At least five wild-caught Penaeus monodon from various maturation stages (initially classified in vivo as 0, I, II, III, IV, V) were measured, weighed and dissected for histological and histochemical studies. The anterior and posterior parts of the thoracic and abdominal regions of the ovary were sampled and stained with Mallory trichrome, alcian blue-periodic acid-Schiff (AB-PAS) and Sudan black. Results showed that the ovary is composed of the ovarian wall and its extensions, zone of proliferation, follicle cell layer and oocytes. The proliferating cells are less than 10 µm, have thin rims of cytoplasm, and increase in size as maturation proceeds. Based on histology, the stages were finally classified into groups (1) previtellogenic (stage 0), (2) vitellogenic (stages I and II), (3) cortical rod (stages III and IV), and (4) spent (stage V). The previtellogenic group consists only of perinucleolar oocytes (46-72 µm) which are stained negatively with AB-PAS and Sudan black. Oocytes bigger than 55 µm are enveloped by a single layer of follicle cells. The vitellogenic group is composed mostly of yolky oocytes (121-211 µm) with the following cytoplasmic inclusions: small granules of glycoproteins, medium-size globules of lipoglycoproteins, and few large lipid droplets. The cortical rod group consists mostly of yolky oocytes (288-408 µm) with additional rod-like bodies which contain acid and basic mucopolysaccharides but no lipid. The presence of cortical rods is a characteristic feature of mature penaeid ovaries. The spent group is similar to the previtellogenic group but contains some yolky oocytes, thicker follicle cell layers, or irregularly shaped perinucleolar oocytes. Th GSI ranges of the four groups are 0.899-1.937, 3.099-7.598, 5.631-12.000 and 1.848-2.919, respectively.

The hepatopancreas is considered to be the central organ of metabolism in decapod Crustacea. It is a system of blind tubules consisting of four cell types. The E-cells at the summits of the tubules develop into R-cells (for resorption of nutrients), F-cells (for production of digestive enzymes) and B-cells (function unknown). The ultrastructure of Penaeus monodon R-cells changes largely after starvation and feeding different diets. B-cells show slight reactions, while F- and E-cells are rather constant. Thirteen day-starvation results in a large decrease of the cell size and in a significant reduction of all cell organelles. After seven days starvation and four days refeeding with various extreme diets, the R-cells develop completely different food-specific ultrastructures. A distinct proliferation of the endoplasmic reticulum is characteristic of protein diets. Large fat drops are the main feature after refeeding with cod liver oil. Sucrose feeding results in "empty" cells with only few organelles. The most diversified ultrastructure with fat droplets and a high amount of all cell organelles is obtained by feeding a mixed diet. The study indicates that R-cells are very sensitive to the application of different diets. They could be used as monitor cells for the nutritional value and the availability of a diet for prawns. Particularly poor or badly formulated feed could be detected early by electron microscopy. This method may be very helpful for the development of artificial prawn diets in aquaculture, especially if natural sources will be used as food components.

At present, most hatcheries depend on live food like diatoms, Chlorella, rotifer and brine shrimp to rear the larval stages of various penaeid species. Mass production of live feed requires much space (tanks) and labor, and is often affected by environmental conditions. The possibility of substituting live food with artificial diet for Penaeus indicus larvae was evaluated. Carrageenan micro-binded diet (C-MBD) was selected as test diet and its composition was modified from C-MBD designed for P. japonicus (about 45% protein). Larvae stocked at 100/ℓ and fed five times/day at 0.8 mg/larva/day had an average survival rate of 45% from Z1 to M1. Water temperature was 26.5-30.5°C and salinity 32-33 ppt. An average survival rate of 70.2% from M1 to PL1 was attained when the stocking density was 30/ℓ and feeding was three times/day at 0.3 mg/larva/day (water temperature 25.5-28.5°C, salinity 27-32 ppt). From PL1 to PL5 at stocking density of 20/ℓ with feeding rate of 0.3 mg/larva/day (fed 3 times a day), the average survival rate was 64.9% (water temperature 25.5-28.5% C, salinity 28-32 ppt). The results show that the present composition of C-MBD is highly effective for myses up to the early postlarval stages of P. indicus.

The experiment was conducted in fifteen 500-m2 brackishwater ponds to determine the response of Penaeus monodon juveniles fed with various artificial diets. Five treatments with three replicates each were: two commercial feeds containing 45% and 40% crude protein (treatments I and II), two experimental diets formulated to contain 35% crude protein (treatments III and IV) and control, without feeding (treatment V). Shrimp were fed twice daily at feeding rates based on shrimp consumption. Highest mean harvest weight was attained in treatment I (23.47 g) > III (19.25 g) > II (18.86 g) > IV (11.29 g) > V (9.27 g). Statistical analysis showed that differences in growth were significant at 5% probability level. However, growth in treatments I, II and III are comparable, also growth in treatments II, III and IV. Growth in treatments I, II, III and IV was significantly different from treatment V. Highest mean survival was attained in treatment III (91.82%) > I (88.93%) > II (86.95%) > IV (83.62%) V (82.62%). Statistical analysis showed no significant differences among treatments at 5% probability level. Projecting on a hectare basis, mean yield for each treatment was: I (628.37 kg) > II (496.35 kg) per crop in 120 days culture. Good yield was attributed to provision of formulated feeds, use of pumps in addition to tidal change for water exchange and control of predators, and pest eradication through proper pond preparation.

An unknown growth factor previously suspected in squid meal was found in the protein fraction of squid (Loligo vulgaris). It is clearly different from hydro-alcohol-soluble feed attractants that are also present in squid meal. This squid protein fraction (SPF) improves the growth of Penaeus japonicus juveniles when added either in a semi-purified or in a more complex mixed diet. This growth-promoting effect does not seem to be related to the amino acid composition of SPF. In order to obtain more information on its action, several levels (1.5 to 16.0%) of SPF were added to a mixed diet. The diets were isoproteic (59% D.M.), isolipidic (8.5% D.M.), supplemented with vitamins, cholesterol, glucosamine, etc. They were fed as wet pellets to 3 replicates of 15 shrimp; blue mussel was used as the control. The growth of shrimp increased with the SPF level and attained a plateau above 6%. Body weight was significantly higher than that of the control group at this level. RNA content and RNA:DNA ratio increased with the SPF level indicating that growth was improved more by hypertrophy than by hyperplasy of the cells. The hepatosomatic ratio remained unchanged. The assay of two digestive enzymes, proteases and amylases, showed no clear effect of SPF on protease or amylase activities. More experiments are needed to explain the effect of the unknown growth factor of SPF.

Total viable aerobic heterotrophic bacteria (THB) associated with egg, nauplius, zoea, mysis and postlarva of Penaeus indicus and seawater in a hatchery system were estimated for three years from 1981 to 1984. The bacterial population varied from 1.3 × 104 to 8.72 × l07/g in egg, 1.5 × 104 to 6.17 × 107/g in nauplius, 4 × 103 to 3.14 × 107/g in zoea, 1.35 × 106 to 1.25 × 108/g in mysis, 1.6 × 105 to 8.44 × 106/g in postlarva. Water contained a THB population of 1.2 X 105 to 2.8 × 108/100 ml. Species of Vibrio, Pseudomonas, Aeromonas, Acineto-bacter, Moraxella, members of the family Enterobac-teriaceae, Micrococcus, Bacillus, and Coryneform group were encountered. Gram-negative bacteria were found to be dominant in all stages and showed an increase from egg (81.3%) to postlarva (92.7%). However such an increase was not recorded in the respective water samples even though gram-negative bacteria were found to be dominant. Vibrio spp. were found in high numbers in postlarvae and it was to be increasing from egg (10.4%) to postlarva (80%). The number of larvae in culture pools gradually declined as the nauplii metamorphosed to postlarvae through zoea and mysis. In general, coincidence of higher percentage of Vibrio spp. and larval mortality was recorded. Physico-chemical factors such as salinity, temperature, pH, oxygen, inorganic phosphorus, organic phosphorus, inorganic nitrogen and organic nitrogen of water did not show much variation in the same set of pools. Relationship between the physico-chemical parameters, bacterial population and the number of larvae is discussed.

Nursing postlarvae of Penaeus merguiensis in the same tank as rearing always results in low survival rates, around 30%. One reason is that stocking density for P1 is too high for postlarvae grown to P20 size. Another reason may be that it is impossible to sufficiently clean a tank containing culture stock. In order to overcome the first constraint and to test whether the second is valid, rearing of nauplii to early postlarval stage was done in one tank, then early postlarvae were moved to another tank for nursing to P20. Rearing was done in rectangular, concrete tanks (5 m × 5 m × 2m) of 50 ton capacity, with an initial stocking density of 20-40 nauplii/ℓ. Chaetoceros sp. at a density of 3-4 × 104 cell/ml, or Tetraselmis sp. at 1-3 × 104 cell/ml were fed to zoea stage, then rotifer was given when the larvae metamorphosed to mysis stage. Within 8-10 days, when all of the larvae metamorphosed to postlarval stage, they were transferred to the nursing tank. Postlarval nursing was done in rectangular, concrete tanks with a capacity of 12 or 30 tons. The stocking rate was 12 postlarvae/ℓ in the 12-ton tanks and 8 postlarvae/ℓ in the 30-ton tanks. The early postlarvae were fed constantly with brine shrimp, and the older postlarvae were fed 4-5 times daily with squid meat. Fifty to seventy percent of seawater was exchanged, and siphoning of food remnants was done daily. The postlarvae grew to an intermediate size (1.0-2.5 cm total length) for stocking in grow-out ponds within 12 to 20 days. The results of rearing in 50-ton tanks with an initial stocking density of 20-25 postlarvae/ℓ, 25-30 postlarvae/ℓ and 30-40 postlarvae/ℓ produced survival rates of 74.3%, 63.6% and 47.6%, respectively. The survival rate for nursing in 12-ton tanks, with stocking density of 12 postlarvae/ℓ was 85.0% and for 30-ton tanks with stocking density of 8 postlarvae/ℓ was 61.7%. These results seem to indicate that the rearing and nursing of shrimp would be more efficient if carried out in separate tanks.

A partial unilateral ablation was carried out on immature females of the pink shrimp Penaeus notialis. They were maintained in 1,600 ℓ asbestos-cement tanks together with apparently mature males, not submitted to treatment, at a ratio of 2 females: 1 male. A quick development of the ovary was attained, which did not present significant differences in average diameter of the ovocytes in the anterior, median, and posterior lobes, and with similar histological characteristics to those described for naturally mature females. Viable spawnings were obtained three days after the treatment and onwards. The larvae obtained showed normal activity and development.

South Carolina has some 28,500 ha of impounded coastal wetlands. These impoundments are remnants of the rice culture industry of the 19th century and are now of interest for waterflow management and possibly aquaculture. The purpose of this study was to evaluate and compare the potential for extensive commercial culture of shrimp in salt-marsh impoundments with that for semi-intensive production of shrimp in highland ponds. A hypothetical farm consisting of four 8-ha impoundments or ponds was chosen as the basis for the analysis, and it was assumed that only one crop of shrimp could be produced per year. Two alternative strategies for stocking the impoundments were evaluated: option 1, stock by natural recruitment via tide gates; option 2, stock at low density (25,000/ha) with hatchery-reared postlarvae. Highland ponds were to be stocked at a density of 75,000 PL/ha with hatchery-reared animals. Major fixed costs other than land purchase were considered, including renovation of existing impoundments by cross-diking to form 8-ha units and addition of extra tide gates. Estimates of annual and variable costs for postlarvae (where applicable), feed, labor, chemicals, pumping, supplies, vehicle use, mowing, interest, overhead, and miscellaneous items were also included in the analysis. Results indicated that extensive shrimp culture in salt water impoundments is likely to be a break-even or profitable activity for production levels of 90 kg whole shrimp/ha for stocking option 1, while option 2 would require yields of ≥225 kg/ha. In comparison, semi-intensive culture in highland ponds is likely to be successful if yields of ≥ 800 kg/ha are obtained. This preliminary analysis suggests that both extensive and semi-intensive culture of shrimp may be economically feasible in South Carolina, but this potential is as yet un-proven and shrimp aquaculture must be considered a high risk venture in this area.

Incubation of Penaeus monodon eggs and rearing of different larval stages were undertaken at nine temperature-salinity combinations. The eggs, nauplii, zoea and mysis from one spawner kept as stock culture at ambient temperatures of 26-30°C and salinity of 32-33 ppt were exposed to temperature levels of 23, 28 and 33°C and salinity levels of 23, 28 and 33 ppt. Eggs and nauplii survived the sudden change of temperature and salinity (from ambient to experimental) but the zoea and mysis did not. However, salinities of 23 and 28 ppt in combination with any of the temperature levels produced weak larvae. Highest mean hatching rate was obtained at the temperature-salinity combination of 23°C-33 ppt, followed by 28°C-33 ppt and 33°C-33 ppt. Incubation periods for these treatments were 22, 16 and 14 hr, respectively. Survival rate of nauplius (taken from stock cultures) to first zoeal stage was highest at 28°C-33 ppt, followed by 33°C-33 ppt and 23°C-33 ppt with molting time of 50, 45 and 75 hr, respectively. The nauplii exposed to 33°C-33 ppt molted to zoea stage within 38 to 40 hr but later died. Those exposed to 23°C-33 ppt and 28°C-33 ppt reached zoea stage within 57 to 60 hr and 48 to 50 hr, respectively. Similarly, the nauplii taken from the stock cultures and reared until postlarval stage (P1) under experimental conditions completed the zoea and mysis stages in 9 to 11 days at 28°C C-33 ppt, 7 to 9 days at 33°C-33 ppt, and 13 to 15 days at 23°C-33 ppt. Statistical analysis showed that salinity had highly significant effect on rates of hatching of eggs and survival from nauplius to first zoeal stage but not temperature although the latter had an apparent effect. However, both factors affected time of hatching of eggs and time of molting from nauplius to zoea. Interaction effect was significant only on rate and time of hatching. Different sources (spawners) of eggs and nauplii did not have significant effect on time of hatching and molting from nauplius to zoea, but significantly affected the hatching rate of eggs and survival rate of nauplii to zoea stage.