This study was undertaken to determine the activities of alkaline and acid type proteases [proteinases], α-amylase, lipase [triacylglycerol lipase], trypsin, chymotrypsin, leucine aminopeptidase [cytosol aminopeptidase], and alkaline and acid phosphatases during larval development of the grouper, Epinephelus coioides. The maximum variation in specific activities of alkaline and acid type proteases, α-amylase, lipase, trypsin, chymotrypsin, leucine aminopeptidase, and acid and alkaline phosphatases in the digestive tract of grouper larvae was mostly related to the onset or the end of metamorphosis during larval development.

The histomorphological changes in the gastrointestinal tract of Epinephelus coioides and associated organs during its early development were studied. Larvae of E. coioides were reared in 5-tonne tanks using the semi-intensive culture system. Larval samples were collected at days 0, 2, 4, 6, 8, 10, 12, 14, 16, 20, 25, 30, 35, 40, 45 and 60. The total length (TL) of about 10-20 larvae per sampling was measured. At least 3 samples were examined from each stage for longitudinal sections using light microscopy. The digestive tract of day 0 larvae was a straight, undifferentiated tube composed of simple cuboidal cells. At day 2, cellular differentiation was observed in the pharynx, oesophagus, primordial stomach and intestine. The primordial stomach broadened into a voluminous pouch at day 10. The gastric gland was observed in the stomach from day 20. Day 35 seemed to be the proper time to feed larvae with minced fish when using the semi-intensive rearing system. Insignificant histomorphological changes in the metamorphosing grouper larvae were observed from days 40-60.

Fingerling production of milkfish in ponds maybe operated as a commercial enterprise or a component of milkfish farming that comprises nursery, transition and rearing or grow-out phases. The fishpond nursery is used to grow milkfish fry to fingerlings 1-3 g in weight or 1-2 inches in length. The nursery pond is the smallest of the major fishpond compartment ranging from 500 to 5,000 m², and is about 10% of the total farming area. The pond is prepared with utmost care to eliminate predators and competitors. The area should have good topography, is free from flooding and should have soil with good water retention properties for good dike construction and efficient culture management. Water supply should be adequate year-round and free from pollutants. Good pond water quality is maintained and natural food should be adequate to enhance growth and survival. With high stocking densities, supplemental feed is also provided. The three types of nurseries are based on feed sources: lablab, plankton with supplemental feeding and direct feeding. Select hatchery-reared fry (21 day old) that swim actively in schools, are uniform in size, have robust body, and are resistant to handling and transport stress. The ideal fry stocking density is 5-40 pieces/m². Survival ranging from 50-90% can be expected after 25-45 days of rearing. Harvest, packing, transport, acclimation and stocking of the fry or fingerlings are carefully done during the cooler part of the day. Economic indicators show that fingerlings production is a profitable business. The improvement of milkfish grow-out technology from extensive or traditional to modified-extensive, semi-intensive and intensive culture in ponds, pens or in sea cages has increased demand for good quality fingerlings. Mass production of hatchery-reared fingerlings in earthen nursery ponds during peak season of fry availability can help bridge the supply gap. A steady supply of fingerlings for a whole year s operation will further increase production and ensure a sustainable supply of affordable market-sized fish.

Asian catfish Clarias macrocephalus is an esteemed food fish especially in Southeast Asia due to its tender and delicious meat. This commodity constitutes a valuable fishery for small-scale fishers in the region and has a great potential for aquaculture. The important considerations in the grow-out culture of catfish are reliable water supply, soil with good compaction properties for dike construction, supply of fingerlings, feeds, labor, pond supplies and technology assistance. The farm must also be accessible by road, near to market facilities and has a peaceful environment. Rearing catfish in ponds is the most popular and commonly practiced. The pen culture is a system fully enclosed by nets on all sides but utilizes the dug-out pond, dam or lake bed as bottom enclosure. Tanks in abandoned old hatcheries with freshwater source can be used for catfish culture. In the cage culture system the stock is fully enclosed by nylon nets on all sides and bottom similar to an inverted mosquito net installed in suitable areas like reservoirs, dams, lakes and dug-out ponds. The rice-fish (catfish) culture is also practiced where the rice pond canals are utilized to retain water at 1-2 m depth to provide shelter to the fish while the rice plot maintains 10-20 cm water depth. For the stock, select fingerlings that are active, healthy and uniform in size. Handling of fish stock is important to avoid mortality due to stress during harvest, sorting, counting and transport. Furthermore, stocking of fish is recommended during the cooler part of the day. Catfish fingerlings stocking density is about 5 to 20 pcs/m² depending on the water supply and support facilities of the farm. The catfish, C. macrocephalus, requires a substantial amount of dietary protein for growth. For this species a formulated diet with crude protein (CP) of 34%, moist diet (trash fish or blanched chicken entrails plus rice bran or cooked broken rice), and a combination of pellet feeds (50%) and moist diet (50%) have been tested and acceptable for the grow-out culture. Economic evaluation based on a grow-out culture in pond with an area of 1,000 m² showed that feeds and fingerlings are the major variable costs. The net income, return on investments and payback period, respectively range from PhP22,972-PhP35,741, 80-122% and 0.8-1.2 years when using pellet, moist feed or a combination of these feeds. Feeding using formulated diet has an advantage of convenience, quality and quantity over moist diet which has issues such as inconsistent supply, storage requirement and fouling the rearing water.

Preliminary findings from a spatfall forecasting programme initiated in April 1981 at Himamaylan River, Negros Occidental are presented. Two main activities are involved: 1) monitoring of daily counts of oyster larvae in the plankton; and 2) monitoring of actual setting of oysters on standardized collectors put in the vicinity of oyster farm sites. Findings indicate that when the count of mature larvae exceeds 5 per 100 ml sample and persists for at least 3 days, spat may be expected to occur shortly afterwards.

An experiment was undertaken in order to investigate the use of sago palm starch, gum arabic and carrageenans as binders in prawn diets. Water stability data are presented; EPT-2 carrageenan was found to be the best binder for both steamed and unsteamed pellets.

A study was conducted to determine the effects of single injections of human chorionic gonadotropin (HCG) and Durandron Forte 250 on sperm motility, vitality and density and also on the consistency of milt in newly caught, wild, mature milkfish (Chanos chanos). In contrast to HCG, single injections of Durandron Forte 250 were effective not only in inducing spermiation but also in maintaining newly caught mature males in good running condition for a maximum of 7 days, despite daily handling and collection of approximately 3ml milt.

Penaeus monodon juveniles were reared on semipurified diets containing various carbohydrates (maltose, sucrose, dextrin, molasses, cassava starch, corn starch or sago palm starch). Significant differences were observed between the type as well as the level of carbohydrate in the diet on the survival of the juveniles. Results indicate that there does not seem to be any correlation between survival and the complexity of the carbohydrates.

Histopathological effects of ammonia on the gills of milkfish (Chanos chanos) fingerlings were examined qualitatively.