Milkfish (Chanos canos) and tilapia (Oreochromis mossambicus) were exposed to varying concentrations of rotenone (95-98% active ingredient) to determine the median lethal concentration (LC⁵⁰). The 1, 6, 12, 24, and 96 h LC⁵⁰ were 64, 36, 36, 30 and 25µg/1 for milkfish and 172, 123, 91, 86 and 80 µg/1 for tilapia, respectivly, at 28±1^oC. In another experiment, O. mossambicus were exposed to a lethal concemtration of rotenone (100µg/1) that had been allowed to age for selected periods of time to determine whether significant degradation occurs within 24h. Mortality after 3 to 24 h exposure in 0 (no aging), 3 and 6 h aged rotenone solution were not significantly different from the control test even after 24 h of exposure. These results inducate that the treated water was no longer toxic to the fish after 12 h and acute toxicity of rotenone ceased towards the end of 12 h at 27 ± 1^oC

The study was conducted to determine the effectiveness of a practical diet, the profitability of feeding during 2 seasons, and the effect of a diet with coconut oil on the fatty acid profile of milkfish (Chanos chanos ) fingerlings. Milkfish fingerlings of average weight 6.2 g and 10.2 g were reared in earthen ponds of 3 compartments (550, 1,100 and 2,200 m super(2)) using the modular culture system. One month prior to harvest, fish in Treatment 1 were fed a practical diet containing 42% crude protein, 13.1% crude fat and 33.2% nitrogen-free extract while fish in Treatment 2 depended solely on the natural food in the pond. The fish fed during the last month of culture were heavier (141 g) than the unfed fish (100 g) in Experiment 1 (dry season) but had similar weights (44 and 41 g) in Experiment 2 (rainy season). Weight gain of fish in Experiment 1 was significantly higher than in Experiment 2. Varying temperature and salinity during different seasons influenced fish growth and production. Feeding milkfish was not profitable during the cooler months. Fatty acid profile in depot fat of fed fish reflected that of the diet. Palatability tests showed that fed fish were preferred to the unfed fish.

Transport of live fish is a routine activity in aquaculture. Various transport techniques have been reported by Berka. Transport of grouper eggs (Epinephelus suillus) between fisheries stations in Thailand is being conducted. However, no report has been made on transport of yolk-sac larvae of this fish. In the Philippines transport of eggs poses difficulties, particularly for hatcheries which are distant from the broodstock rearing site since spawning occurs between 1600 and 1800 h. Eggs can only be collected the following morning and hatching starts around 1200-1300 h (20 h after fertilization). Thus it seems advisable to transport yolk-sac larvae rather than eggs of grouper under such conditions. This study was conducted to determine the feasibility and optimum loading density of transporting grouper yolk-sac larvae for about 2 h.

The development of an appropriate hatchery culture-technique for grouper Epinephelus malabaricus requires knowledge on the biology of this species. The environmental requirements, a critical aspect of biology, have, however, not yet been investigated. This study specifically deals with the influence of salinity on the survival of newly-hatched larvae.

Highly variable results using Brachionus as food for milkfish (Chanos chanos) larvae may be related to: (1) relatively low content of highly unsaturated fatty acids (HUFAs) in Brachionus and (2) inability of first feeding larvae (day 2) to ingest rotifers in sufficient numbers. Early supplemental feeding with a microbound diet high in HUFAs may improve growth and survival of milkfish larvae.

Growth and survival of Oreochromis niloticus, O. mossambicus, and their F₁ hybrids were studied at various salinities (0-32 ppt) in net cages inside 12-tonne concrete tanks after acclimation. Growth, measured as weight gain, and survival were assessed after three months of culture. Results showed that although O. niloticus, O. mossambicus, and their F₁ hybrids can be acclimated and grown at varying salinities, optimum salinity ranges for good growth varied greatly. The salinity ranges for good growth of O. mossambicus and F₁ hybrids were wider than O. niloticus. O. mossambicus had the highest growth rates at 15 and 32 ppt. The optimum salinity range for growth of F₁ hybrids was 15-32 ppt, while for O. niloticus it was 0-10 ppt. Salinity up to 20 ppt had no significant effect (P>0.05) on survival of all test strains. However, at 25-32 ppt survival of O. niloticus was significantly lower (P<0.05) than that of O. mossambicus and the F₁ hybrids.

Marine shrimps absorb minerals from their aquatic environment aside from the minerals that come from the food they eat. Thus, the dietary requirement of shrimps for certain minerals will depend on the amounts and availability of these minerals in the aquatic environment. Dietary sources for growth may be necessary due to losses during moltings. Most of the dietary studies for mineral requirements have been done under laboratory conditions with purified or semi-purified diets and hardly any information is available under practical culture conditions. Most published data for mineral requirements are for juvenile Penaeus japonicus. There are few data for P. monodon, P. californiensis, P. merguiensis, P. aztecus. Calcium and phosphorus are the minerals that have been studied the most. These two have been found to be related to problems of soft-shelling in P. monodon. Apparently calcium and phosphorus requirements are within the range of 1 to 2%. The ratio of calcium to phosphorus in the diet is also an important factor in the efficient utilization of both minerals. It seems that a 1 :1 ratio provides for good growth. Phosphorus deficiency results in reduced growth while lack of magnesium brings about decreased growth, poor survival and reduced feed efficiency in P. japonicus. Iron toxicity has also been observed in P. japonicus. It might not be necessary to include some minerals in the diet of penaeids.

Commercially important tropical freshwater and marine finfishes are commonly spawned with pituitary homogenate, human chorionic gonadotropin (HCG) and semi-purified fish gonadotropins. These preparations are often administered in two doses, a lower priming dose followed a few hours later by a higher resolving dose. Interval between the first and second injections may vary from 3 - 24 hours depending on the species. Variable doses are used even for the same species and may be due to variable potencies of the gonadotropin preparations. Synthetic analogues of luteinizing hormone-releasing hormone (LHRHa) are becoming widely used for inducing ovulation and spawning in a variety of teleosts. For marine species such as milkfish, mullet, sea bass, and rabbitfish, a single LHRHa injection or pellet implant appears to be effective. Multiple spawnings of sea bass have also been obtained following a single injection or pellet implant of a high dose of LHRHa. In a number of freshwater fishes such as the cyprinids, LHRHa alone however has limited efficacy. Standardized methods using LHRHa together with the dopamine antagonists pimozide, domperidone and reserpine have been developed for various species of carps. The technique may also be applicable for spawning marine teleosts that may not respond to LHRHa alone or where a high dose of the peptide is required. Although natural spawning is the preferred method for breeding cultivated fish, induced spawning may be necessary to control timing and synchrony of egg production for practical reasons.

Milkfish (Chanos chanos Forskal) is one of the most important food fish species in the world. In Indonesia, Taiwan and the Philippines, more than a quarter of a million tonnes of milkfish are harvested annually in brackish ponds, contributing roughly 60% of the total fish production from aquaculture in Southeast Asia. This tremendous level of production from a single fish commodity is projected to further increase in the coming years to meet the dietary protein needs of an ever-growing population in Southeast Asia. To address vital research gaps afflicting the milkfish industry, research has correspondingly intensified over the past 15 years particularly in the Philippines, Taiwan and Hawaii. Results of such research projects have widespread application not only among Southeast Asian nations but also among many untapped areas in the Pacific, the Middle East, Africa and Central America where milkfish culture is feasible. A sound approach to initiate a milkfish aquaculture project is to have an adequate knowledge of the basic biology of this species. Several researchers have presented in great technical detail some of these biological aspects at numerous symposia (Juario et al., 1984, Lee, Gordon and Watanabe, 1986). This paper will therefore summarize in moderate detail some recent additional information on several aspects of milkfish biology: taxonomy, distribution, life history and habitat, food and feeding habits, growth, reproduction and tolerance to environmental conditions. Aside from increasing our understanding of milkfish, it is hoped that this short review will goad others to undertake further scientific research on many unknown aspects of the species, thus contributing to both the quality and the quantity of milkfish served on our dinner tables.

In the Philippines, the level of intensity of Chanos chanos culture is categorized into traditional and extensive management. Pond types for different culture systems, stocking practices, acclimation practices, water management, growout culture and harvesting are discussed. Fish pen culture and management are also briefly considered.