The influence of various levels of kinetin on growth, carbohydrate, nitrogen, and protein content of Azolla pinnata var. imbricata plants cultured in a nitrogen-free 40% Hoagland’s solution under greenhouse conditions was investigated. Kinetin concentration of 0.10, 1.0 and 5.0 ppm significantly enhanced fresh matter yield during a two week period. The carbohydrate content increased in plants subjected to 0.10 and 1.0 ppm kinetin. The significant increase in the nitrogen and protein levels of whole plants grown in the presence of 0.01, 1.0 ppm kinetin would enhance its nutritive quality as fish feed. Kinetin at 10 ppm decreased yield as well as carbohydrate, nitrogen and protein content.

The effects of dietary leucaena leaf meal on reproductive performance and growth of Nile tilapia were determined. In the preliminary trial, sexually mature Nile tilapia were fed with a control diet or a test diet which had leucaena leaf meal as the only protein source for 24 weeks. Fish fed with the leucaena diet lost some weight and had significantly low (P<0.05) gonadosomatic index and fry production compared to those fed with the control diet. Subsequently, four isonitrogenous diets (20% crude protein) containing varying amounts of leucaena leaf meal (0, 20, 40 and 80%) were fed to Nile tilapia broodstock. Mean weight gain of the female fish decreased as the level of leucaena leaf meal in the diets increased. Females fed with the 80% leucaena diet invariably lost weight. Mean weight gain of males fed with the control diet and the 20 and 40% leucaena diets did not differ significantly (P>0.05). However, growth of males fed with the 80% leucaena diet was remarkably low. Fry production was highest for those fed with the control diet and the 20% leucaena diet. Fry production decreased slightly in fish fed with the 40% leucaena diet and was significantly low (P<0.05) for those fed with the 80% leucaena diet. The low fry production was preceded by a decrease in body weight of the female fish. However, the gonadosomatic indices of the females and the males were not markedly affected by the diets. On the basis of both fry production and growth, leucaena leaf meal should not exceed 40% of the diet of Nile tilapia broodstock.

The nutritional value of Artemia sp. as food for marine fish and crustacean larvae has been linked to the level of its polyunsaturated fatty acid (PUFA) content. Experiments in August 1984 were conducted to determine the effects of various artificial diets and algae on fatty acid composition of PUFA-deficient Artemia sp. (Utah GSL strain) and their resulting value as food for postlarvae of the prawn Penaeus monodon (Fabricius). Nauplii of the brine shrimp were grown on extracts of corn, copra, soybean and rice bran containing precursors (C18) to long-chain PUFA and also on algal species containing different levels of long-chain PUFA (C20). The nauplii were then used as food for P. monodon postlarvae. The results revealed that absence of C20 polyunsaturates from the feeds and their presence in the algae were reflected in the polyunsaturated fatty acid content of the tissues of Artemia sp. When fed with brine shrimp fed on algae, P. monodon displayed better postlarval survival and significantly higher growth; related to the content of polyunsaturated fatty acids in Artemia sp. A practical feeding approach in prawn hatcheries would be to grow Artemia sp. on a cheap diet such as rice bran, and then to enhance its nutritional value with a diet high in PUFA prior to harvesting, in order to improve hatchery production.

Nine experiments were conducted to investigate the influence of chronic administration of testosterone (T) and gonadotropin-releasing hormone (GnRH) analogues on first maturation of 4- to 6-year-old fish and rematuration of 6- to over 9-year-old spent/regressed fish. Implantation of T or T in combination with luteinizing hormone-releasing hormone analogue (LHRH-A) had no marked effect on maturation rate of 4-year-old milkfish. The percentage of maturing fish was low and similar to controls in Experiment 1 (T, 31–35%; control, 35%) and Experiment 3 (T, 13%; T plus LHRH-A, 28%; control, 22.2%). Most of the 4-year-old maturing fish were males; maturing females were obtained only from the T-implanted groups in Experiment 1. In Experiment 3, T-implanted maturing females were able to retain yolky eggs whereas maturing control females did not, indicating that testosterone may have enhanced vitellogenesis and maintained the integrity of vitellogenic oocytes. Tank-reared maturing 4-year-old females, about half the size of older first maturing females, were induced to spawn. This is the first case of maturation and spawning of 4-year-old milkfish reared in tanks. As in Experiments 1 and 3, the percentage maturation of spent fish in Experiments 7 and 8 was similar for T-implanted and controls. On the other hand, the 4-year-old immature fish in Experiments 2 and 4, the 5- and 6-year-old immature fish in Experiments 5 and 6, and the spent 6-year-old fish in Experiment 9 were immature or regressed throughout. The factors which may have influenced the results of these experiments include age and reproductive history of the fish, timing of hormone implantation, experimental and holding conditions, and stress.

The effects of Na-EDTA on growth and survival of Penaeus monodon larvae were determined for applications given daily or every 3 days. Application of 2.0, 5.0, and 10.0 ppm were given on day 1, day 4 and day 7 in Experiment 1, and 5.0 and 10.0 ppm were given daily for 8 days in Experiment 2. Larvae stocked at 100/liter were given a natural food diet of Chaetoceros calcitrans and Artemia salina nauplii. Chloramphenicol (2.0 ppm) and Treflan R (0.05–0.10 ppm) treatments were applied on the same days as Na-EDTA. Water change was 30% on day 4 and 50% daily thereafter. Results showed that the application of Na-EDTA at 5.0 and 10.0 ppm on days 1, 4 and 7 greatly improved the survival of P. monodon larvae. With daily application, the larvae treated with 10.0 ppm showed the best survival rate during the 8-day culture period. Na-EDTA treatments at dosages above 2.0 ppm seem to prevent significant mortality. It is believed that Na-EDTA improved survival rates by chelating toxic elements in the culture medium. Growth (rate of metamorphosis) was not greatly improved except for anuplii to zoea where the highest percent molts were observed with the 10.0 ppm treatment in both experiments.

Aeromonas hydrophila was consistently associated with necrotic ulcers and lesions in mudfish/snakehead (Ophiocephalus striatus), Thai catfish (Clarias batrachus), crucian carp (Carassius carassius) and goby (Glossogobius giurus) in Laguna de Bay, Philippines, during the months of December 1985 through February 1986. The bacterium was isolated from body lesions and ulcers of all fish examined and rarely from the kidney and liver of carp and catfish. The disease was characterized by hemorrhages, lesions and open necrotic ulcers on the body of the fish, particularly the head (just behind the eyes), the mandible and the maxilla, and the caudal peduncle regions. Erosion of the head bone tissues and the tails was observed in very severe cases. The presence of A. hydrophila is believed to be secondary to some predisposing factors existing in Laguna de Bay.

Milkfish, Chanos chanos, larvae were found to suffer 100% mortality within 6 days of feeding when reared on Chlorella sp. According to the liver ultrastructure, Chlorella-fed fish underwent starvation. Likewise, no signs of lipid absorption were observed in the intestine of Chlorella-fed larvae. On the other hand, Chlorella-related histological alterations of the enterocytes in the anterior part of the intestine were different from starvation-related alterations. It is concluded that Chlorella-feeding creates a starvation situation for larval milkfish, but the early losses with this diet are due to an additional stress specifically introduced by Chlorella-feeding.

Young Nile tilapia (12 mg mean body weight and 11 mm total length) were stocked at a density of 5 fish/l in twelve 50-l aquaria filled with 30 l of tap water. They were fed pellet crumbles containing 35% crude protein at various daily feeding rates expressed as percentages of fish biomass. Mean increases in body weight after 5 weeks were 63, 198, 232 and 228 mg for the 15, 30, 45 and 60% feeding rates, respectively, when ambient temperature ranged from 19 to 21°C. Corresponding survival rates were 53, 85, 87 and 84%. Growth and survival rates were enhanced significantly (P < 0.01) at the 30, 45 and 60% feeding rates. Two feeding trials were conducted to compare the growth and survival of fry fed pellet crumbles and an unpelleted form of the same diet. Results showed that growth and feed conversion were similar for both forms of diet. However, the survival rate of fry fed pellet crumbles was significantly higher (P < 0.01) than the survival rate of fry fed the unpelleted diet. Prior pelleting of the formulated diet for the tilapia fry given at 30% to 45% of fish biomass daily ensured high survival, fast growth and efficient feed conversion.

The osmotic and chloride regulation by 5- to 10-g intermolt Penaeus indicus was investigated by abruptly changing medium salinity from seawater (32 ppt) to test salinities of 8, 20, 32 (control) or 40 ppt. Hemolymph samples were taken at 0, and then at 0.25, 0.5, 1, 2, 5 and 10 days after the change in salinity, and were analyzed for osmolality and chloride concentrations. Tissue water content was also determined. Throughout the study period, daily mortality was low (1.8%), and was the same among control and experimental salinities. Hemolymph osmolality and chloride as well as tissue water content were stable within 0.25 to 0.5 days after the abrupt salinity change, except for tissue water content at 8 ppt which did not reach a steady state for 2 days. Intermolt P. indicus exhibited hyperosmotic or hyperionic regulation in salinities below isosmotic or isoionic salinities, and hypoosmotic or hypoionic regulation in those above. Hemolymph osmolality and chloride were positive linear functions of external osmolality and chloride concentrations (slope=0.24±0.02 and 0.20±0.02, respectively). Isosmotic and isoionic values were 780 mOsm/kg and 330 mM, respectively. Percentage tissue water decreased as a function of external osmolality (−0.0056% kg mOsm⁻¹) and hemolymph osmolality (−0.0232% kg mOsm⁻¹), indicating that tissue cells were relatively permeable to hemolymph water, and that the hemolymph acted as a barrier to buffer the cells from large fluctuations in external salinity. These results indicate that, like many penaeids, P. indicus is a good osmoregulator suitable for culture in brackishwater ponds where there are large fluctuations in salinity.

Sample of Penaus semisulcatus or Tiger Shrimp ("hipong bulik") from Manila Bay and Tayabas bay, and from waters off Palawan, Cebu, Samar and Capiz were obtained from Navotas Fishery Port during the period from March, 1978 to Febuary, 1979. The prevalence of Epipenaeon ingens in P. semisulcatus is 4.83/1000. No significant difference (P>0.05) in the prevelence of infection between the sezes was found. The parasites (E. ingens) was lodged on either side of the host's carapace and there was no significant difference in the regression analyses of the tumor size on carapace length wheter tumor is on the left or right side of the carapace of either male or female host. Despite the homogenity of regression lines in the comparative analyses of length-weight relationship of infected and uninfected P. semisulcatus, the slope of the regression of the infected sample are always higher than the value for the uninfected ones.