Several milkfish (Chanos chanos) juveniles polycultured with the Indian prawn (Penaeus indicus) in earthen ponds at the Leganes Station of the Aquaculture Department, SEAFDEC, Philippines, manifested eye abnormalities. Signs observed varied from unilateral and bilateral opaque eye coverings/eye balls, exophthalmia and hemorrhagic eyes. A vibrio was predominantly isolated from the opaque eye coverings and eye balls, and it was proved pathogenic to milkfish, Japanese eel (Anguilla japonica) and mouse by injection experiments. The opaqueness of eye coverings of milkfish was likewise reproduced by a combination of injury and contact with the pathogen. The bacterium, though seemingly closely related to Vibrio parahaemolyticus or V. alginolyticus, was not identified to any known Vibrio species.

Phytoplankton cultures of Chlorella sp., Tetraselmis sp. and Isochrysis galbana were used alone as feed to rear separate batches of newly caught milkfish (Chanos chanos) fry (about 21 days old). Ultrastructural studies of fry hepatocytes and pancreatic acinar cells indicated that they cannot directly utilize Chlorella, which has a rigid cell wall. The fry can directly utilize Tetraselmis and Isochrysis, but neither is nutritionally adequate for growth and survival if used as the only feed. Tetraselmis is nutritionally inferior to Isochrysis.

1. Morphological properties of fish intestines vary with diet. Carnivores have short guts with highly elaborate mucosal folding in the upper intestines; herbivores have long guts which appear structurally uniform from stomach to rectum. 2. Brush border membranes of many fish intestines display at least two transport processes for each organic solute, one an Na+-dependent, saturable carrier mechanism, and the other a non-saturable influx pathway which may be simple diffusion. 3. Intestinal epithelial cells from freshwater fish can accumulate nutrients to concentrations in excess of those in the gut lumen; those of marine fish can not. 4. Net transepithelial nutrient transport in upper intestine is greater in freshwater fish than in marine forms as a result of considerable solute backflux from epithelium to lumen in the latter. 5. In many fish the lower intestine displays a significant net transmural flux of nutrients that may contribute to total organic solute absorption. 6. Intestines of freshwater fish have a serosa positive (relative to mucosa) electrical potential difference; marine fish display a negative serosa. 7. Addition of organic solutes to intestines of freshwater fish hyperpolarizes the electrically positive serosa; in marine forms a depolarization of the serosa negative potential occurs. In both cases this appears due to increased net transmural sodium transport coupled to net nutrient flow.

Samples of Oreochromis niloticus and Tilapia zillii were collected from the hatcheries of Osaka Prefecture Fisheries Experimental Station and Shiga Prefecture Fisheries Experimental Station, Japan, respectively. The samples were used for screening polymorphisms in 13 enzymes, skeletal muscle proteins and hemoglobins by horizontal starch gel electrophoresis. Among 35 loci examined, 12 loci for the 10 enzymes, sarcoplasmic protein and hemoglobins were polymorphic in O. niloticus and 2 loci for 2 enzymes were polymorphic in T. zillii. The observed numbers of phenotypes for respective loci agreed well with Hardy-Weinberg expectations. The genetic basis for each polymorphism is discussed. This investigation provides basis information on the status of these tilapias in Japan.

A spatfall forecasting program in April-November 1981 suggests that daily counts of larvae in plankton samples may be used to forecast spatfall of C. iredalei . Counts of at least five ready-to-settle larvae per 100-liter sample for three to five days indicate that spatfall will occur very soon and that collector materials should be put out immediately. Oyster spatfall was good in the months of July, August, and September. Highest larval count was 247 ready-to-settle larvae per 100-liter plankton sample; this led to a record set of 2,423 oyster spat on a string of thirteen shell cultch between August 24 and 31.

Effects of three temperature treatments on activity, feeding, growth, development and survival of young milkfish (Chanos chanos) were investigated. Low temperature (<22.6°C) and hypoxial condition (<1 ppm O2) decreased activity, responsiveness and food intake; high temperature (up to 33°C) had the opposite effect. Growth and development were fastest in fish maintained in high temperature (x = 29.5°C). Fish in low temperature (x = 20.7°C) had the least growth and were inhibited from developing into juveniles during the 3-month period. Highest survival (x = 99.7%) was obtained in high temperature but was not significantly different (P>0.05) from ambient temperature (x = 97.7%).

Wild milkfish fry (mean weight = 15 mg) were reared in fresh water for 5 weeks using four artificial dry diets, Moina, or blended water hyacinth leaves as feed. The fry fed with artificial diets attained 83–95% mean survival rates and 0.16–0.18 g mean weight gains. Those fed with Moina and blended water hyacinth leaves had much lower growth and survival. The four dry diets containing 40% crude protein appeared adequate for the fry. Substitution of up to 5% crude protein by soybean meal and/or ipil-ipil leaf meal did not affect growth, but diets containing ipil-ipil leaf meal gave slightly lower survival rates.

Effects of thyroxine (T₄) (0.1 ppm; 0.3 ppm; 0.5 ppm) on Sarotherodon niloticus L. yolk sac larvae were studied after 4 weeks of treatment from hatching. T₄ at 0.5 ppm accelerated yolk resorption but did not significantly increase growth after the first week of treatment. Increase in length and in weight among fry treated with T₄ at 0.1 ppm and 0.3 ppm was significant after the fourth week. T₄ at 0.1 ppm increased significantly the length of the pectoral fin; but at 0.3 ppm and 0.5 ppm caused abnormal shapes in the pectoral fins as well as lordosis and scoliosis. T₄ reduced pigmentation in treated yolk sac larvae for 3 days only and caused thickening of the epidermis in both treated yolk sac larvae and fry. Thyroid follicles were absent in the yolk sac larvae but present in the fry.

Practical diets supplemented with krill meal (5%), earthworm meal (5%), glycine (2%), sucrose (5%) or mussel extract as an attractant were fed for eight weeks to juvenile Penaeus monodon. The major protein sources of the diets were locally available full-fat soybean meal, fish meal and shrimp meal, and the crude protein level of each diet was adjusted to approximately 40%. For a four to eight-week period, dietary groups supplemented with any type of attractant resulted in better average weight gain than the control group (without any attractant). Prawns fed with a supplementary diet of earthworm meal registered the best growth rate (160% weight gain in eight weeks) which was significantly better than that of the control group. Dietary groups supplemented with earthworm meal and sucrose showed the best and worst survival rates, respectively, in zero to eight-week period. The feed conversion of the latter group was poorest among the dietary groups supplemented with the attractant.

Motoh (1980) reported 9 and 13 kinds of shrimping gear for the fry and the adult respectively, of which most of them are indigenously used today in the Philippines. Howerver, druing the continued ecological survey of penaeids in the country conducted by him and his staff, six kinds of shrimping gear or devices were additionally found by them, which have been used traditionally in the country. The reasons that the present author intends to introduce the gear or devices are as follwos: 1) To record theses unque devices from the nature conservation point of view, which were invented by local people through their long experiences, though devices been forgotten due to their poor catching effectiveness, and 2) To recommend the continuous use of these devices by local people, which impose much less construction technique and energy on the users compared to modern mechanized catching tools.