Utilization of potential area for shrimp culture in the traditional system was very meager — just 1.8% of total estimated available area of 1.45 million ha. The traditional paddy and fish culture and paddy cum fish culture systems and the return on investment (ROI) are explained. To adopt intensive culture, there is adequate scientific information based on many successful achievements throughexperimental trials indicating body weight of 16.7 g in 45 days for P. indicus with more than 80% survival rate proving economic viability. Basic studies were also made to find out the seasonal seed availability in different regions. Shrimp production to the extent of 500-700 kg/ha was achieved in many demonstration ponds organized by the Marine Products Export Development Authority indicating commercial reality of shrimp culture in India. As vast potential areas are available, shrimp culture will minimize the present 75% idle capacity of the Indian seafood processing industry which is over-dependent on shrimp as its major product for export. Furthermore, adding more areas to culture has direct impact on the socio-economic status of the rural population. Three thousand self-employed people are now known to be directly engaged in seed collection. In addition, the shrimp farmer realizes returns two to three times more than his counterpart in paddy cultivation, in the same field and for more or less the same period of time. In West Bengal, of total export value of 43 crores, up to 25 crores is realized by farmers for their production of shrimp through culture reflecting better unit return for their raw material than that realized byprocessor/exporter of the end-product. Therefore, bringing additional areas under shrimp culture will directly affect the socio-economic status of the rural people employing an average of 5 persons/ha, and indirectly affect no less than 15,000 casual workers in the seafood processing industry by additional utilization of manpower and working hours. As productivity from capture appears bleak, brackish-water shrimp culture has been accorded top priority in India's national developmental programmes for more harvest from aquatic sources otherwise termed the "Blue Revolution."

As penaeid shrimp grow from the earliest naupliar stages, through protozoeal and mysis stages, to postlarvae, they develop greater morphological and behavioral resemblance to the adults. Electrophoretic analysis of cytoplasmic enzymes from nauplii, protozoea, mysis, postlarvae, and adults show that each stage has a unique pattern of gene activity. Thirteen enzyme stains and a general protein stain have been used on larval samples from Penaeus stylirostris, P. vannamei and P. aztecus. Some enzymes, such as phospho-glucose isomerase, are produced in the same isozymic form during all of the stages. Other enzymes exhibit changes in the number and position of isozymic bands during development, e.g. glutamate dehydrogenase. Some of these differences among developmental stages can only be explained by changes in the number and/or identity of the genes that are active at each stage. This finding suggests larval and adult responses to selection may be relatively independent.

Ecuadorian Penaeus vannamei were stocked in eight dirt ponds (approximately 163 m2) at four different types of density, i.e., 5 shrimp/m2, 10 shrimp/m2, 15 shrimp/m2, and 20 shrimp/m2. The initial body weight ranged between 1.1 and 3.8 g. No commercial feed was given to the shrimp. The only input to the pond was 30 kg of cow manure/week. Shrimp were sampled either weekly or bi-weekly for body weight measurements. Water quality parameters, such as temperature, pH, DO and turbidity were recorded twice daily; nutrients (nitrite, nitrate, ammonium and phosphate) and BOD were measured twice weekly. The chemical composition of the cow manure was analyzed. After 14 weeks' experiment, the shrimp were harvested, weighed and counted. Survival and total yield were compared among treatments. The results showed negative correlation between stocking density and growth. The weekly growth of shrimp was between 0.7 and 1.0 g. There was no relationship between stocking density and survival. Survival averaged 68%. The most suitable stocking density should be judged by profit. However, the total yield of shrimp was higher in the higher stocking density.

The response of Penaeus monodon juveniles (ave. wt.= 0.076 g) in terms of survival and growth rates to vitamin test diets was observed in a 35-day feeding experiment. The prawns were reared in 60-ℓ oval tanks containing filtered seawater in a flowthrough system of ambient temperature and salinity. The treatments consisted of a control (complete vitamin mix), a vitamin-free diet and nine other diets, each lacking one of the vitamins in the mixture. At the end of the feeding trial, the survival rates in all treatments ranged from 80 to 100%, while weight gain ranged from 74 to 40%. Significantly lower weight gains were obtained from choline chloride-free diet (P<0.05) and vitamin-free and inositol-free diets (P<0.01) than from control.

The response of Penaeus monodon juveniles (0.71±0.11 g) to varying protein/energy ratios in test diets was determined. Purified diets consisting of different levels of protein, lipid and carbohydrates were formulated. Two sets of experiments were conducted with the following diet combinations: (1) 30, 30, 50% protein, 5, 10, 15% lipid and 0, 10, 20% carbohydrate and (2) 40, 45, 50% protein, 5% lipid and 20, 25, 30% carbohydrate. Protein and energy ratios ranged from 89-198 mg protein/Kcal while the energy values for all diets were 165-415 Kcal/100 g. The diets were given twice daily at 10% of the body weight. Results showed that a two- to three-fold increase was observed in the body weight of prawns fed with diet combinations of 40-50% protein, 5-10% lipid and 20% carbohydrate with energy values of 285-370 Kcal/100 g. Reduction in protein content of the diet from 50 to 40% while maintaining the total energy level (285 Kcal/100 g) resulted in a change in growth that was not significant. An increase in energy level, at constant dietary protein level, resulted in improved utilization of protein and feed conversion efficiency.

Adult tiger prawns Penaeus esculentus were held in laboratory tanks under varying conditions of tank size, density, temperature and photoperiod for assessment of ovarian maturation and spawning. Both eyestalk ablated and intact females were studied. Maturation and spawning of intact females was favored by conditions of warm temperature (26°C) and long days (14.5 hr), whereas ovary maturation did not occur at lower temperature (20°C) and short days (12 hr). Tank size was a critical factor with intact females as maturation and spawning required a large tank (4 m2). Spawning did not occur in small tanks (1 m2) despite ideal temperature and photoperiod conditions. Unilaterally ablated females matured and spawned under both short day-cold temperature conditions and in small tanks, but the success rate was greater under long day-warm temperature conditions in large tanks. Intact females required 40-60 days before onset of ovary maturation, whereas ablated females showed maturation to ovary stage III approximately 20 days after ablation. Mating success was severely limited under small tank conditions but occurred normally in the large tanks.

The cultivation of the microalga Tetraselmis chuii with the protection of the extracellular products of Chlorella kessleri, grown in a bialgal culture, allows its development in outdoor tanks without special conditions of sterilization or aeration. Fish meal and agricultural inorganic compounds are used as fertilizers. The growth of the mixed species is analyzed comparing it with monoalgal cultures. The best fit of growth data to a logistic curve is performed and the whole curve is compared using a covariance analysis. The stratification of T. chuii in the tank favors its harvest at high concentration. A bialgal culture (based on T. chuii at 50 cells/mm3) as food for the larvae of the shrimps Penaeus notialis and P. schmitti, together with hard boiled egg yolk and rotifers, achieves good development and survival.

Penaeus monodon juveniles (initial mean weight=0.62 g) were fed semi-purified diets containing 10, 20 and 30% trehalose, sucrose or glucose for eight weeks. Results showed that shrimps fed 20% trehalose gave the highest growth rate. Of the three types of sugars tested, trehalose promoted the best growth rates, followed by sucrose and glucose. When the level of sugar was considered, 20% gave the best growth rate and 30%, the lowest. The type as well as level of sugar greatly affected the body crude protein and body lipid (P < 0.01), while survival was mainly affected by type of sugar alone (P < 0.01). Trehalose and sucrose diets promoted better survival than glucose diets. A negative linear correlation (r = —0.70) between the body crude protein and body lipid was obtained.

The need for a nursery phase between the hatchery and the growing pond to avoid mortalities of young postlarvae, and provide a better assessment of stocked animals is general in crustacean aquaculture. The Centre Oceanologique du Pacifique recently developed a new culture technique using strong aeration, no water exchange and no external filter or artificial substrates. The technique relies on the development of a phytoplankton and bacterial medium with both nutritive and purifying qualities. Early postlarvae (PL3) are grown for a month or less up to 0.1 g mean weight, in 10 to 100 m3 tanks, at densities of 1 to 10 individuals/ℓ. The mean daily growth rates are around 20% for Penaeus indicus, P. stylirostris and P. vannamei and only 12-15% for P. monodon. For all species tested, density has little or no influence on growth. The final survival rates are generally high.

Saccharomyces cerevasiae and Rhodotorula aurantica, two marine yeast species, were fed to Penaeus monodon larvae (N6 to M1) singly and in combination with Tetraselmis sp. and Chaetoceros calcitrans in varying proportions. Larvae fed combination diets gave survival rates comparable to or higher than those fed algae or yeast alone. Chemical analyses show that the yeasts have low fat, moderate protein and high carbohydrate content. They also contain essential amino acids but are different in the fatty acids found to be essential for prawns. When used in combination with algae, the nutritional value of the yeasts seemed to have been improved. The use of marine yeasts in larval rearing could reduce economic and technological inputs in the production of natural foods for larval rearing. They are cheaper and easier to mass produce. They can be grown to very high densities using cheap carbon sources like molasses, brown sugar and coconut water with added nutrients in relatively shorter periods of time.