyrid isopod, Orbione thielemanni and the prawn Sicyonia lancifera, parasitized by another bopyrid isopod, O. kemi. The bopyrid isopod O. kemi infesting the prawn S. lancifera is also recorded for the first time. Both bopyrid isopods were found in the branchial cavity of the prawns. The Pontoniinid prawn Chernocaris placunae is a commensal living in the mantle cavity of the bivalve, Placenta placenta. Barnacles were found attached to the carapace and first abdominal segment of the prawn, Parapenaeopsis uncta, whereas they were found in the telson region also in the prawn P. stylifera. Most of the barnacles were very small with a basal diameter of less than 1.5 mm.

The tiger prawn of India, Penaeus monodon Fabricius has a differential distribution in the two coasts of India. Density is high in the northeastern part of the Bay of Bengal gradually declining towards the mid-east and becoming quite scarce towards the south. On the west coast, the distribution is more sparse and limited to a few months, off Bombay. The only known inshore areas of capture fisheries are the Godavari estuarine system, and the lagoons off Orissa at Chilka and Madras at Pulicat. The only known offshore capture exists off the Orissa coast at Paradip and Puri extending south to Visakhapatnam and Kakinada Bay. The greatest production comes off the brackishwater "bheri" (wild culture) system in the extensive "sunderbans" of West Bengal on the northeast where millions of seed recruited to the Hooghly estuarine complex are drawn in along with tidal waters and "cultured." The distribution profoundly affects the maturity, breeding and recruitment of this highly euryhaline species. The distribution can be related to the cyclic currents in the Bay of Bengal which have a profound effect on the salinity and temperature profile. It can also be related to the immense quantity of freshwater inflow from the mighty Hooghly-Matlah-Roopnarayan Padma estuarine complex at the head of the Bay and the other major riverine estuaries on the mid-east coast viz., the Mahanadi, Godavari and Krishna. The pattern of circulation and estuarine flows is such that it might also positively influence the food distribution, both live and detrital, in this region. Ripe (gravid) and ripening females and males of P. monodon in the size range of 100-250 g are captured off Paradip coast in the not very deep (30-40 m) waters where coastal trawlers operate, from October through April corresponding to the post-monsoon stability in the water movement and the increasing salinity. This offers a good augury for setting up hatcheries in adjacent zones using naturally mature forms. Catch records from one major freezing plant are presented to indicate the density and distribution of the species at the Paradip-Puri coast.

There are a number of intrinsic and extrinsic factors which affect the normal routine activity of the prawn. The present study attempts to elucidate the optimum levels of various environmental factors for the culture of prawns. The salinity tolerance capacity of Penaeus (Melicertus) latisulcatus was estimated in 13 different test salinities from 0 to 60 ppt (at 5 ppt increments). The prawns can tolerate a wide salinity range of 20-50 ppt. Maximum survival, however, was between 25 to 45 ppt. The extreme low (0-10 ppt) and high (60 ppt) salinities were highly lethal to the prawns. The change in acclimation temperature from 30 to 35°C increased the upper incipient lethal level from 38.5 to 39.5°C. The prawns acclimated to 30°C tolerated 42°C for 275 sec and 45.5°C for 13 sec, while prawns acclimated to 35°C tolerated 42°C for 505 sec and 46.5°C for 11 sec. Prawns were acclimated to a salinity of 26 ppt and oxygen consumption was measured at 5, 15, 26, and 38 ppt in a continuous water-flow method. The total oxygen consumption showed an inverse relationship with weight. Oxygen consumption declined with increase in salinity. The resistance of prawns to hydrogen sulphide was tested in 18 different concentrations of sodium sulphide mixed with seawater. The prawns tolerated sodium sulphide concentrations up to 20 mg/ℓ. The dissolved oxygen in the water was found to be reduced to very low levels with the increase in the concentration of sodium sulphide (from 5.9 ml O2/ℓ to 0.54 ml O2/ℓ). This may cause heavy mortality of the prawns.

The tissue lipid content and fatty acid composition in the hepatopancreas, tail muscle and gonad of unablated and ablated Penaeus monodon were determined. Females at various stages of maturity were collected from offshore spawning grounds in Tigbauan and Guimbal, Iloilo, Philippines. Ablated females were reared in captivity. The hepatopancreas showed the highest lipid content at 15.72 to 25.20% in unablated females and 22.47 to 34.90% in ablated females. Fresh lipid levels averaged 2.60% with no marked variation throughout the maturation period. Ovarian lipid increased from 5.80% (unablated) and 7.50% (ablated) in Immature Ovaries to more than two-fold in Early Maturing Ovaries coupled with a drop in hepatopancreatic lipid suggesting lipid mobilization to the ovaries. In ablated females, ovarian lipid progressively increased to a maximum of 21.90% in Fully Mature Ovaries with a corresponding rise in hepatopancreatic lipid. Both the ovarian and hepatopancreatic lipids declined in spent females. Fatty acid profiles of the tissues consistently showed the presence of polyunsaturated fatty acids (PUFA) 20:4ω6, 20:5ω3 and 22:6ω3. These fatty acids were reflected in the spawned egg. The lipid level in the hepatopancreas appeared to be inversely related to the total PUFA concentration in the ovaries. Lipid accumulation in ablated females was significantly higher than in unablated females. The findings suggest storage and subsequent utilization of lipids for maturation and spawning processes. The type of polyunsaturates present in the maturing ovaries is indicative of their metabolic and physiological importance in the reproductive process.

The thermal tolerance of four larval stages of Metapenaeus bennettae was studied in the laboratory. Critical Thermal Maximum (CTM), One hour Median Lethal Temperature (lhLT50), and Median Resistance Time (MRT) were measured. Moulting rate of larvae and hatching rate of embryos were also monitored to study the delayed effect of thermal stress. Thermal tolerance was shown to be strongly dependent on acclimation temperature (TA) at all larval stages,which showed ontogenetic development of thermal resistance. Moulting of larvae was hindered at temperatures (37.2°C for nauplius when TA=25°C) well below lhLT50 (38.1°C for nauplius when TA=25°C). The embryonic stages were more susceptible to thermal stress than the larval stages. The salinity effects were also significant. Nauplius and protozoea stages showed their highest CTM values at the salinity in which they were spawned.When compared with another penaeid M. macleayi (offshore breeder), M. bennettae (estuarine breeder) was found to have higher thermal resistance, but was less adaptive to changes in acclimation temperature.

Detrital food chains, based on the use of manures and compost have been used in aquaculture for centuries. Heterotrophic bacteria convert organic detritus into protein and thus constitute an important food source in ponds. Bacterial growth rates, and thus productivity, in natural environments can be calculated from the rate of tritiated thymidine incorporation into DNA. Rates of oxygen consumption by bacteria can be estimated from values for production. The tritiated thymidine method has been used to measure bacterial production in aquaculture ponds where a pelleted food was fed to penaeid prawns. It was found that most of the pelleted food was supporting bacterial growth, with bacterial production ranging from 0.43 to 2.1 mgCℓ–1d–1 in the water and 150 to 500 mgC m–2d–1 in the sediment. Bacterial biomass and growth rates were shown to be regulated by meiofauna, which in turn were eaten by the prawns. Primary production was not significant in the ponds. More oxygen was consumed by bacteria in the water column than was produced by photosynthesis of phytoplankton. Average shrimp yields at harvest were: chicken manure, 262 kg/ha; cow manure, 218 kg/ha; feed, 387 kg/ha; and control, 160 kg/ha. Average survival for each treatment was 50, 76, 58 and 79%, respectively. The percent yield of P. vannamei: P. stylirostris: P. occidentalis by weight for the four treatments was 85:15:0, 87:13:0, 78:22:0, and 92:9:0, respectively. P. occidentalis suffered 100% mortality during the production period. Average weights of shrimp at harvest were 8.72, 7.32, 12.07, and 5.98 g for the respective treatments. Ratios of average individual weights for P. vannamei: P. stylirostris for the treatments were 2.00:1, 1.99:1 and 2.22:1, respectively. Manures and feed significantly increased yield over the control (P< .0002). Feed significantly increased yield over that of the manures (P < .0001); while yields for manures did not differ (P > .05). Survival was not significantly different among treatments (P > .05).

Due to low nauplii production from cultivated broodstock and to minimize dependence on wild stock, an experiment was run in which four treatments, consisting of combinations of 400 adult blue shrimp (Penaeus stylirostris) from wild and cultivated (F6) populations, were applied (wild females and males, wild females and cultivated males, cultivated females and wild males, and cultivated females and males). Females were inspected every third day. Those observed with spermatophores were captured and transferred to individual 100-ℓ spawning tanks. Water was treated with EDTA and erythromycin phosphate. More than 300 individual spawns were evaluated within a 180-day period. To evaluate the nauplii production per female, an analysis of variance for a factorial arrangement (43 × 2) was conducted. The factors considered were: the abovementioned treatments, different ovarian maturation stages, adhesion of the spermatophore, and kind of spawning (complete or partial). The mixed populations had higher nauplii production than the cultivated broodstock. All the females were tagged around an eyestalk and examined for rematuration. Up to six rematurations per female were registered as well as a minimum of four days between successive spawnings for the same female. The effect of rematuration on the quantity of nauplii is discussed. Gonadosomatic index for wild and cultivated females is compared. Selective criteria for spawners are given.

The food value of five clones of Haptophyceae, Coccolithus pelagicus, Dicrateria zhanjiangensis, Isochrysis galbana, Tahitian Isochrysis aff. galbana, and Pseudoisochrysis paradoxa were tested for larval Penaeus orientalis. The algae were semi-continuously cultured in 5,000 ml carboys with 4,000 ml of Guillard f/2 medium, under 2,000 lux continuous light and under aeration. The algal density was up to 1 × 107 cell/ml. Rearing experiments were conducted in round tanks with diameter of 45 cm. Algal density was controlled at 1 × 105 cell/ml in the course of the experiments. The larval density was 18 individual/100 ml; water temperature, 21-24°C; pH, 7.5-7.7; and sea water specific gravity, 1.019. The results showed that of five clones used, Tahitian I. aff. galbana and D. zhangjiangensis proved to be the best. It took 9-11 days for nauplius I to develop into mysis I with survival rate of 73.5% and 73.4%, respectively.

Penaeus japonicus, P. vannamei and P. marginatus cultured at the Oceanic Institute in Hawaii, were sampled and measured. The shrimps sampled ranged from 1 to 15 g in body weight. The measurements included carapace length (CL), body length (BL), total length (TL) and body weight (BW). The results showed significant linear relationships between TL and CL, BL and CL. The relationships between CL and BW, BL and BW, TL and BW are well expressed by exponential curve. These relationships were found for all three species. However, P. japonicus has more similar morphometric characteristics to P. marginatus than P. vannamei. The carapace portion in P. vannamei is smaller than either P. japonicus or P. marginatus. In other words, P. vannamei has a greater edible portion than P. japonicus and P. marginatus. Equations for length-weight relationships can provide means of converting one characteristic into another.