Identification and examination of the physiological characteristics of Pseudomonas sp. isolated from fry of Sarotherodon niloticus (L.) was conducted. Based on morphological and biochemical tests, the bacterium was identified to be a strain closest to Pseudomonas fluorescens. In vitro physiological growth patterns at varying temperatures, NaCl concentrations, and pH were observed for a maximum of eleven days incubation while growth of the test bacterium into various water media were observed for a maximum of 148 days. Bacterial growth occurred between 10° to 41°C with optimum growth at 25° to 30°C. The bacterium tolerated NaCl concentrations of 0 to 50 ppt. Optimum growth, however, was obtained from 0 to 15 ppt. It was found that growth was possible only at pH 5.0 to 9.7. Optimum growth occurred at pH ranging from 5.7 to 8.4. Inoculation of the test bacterium into different freshwater media obtained from various sources resulted in growth and rapid multiplication. Viability was maintained throughout the 148 day incubation period. Growth in the brackishwater medium was observed only until 50 days. No growth was observed in the seawater medium.

1. Groups of rainbow trout (Salmo gairdneri) (mean weight 14 g) were given diets containing 0.8, 1.3, 2, 3, 4 or 6 g tryptophan/kg diet for 12 weeks. 2. By analysis of the growth results, the dietary requirement of tryptophan was found to be 2.5 g/kg diet (equivalent to 50 mg/kg biomass per d). 3. Carbon dioxide expired by trout following intraperitoneal injection of [¹⁴COOH]tryptophan contained little radioactivity when dietary tryptophan level was low but, above 2.0 g/kg diet, it increased rapidly with increasing dietary tryptophan level. The break point in the dose-response curve did not, however, coincide with that from the growth results. 4. Changes in concentrations of free tryptophan in blood and liver and activity of hepatic tryptophan pyrrolase (EC 1.13.11.11) in response to changes in dietary tryptophan concentration did not provide reliable indicators for quantifying dietary requirement. Unlike the situation in mammals, blood tryptophan was not protein-bound to any appreciable extent. Tryptophan pyrrolase of trout has properties which suggest it has no apoenzyme form. 5. In fish given adequate levels of tryptophan injected intraperitoneally with a tracer dose of [¹⁴COOH]tryptophan, 60% of the dose was incorporated into body protein within 1 d. The turnover of the label in this protein is very slow. 6. Those trout given diets deficient in tryptophan suffered from severe scoliosis and lordosis as well as having increased liver and kidney levels of calcium, magnesium, sodium and potassium.

The hepatocytes of milkfish (C. chanos) fry and fingerlings offered a variety of diets differ considerably as was shown by means of transmission electron microscopy. For fry it was shown that a 7 day starvation period results in a heavily altered hepatocyte ultrastructure but that even in this stadium fast regeneration was possible. Chlorella turned out to be the worst diet, among the artificial diets, the trout diet provoked the best regeneration. In fingerlings a prolonged starvation period was necessary to affect hepatocytes. In some cases considerable indications of liver cell degeneration were found after feeding certain diets for 2-3 months. Even dried lumut and lab-lab did not create optimal hepatocyte ultrastructure. Feeding with cod liver oil did not result in deposition of lipid droplets in the hepatocytes of fingerlings, what is in contrast to milkfish fry hepatocytes.

The effect of the rotifer, Brachionus plicatilis, grown on unialgal cultures of Isochrysis galbana, Tetraselmis sp. and Chlorella sp. on the hepatocytes of milkfish fry was evaluated by electron microscopy. Rotifers grown on the three different species of phytoplankton brought about different ultrastructural features in milkfish fry hepatocytes. Best results were obtained from fry reared on Isochrysis-fed rotifers. The use of marine Chlorella-fed rotifers as feed for fry resulted in the poorest hepatocyte ultrastructure, indicating that this was nutritionally the least adequate cultured food. None of the three diets, however, produced an optimal hepatocyte ultrastructure similar to that obtained by feeding the fry with a mixture of artificial feed and newly hatched Artemia nauplii.

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%).