The performance of an artificial practical diet, kappa-carrageenan microbound diet (C-MBD) was assessed on Penaeus monodon larvae at the SEAFDEC Broodstock and Maturation Experimental Laboratory in March 1986. Shrimps were reared from zoea to post-larvae using five dietary treatments: (a) natural food - Chaetoceros calicitrans and Artemia salina ; (b) C-MBD; (c) combination of natural food and C-MBD; (d) commercial diet (microencapsulated, MED); (e) combination of natural food and commercial diet. Results showed slow development with larvae fed the commercial diet. Feeding with C-MBD in combination with natural food resulted in the highest % survival among treatments (69.6), but this was not significantly different (p > 0.05) from those obtained with larvae fed natural food alone, C-MBD alone or their combination.

Oreochromis niloticus fingerlings were stocked at three different initial size ranges of 1-3, 7-12 and 20-30 g in fixed net cages in Laguna Lake, Philippines. These were reared without supplemental feed for 120 days. Fingerlings with the biggest initial size at stocking were the most efficient in terms of average weight gain, average final fish weight and total fish production.

The effect of loading density, transport duration, water temperature, and salinity on survival of young rabbitfish (Siganus guttatus Bloch) under simulated transport conditions was investigated. The rocking motion of transport was simulated by an electric shaker. At ambient temperature and salinity (28°C/32‰S) increasing loadin density and transport duration resulted in decreasin fish survival rates. When both temperature ant salinity (20°C/20‰S) were lowered survival improved sinificantly. Dissolved oxygen, water temperature, and salinity were critical factors affecting survivaf of young rabbitfish during simulated transport. Based on the results, a density of 100 fish/L can be packed for 8 hours of transport and 300 fish/L for 2 hours at 28°C and 32‰, and about 200 fish/L for 4 hours at 20°C and 20‰S.

Mudcrabs, Scylla serrata Forsskal, were monocultured at different stocking densities: 5000, 10 000, 15 000 and 20 000/ha for 90 days. Highest mean weight, survival and relative growth increment (P>0.05) were obtained from a stocking density of 5000/ha. Best feed conversion ratio of 1.72 and corresponding gross production of 1019 kg/ha per crop were attained at the same stocking density. The economic indicators, i.e., return on investment and return on equity, were also highest at 5000/ha stocking density and the payback period was shortest. Partial budgeting showed that no incremental benefit accrued from stocking beyond 5000/ha. Sensitivity analysis showed that even if the value of mudcrab were to decrease by 28%, mudcrab monoculture would still be economically viable.

P. monodon juveniles with an initial mean weight of 0.62 g were fed isonitrogenous (45%) and isolipidic (10%) semi-purified diets containing 10, 20 and 30% trehalose, sucrose and glucose for 56 days. Shrimp fed the diet with 20% trehalose had the highest weight gain. Of the three types of sugar tested, shrimp fed diets containing trehalose and sucrose exhibited better weight gains than those fed glucose diets. A dietary sugar level of 20% resulted in the best weight gain whereas the 30% level gave the lowest weight gain. The survival of shrimp was also affected by the type of carbohydrate fed. Trehalose and sucrose diets promoted higher survival rates than glucose diets. The different types and levels of carbohydrates showed combined effects on the dry matter percentages of crude protein and total lipid. Trehalose and sucrose diets generally promoted increased protein deposition. Trehalose at 30% and sucrose at 20% depressed lipid content.

Penaeus monodon postlarvae were fed with formulated diets containing either soaked or unsoaked Leucaena leaves. A similarly prepared feed with soybean in place of Leucaena was used for comparison. Results were analysed by statistical and histological methods. Results of the 4-week feeding experiment showed that mean weight gains and percentage survival of the prawns fed with the two Leucaena-containing diets were higher, but not significantly different from soybean-containing diet. The content of the poisonous amino acid mimosine in the Leucaena leaves could be reduced about 70% by soaking the leaves in freshwater for 24 h. Highest weight gain was obtained with the feed containing these soaked leaves. In addition to growth and survival, the R-cells of the midgut glands of the postlarvae were investigated by light and electron microscopy. Although the statistical growth values and the proximate analyses of the test diets were similar, a food-specific ultrastructure was established after only 4 days of feeding. All diets resulted in subcellular characteristics typical for well fed prawns and, at that time, the Leucaena diets were already slightly superior to the soybean control. This indicates that different sources of macronutrients lead to different ultrastructures even if the proximate analyses of protein, carbohydrate and lipid are similar. Only slight changes in the R-cells were observed after 11, 20 and 28 days in the prawns fed with the soybean diet compared to 4 days of feeding. In the diet containing unsoaked Leucaena leaves, however, many R-cells became heavily damaged after 20 and 28 days, whereas the prawns fed with the diet containing soaked leaves exhibited less pronounced distortion. Statistical analyses of growth and survival rate did not show these adverse effects at that time. Although it is highly probable that the mimosine is responsible for those pathological symptoms, complementary experiments could not clearly prove that. The effects of feed components are visible on the cellular or organ level after only a few days, whereas the individuals (organism level) reflect them about 10 days later. Another 10 days later the changes are manifested in the population. Therefore it is suggested to use histology in nutrition studies as a supplementary source of information to statistical and biochemical parameters. The midgut glands can further be used to monitor the nutritional condition of prawns in aquaculture, sea ranching, and in ecological investigations. The study confirms that Leucaena leaves are a promising protein source for prawn diets if mimosine could be reduced to a very low level. A mimosine level of 0.25% in the feed is still too high, if the diet is used uninterruptedly for several weeks.

Larvae of the oyster Crassostrea iredalei were reared in the laboratory from eggs through settlement. The oysters were induced to spawn by increasing the temperature by 5-10°C and sometimes by adding stripped oyster sperm to the spawning dishes. Eggs avareaged 48 µm in diameter. The straight-hinge veligers appeared 22 to 26 h after fertilization. The larval shell length increased from 64 to 84 µm in the straight-hinge stage, from 85 to 275 µm in the umbo stage, and from 210 to 275 µm in the pediveliger stage. Eye-spotted pediveligers were observed mostly at lengths greater than 225 µm. The hinge line did not increase much with larval growth. Although length was initially greater than height, the increase in height was much faster due to the development of the umbo. Height was greater than length in more advanced larvae. Valve growth was asymmetrical and unequal, with the left valve generally larger. Settlement and metamorphosis occurred 20 days from fertilization at lengths of 270 µm and greater, when the oyster larvae were reared at 26.5 to 30°C and salinities of 30 to 32 ppt. The larval hinge structure consisted of minute dentition on the central portion of the provinculum and large rectangular teeth on both ends. These teeth became obscured in advanced larvae due to the skewed development of the umbo. Data derived from the laboratory culture of larvae of Crassostrea iredalei may be used in spatfall forecasts for the collection of larvae from the wild and as baseline information for the hatchery culture of oyster larvae.

Development of fin-supports and fin-rays was observed in larval and juvenileChanos chanos, Chondrification of the caudal complex started at 4.70 mm SL. Ossification of the caudal elements started at 7.80 mm SL and was nearly completed at about 30 mm SL. Cartilaginous fusion of caudal elements, which occurs in hypurals of higher teleostean fishes but is not seen in lower teleosts, was observed between the neural arch of the preural centrum 1 and that of the ural centrum 1 via a small cartilage bridging the distal tips of the two arches. Caudal finrays began to develop at 6.60 mm SL, and an adult complement of principal rays was attained at 7.35 mm SL. Dorsal and anal pterygiophore elements were first evident at 6.70 mm and 6.65 mm SL, respectively. All proximal radiais were formed at 8.15 mm SL in both fins. Formation of dorsal and anal fin-rays started simultaneously at 8.60 mm SL, and adult fin-ray complements were attained at 10,00 mm and 10.70 mm SL, respectively. In the pectoral fin, the cleithrum, coraco-scapular cartilage and blade-like cartilage (fin plate) had already been formed at 4.65 mm SL. The mesocoracoid was observed to originate from the coraco-scapular cartilage and become detached from it in the course of ossification. Pectoral fin-ray formation started at 13.80 mm SL and was completed in number of rays at 20.00 mm SL. In the pelvic fin, the basipterygium was first evident at 13.00 mm SL. Pelvic fin-rays appeared at 13.80 mm SL and attained their adult count at 17.15 mm SL.

Increasing fish production through polyculture was clearly demonstrated to the fishfarmers in Laguna lake. The rearing of different species of fish of proper number and species combinations had resulted to the efficient utilization of all the available food niches/zones in the lake. Fish production is site specific in Laguna lake. Wide variation in growth increment and fish yield were observed among the different bays and among farm sited within a bay. The final mean weights of the fish species were 355 mg to 2300 g for bighead carp, 32 g to 103.3 g for tilapia and 8.3 g to 1800 g for common carp.

The in vivo effect of mycostatic levels of fungicides against the fungi Lagenidium sp. and Haliphthoros philippinensis was tested on Penaeus monodon eggs and larvae. Hatching rate and survival of nauplii, zoeae, myses and postlarvae exposed to 10 mg/l benzalkonium chloride, 1 mg/l Clotrimazole, 1 mg/l crystal violet, 10 mg/l 2,4-D, 10 mg/l Daconil, 20 mg/l laundry detergent, 1 mg/l Econazole nitrate, 10 mg/l Resiguard, 0.2 mg/l and 10 mg/l Treflan-R, and 0.01 mg/l and 0.2 mg/l trifluralin were monitored daily for 96 h in a static bioassay in glass aquaria. Test chemicals did not have an inhibitory effect on hatching rate but survival rate of hatched nauplii was significantly reduced in most treatments except those with 0.2 mg/l Treflan-R and 0.2 mg/l trifluralin. Tests with zoeae, myses and postlarvae indicated that 0.2 mg/l Treflan-R as well as 0.01 mg/l and 0.2 mg/l trifluralin did not adversely affect survival. In addition, application of 10 mg/l benzalkonium chloride caused no significant mortalities among exposed myses.