The most important criterion among many used by operators for choosing poostlarvae to stock in ponvds, is the stage of development. THe stages considered suitable for stocking (about PL₂₀) can be identified by examination of anatomical features including the rostal spine number, the length of carapace and sixth abdominal segment. Pigmentation in uropods, size uniformity and activity of post larvae are useful considerations. During Transport,decreasing water temperature to lwer metabolic rate helps ensure the adequacy of oxygen in bags. Upon stocking, acclimation to the temperature and salinity of pond water is very importan. If changes are sudden, regulatory mechanisms may fail, resulting in moralities.

An ion chromatographic method of separating and detecting nitrite in sea water is described. The system includes precolumn, new hydrophilic separation column, suppressor and two-valve system. Nitrite was diverted, trapped and separeted in a 2.6-ml sample loop using 6- and 4-port valves. The eluent used was 14.4 mM sodium hydrogen carbonate at flow-rate oflml/min while the scanvenger was 14 mM sulfuric acid. Nitrite recovery achieved was 100±2%. The minimum detection limit was 0.15 ppm with the signal-to-noise set 2.5 Nitrite recovery obtained using different mixing ratios of sodium hydrogen carbonate and sodium carbonate were lower. Eluent ph and compoosition affected both peak heights and retention timed of nitrite and other anions.

Disease management of intensively-cultured prawns requires an understanding of physiology and disease causation. Maladies result from an interaction of the prawn, disease agents and their environment. In intensive culture, the environment becomes increasingly difficult to control. Hence, surveillance for the early signs of disease, potential pathogens and the development of adverse environmental conditions should be integral components of a sound management system.

A major factor that influeces the success of production in the prawn industry is the occurrence of disease. Early stage of prawn in hatchery-nursery systems are subject to attacks of viruses, bacteria, fungi and protozoan pathogens. Although these microbial disease agents may also invade prawn juveniles and adults, nutrition and environmental diseases appear to play more important roles in grow-out ponds. Control of diseases involves correct diagnosis, prevetion and treatment. Rigid sanitay practices in hatchery followed by effective management through dietary and environmental manipulation in grow-out ponds are highly recommended.

Diseases of prawn in ponds are caused by microorganisn like viruses, bacteria fungi and protozoans as well as factors such as nutritional deficiency, poor pond conditions and environmental pollutants. Most of these may be controlled by environmental and dietary manipulation. Control of transfers or introduction of new prawn species may also reduce the risk of disease occurrence. Chemotherapy is considered only as alast resort in the control of diseases in prawn ponds. The basic features of prawn diseases with emphasis on causative agents and methods of preventio and treatment are discussed.

A study was conducted to evaluate the effectiveness of luteinising-hormone releasing hormones in the induction of spawning of Lates calcarifer using different administration techniques: pellet implantation, Chinese analogue and osmotic pump implantation.

In spite of the economic importance of milkfish to the Southeast Asia, relatively little information is available on its reproductive biology and physiology. Milkfish has a prolonged juvenile phase undergoes first sexual maturation at five years. Steroid hormone profiles during this juvenile phase and the change accompanying sexual maturation is described. There were no significant differences in levels of serum estradiol 17-B (E2), testoterone (T) and progestrone (P) of male and female immature fish. In immature fish, E2 ranfed from 0.145 to 0.600 ng/ml, T varied from 2.04 to 3.75 ng/ml, and P ranged from 0.472 to 1.16 ng/ml. Serum T, however, was significantly high in 4 years old immature fish fish while E2 was significantly high in 2 years old fish. Mean E2 level rose from 0.54 ± 0.11 ng/ml (E2) in immature female (Stage 1) to 4.53 ± 1.16 ng/ml in vitellogenic females (Stage 5) while T increased from 2.06± 0.28 ng/ml to 38.4± 9.26 ng/ml. E2 and T levels were positively correlated to egg diameter. Progesterone level, however, remained low through vitellogenesis. 17-a-OH-progesterone and 17-a, 20-B-progesterone were not detectable even in fully vitellogenic females. Gonade development in males was sccompanied by increase serum T levels only. T levels increase from 2.5± 0.40 ng/ml in immature males to 27.73± 5.02 ng/ml in spermeating males. Significantly higher T level was found in males with thick but abundant milt (spermiation index, SPI, 2+ ) compared to males with scanty milt (SPI, 1+) or mals with copious, fluid milt (SPI, 3+). Ther was no significant seasonal variation in levels of E2 and T of immuture 3-5 years old female sampled from july 1981 through February 19083. Serum E2 varied from 0.125 ng/ml to 1.45 ng/ml while T was uniformly low and ranged from 1.16 ng/ml tp 2.07 ng/ml. The levels of E2 and T significantly rose during the breeding season (April-June, 1983)and accompanied the increase in gonadosomatic index (GSI) aat this time (E2, 3.43± 0.49 ng/ml; T, 40.04± 16.20 ng/ml ). The levels of both steroids dropped to below 1 ng/ml in spent females sampled in the succeeding months. In immature males, mean serum E2 was beolw 1 ng/ml through except for a significan high level (2.36 ng/ml ) found in 3 years old male sampled in October to December, 1981 while T levels ranged from 1.11 ng/ml to 2.78 ng/ml. As in females, T levels significantly rose to 21.52± 8.38 ng/ml during the breding season when GSI peaked (April-June ,1983). E2 remained low throughout. T level dropped to arround 10 ng/ml in the succeeding months when spent or regressed fish were samlped

The physicochemical and biological parameters of an integrated flow-through poultry-salt-Artemia-milkfish-sea bass-shrimp pond production system were monitored for 6 months to determine the pattern of nutrient changes and associated plankton communities as water passed through the system. A 20 ha salt farm in Negros Oriental, Philippines, was used as a model of the integrated system. The construction of a poultry farm at the inlet reservoir provides continuous fertilization and allows considerable control of nutrient inputs to the pond system. Nutrients increase markedly in the chicken pond and in subsequent ponds undergo cycles of biological assimilation and bacterial mineralization. Principal component analysis ordinates temporal and spatial changes in 33 variables that were monitored. Using scatter diagrams of the principal components enabled separation of ponds adjacent to the crystallization bed and ponds high in fish biomass from the rest of the system. Variables that served to numerically delineate the ponds in this manner were salinity, phosphate, ammonia, alkalinity, turbidity, acidity, microplants, pico- and nannoplankton. The implications of this ordination in relation to pond management techniques is discussed.

The successful and profitable production of Tilapia nilotica in ponds or cages is predominantly influenced by the environment and hereditary traits of the stock. Therefore, stocking of high quality fingerlings is a major requirement to ensure the profitable production of marketable tilapia in 90-120 days. There are reports on crossbreds of F₁ backcross of two strains of T. nilotica stocked in net cages in the central bay of Laguna Lake at 15/m² during the months of May to August, reach a marketable size of 100 to 180 grams in 70 days without supplemental feeding. It is not uncommon for tilapia farmers in Cardona, Tanay and Pililla, Rizal to harvest marketable outbred tilapia after three to four culture months from May to August. In the case of F₃ inbreds of T. nilotica, stocks that have a certain degree of T. mossambica blood, growth is comparatively slower.

Wild Penaeus notialis and P. schmitti were induced to mature by unilateral eyestalk ablation of females in 0.5, 1.6 and 2.0-m super(3) tanks stocked at 9-12 shrimps/m super(3). A total of 71 spawns was obtained from 80 P. notialis) females in 2 experiments and 29 spawns from 72 P. schmitti females in 3 experiments over 16-19 days per experiment. Average fecundity and hatch rate were 44,410-64,997 eggs/spawn and 0-71.70% for P. notialis and 41,672-48,083 eggs/spawn and 0-0.17% for P. schmitti , respectively. The low hatch rates throughout the experiment period for P. schmitti , an open thelycum species, and towards the second week for the closed thelycum P. notialis , indicate a failure of spermatophore transfer in the maturation tanks. This lack of copulation may be traced to the high stocking densities and the small sizes of the tanks. Attempts to artificially transfer spermatophores to mature P. schmitti females were generally unsuccessful.