The gonadosomatic index (GSI) and the hepatosomatic index (HSI) were determined for wild-caught, eyestalk ablated Penaeus monodon at 5 reproductive stages (I to V). Tissues of the muscle, ovary and hepatopancreas in each stage were analyzed for crude protein and amino acid composition. Results showed that the GSI increased from stage I (immature) to IV (fully mature) but declined at stage V (spent) while the HSI did not change significantly (P less than or equal to 0.05). Muscle protein content did not vary markedly from stage I to V except for a slight lowering at stage III (late maturing). Ovarian protein increased from stage I to IV and decreased at stage V while from stage II, the reverse was true for hepatopancreas. Generally, few significant differences in amino acid content were found. Glutamic acid content significantly differed among stages in all three tissues. In addition, phenylalanine in the muscle, histidine and lysine in the ovary and arginine and luecine in the hepatopancreas differed among stages. The muscle had slightly higher arginine and gluatmic acid contents than the ovary and hepatopancreas but was lower in threonine and valine. The ovary had the lowest glycine content. Results showed similar amino acid levels among tissues and maturation stages, suggesting that amino acids are fixed and not affected by much variation.

The effects of different types of feed, given singly or in combination, on the growth and survival of bighead carp, Arislichlhys nobilis Richardson, larvae reared for a period of 12 weeks were determined. Growth was highest for fish fed with the combination of Moina and artificial feed followed by fish fed with artificial feed alone. Significantly lower (P < 0.05) growth was found in fish fed with green water +Moina+ artificial feed; green water + artificial feed; green water +Moina and Moina alone, in a descending order. Carp larvae reared in green water alone did not survive after the fifth day of feeding. Specific growth rales ranging from 0.59% day−1 to 2.75% day−1 were exhibited by fish in all the remaining six treatments. Although green water alone did not support the growth of the larvae, enhanced survival rates were observed when green water was given in combination with other feeds. Survival rate was highest in fish fed with the combination of green water, Moina and artificial feed, but was not significantly different (P > 0.01) from those given Moina+ artificial feed. Consequently, normalized biomass index was significantly high (P < 0.05) in fish fed with the combination of green water, Moina and artificial feed.

Asian seabass (Lates calcarifer) larvae were fed Brachionus cultured on Chlorella and, as soon as ingestin was possible, different types of Artemia, i.e., nauplii of the San Francisco Bay (SFB) strain, Great Salt Lake (GSL) strain or GSL nauplii that had been bioencapsulated with an emulsion containing high levels of the ω3-HUFAs (highly unsaturated fatty acids) 20:5 and 22:6. San Francisco Bay Artemia with a good natural fatty acid profile and small body size could be offered earlier than the larger but HUFA-poor Great Salt Lake strain. The poor nutritional quality of the latter, however, could be corrected by enriching the nauplii with an ω3-HUFA emulsion for 24 h, after which time high levels of the ω3-HUFAs 20:5 and 22:6 were obtained. When the Artemia diet offered before metamorphosis included natural or supplemented essential fatty acids, no significant differences in dry weight, length or survival of the fish were noticed, as compared to fish fed the naturally deficient GSL Artemia. Onset of metamorphosis and physiological condition after metamorphosis, however, were influenced by the HUFA content of the ingested prey. Seabass larvae fed SFB or enriched GSL Artemia started metamorphosis on day 19, while those in the non-enriched series never achieved metamorphosis and died of a nutritional deficiency syndrome by day 27. An indication of the physiological condition of the larvae and the early detection of the syndrome was possible by subjecting 21- and 25-day-old larvae to a stress test: abrupt exposure of the larvae to 65-ppt saline water resulted in abundant and early mortality in HUFA-deficient fish larvae. Fry receiving ω3-HUFA-fortified Artemia had a superior physiological condition which was reflected by significantly lower mortality figures in the stress test.

The effects of 24-h lighting on feeding, growth and survival of first-feeding larvae of Siganus guttatus were tested. Continuous light gave a higher mean survival (31.69%) with a maximum of 40.50% compared to natural daylight (17.10%). Larval size on day 7 also showed that continuous lighting gave improved results. Although feeding incidence increased with age of the larvae, a higher incident rate was observed for larvae held in continuous light from day 3.

The effect of storage temperature was evaluated on the basis of growth response of prawns fed for 10 weeks with diets stored at 0°C, 10°C, 28°C-31°C (ambient temperatures) and 40°C for a period of 10 weeks. Prawns were stocked at 15 pieces per 60-1 oval thank supplied with water at 28°C and 32 ppt in a flow-trough aerated system.There were five replicate tanks per treatment. Lowest weight gain (20 g) was observed for prawns fed the diet stored at 40°C and significantly higher growth response was observed as the storage temperature decreased (30.2g at 28-31°C; 37.7g at 0°C and 10°C). Body size was significantly (P<0.05) affected by diet after 6 weeks of feeding and highly significantly (P<0.01) after 8 weeks of culture.Peroxide values for diets exposed for 10 weeks to 28°-31°C (2.9 meq/kg). The highest survival rate (76%) and feed conversion (8.9%) were observed for prawns fed diets stored at low temperatures (0° or 10°C). Severe necrosis of the hepatopancreatic cells was observed in P. monodon fed with diet stored at the high temperature.

Monthly samples of sediment, water and commercially important species of fish, primarily Oreochromis niloticus and Chanos chanos , plus a few other species, were collected from the West Bay area of Laguna Lake, The Philippines from January to December 1987. Mercury levels were determined in all samples by cold vapor atomic absorption spectrophotometry. Results showed that sediment samples contained mercury levels ranging from 26.7 to 117 ppb. Mercury levels in water samples were low, ranging from below detectable to 0.5670 ppb. The mercury levels in the water were negatively correlated with conductivity and dissolved oxygen and positively correlated with turbidity. The mercury burden of the fish species samples was below the maximum permissible level set by the WHO and USFDA of 0.05 ppm. No direct correlation was observed between mercury levels in sediment and water, water and fish and sediment and fish.

A feeding experiment was conducted to determine the quantitative dietary requirement of milkfish juveniles for lysine. Milkfish (Chanoschanos Forsskal) of mean weight 5.92±0.14 g were fed diets containing 7.0, 11.0, 15.0, 19.0, 23.0 and 27.0 g lysine/kg dry diet for 12 weeks. The amino acid test diets contained white fish meal and zein supplemented with crystalline amino acids to provide an amino acid profile similar to milkfish proteins except for lysine. Each of the six diets was fed to four replicate groups of 25 fish in a completely randomized design and at a feeding rate of 5% of the fish body weight per day. On the basis of the growth response, lysinerequirement of juvenile milkfish was found to be 20 g/kg diet. This value corresponds to 4.0% when expressed as a percentage of the dietary protein. Survival (94–97%) was consistently high in all treatments. Except for loss of appetite resulting in low food intake and depressed growth, no nutritional deficiency signs were observed in fish given the lysine-deficient diets.

Milkfish grown on two natural foods were examined to determine the distribution pattern of the digestive lipases along the digestive tract and to identify the optimum condition for lipase activity. One food consisted of a biological complex of unicellular algae and diatoms (Food A) and the other consisted of fibrous filamentous green algae, predominantly Chaetomorpha brachygona (Food B). The major sites of lipase secretion in milkfish digestive tract were the intestines, pancreas and pyloric caeca. Lipase activity was somewhat higher for fish grown on Food A than those grown on Food B. Intestinal lipase activity was observed to be maximal at 45°C and at pH 6.8 and 8.0. Activity of pancreatic lipase was observed to be maximal at 50°C and at pH 6.4 and 8.6. The detection of two well-defined pH optima, one at slightly acidic and the other at alkaline pH for both the intestinal and pancreatic lipases suggests a physiological versatility for lipid digestion in milkfish.

This study was conducted to assess the effect of different levels of dietary intake and feeding frequencies on growth and survival of bigheadcarp, Aristichthys nobilis, fry. The feeding rates consisted of 10%, 20%, and 30% of body weight while feeding frequencies were one, three, and five times daily. Results showed that final weight, final length, and specific growth rate (SGR) differed in relation to feeding rate but not to feeding frequency. Highest values were obtained for fish on the 30% ration and fed once a day. A significant effect of higher feeding rate using lower feeding frequency on growth was manifested in final mean weight and SGR; increasing feeding rate resulted in increased growth. Feeding frequency significantly influenced fry survival with highest values observed when fry were fed once or three times per day. Highest survivals were achieved by fry on the 30% ration fed once daily. At higher feeding rates using lesser feeding frequencies better survival was noted. Survival rate had an inverse relationship to feeding frequency, but no overall relationship existed between feeding rate and survival rate. Both ration and feeding frequency significantly influenced normalized biomass index (NBI). Highest values were again obtained on the 30% ration and feeding once daily. Higher NBI values were observed with higher feeding rates at lower feeding frequencies. Increasing ration resulted in a corresponding increase in NBI.

Hormone-induction of spawning in bighead carp Aristichthys nobilis Rich. by single or double intraperitoneal injection with varying combined dosages of HCG and LHRH-A was conducted. Fish were spawned successfully following a single or double injection with 1800 to 2000 IU HCG in combination with 10, 15 or 20 µg HRLR-A per kg body weight. Fish injected with lower dosages of HGC at 1200 or 1500 IU/kg body weight plus 20 µg/kg LHRH-A did not differ significantly (P>0.05). Fish given a single injection ovulated after 12.0 ± 0.1 hours. No significant difference was found in the total number of eggs spawned per fish among the injection protocols (P>0.05). However, lower fertilization and hatching rates of eggs were observed in fish that spawned spontaneously in the tank as compared to those fish whose eggs were stripped and dry-fertilized (P<0.05).