Milt volume, sperm density, and number of spermatozoa were determined to quantify milt production of mature sea bass after a single injection of LHRHa [(D-Ala6,Pro9-N-ethylamiide)LHRH] in saline solution and 17α-methyltestosterone in corn oil (MT). Two measures of sperm density, sperm count and spermatocrit, were highly correlated (r=0.85). Compared with control, milt volume and the number of spermatozoa collected increased but sperm count decreased (24% at 24 h) after a LHRHa (20 µg/kg body weight treatment, suggesting a stimulation of spermatozoa production and not merely milt dilution. Further milt dilution (44%) was induced by 80 µg/kg LHRHa (LHRHa80) at 12 h post-treatment but not by 200 µg/kg MT (MT200) alone. A milt dilution of only 27% at 12 h after simultaneous injections of LHRHa80 and MT200 may indicate some inhibitory effect of MT on the efficiency of LHRHa. These results demonstrate that the stimulation of milt production by LHRHa involves testicular hydration resulting in milt dilution.

Ovaries of Oreochromis mossambicus exposed to sublethal concentrations of nickel sulphate (0.5 mg/1 and 1.0 mg/1) were histologically analyzed. Changes following exposure to 0.5 mg/1 nickel sulphate include irregularities in the shape of egg follicles, subcellular oocyte damage, lifting off of the theca layer and proliferation of connective tissues. In the ovaries exposed to 1.0 mg/1 nickel sulphate, degenerative changes are worse. Invasion by connective tissues is extensive, oocytes have bizarre shapes, yolk granules are scattered in the interfollicular spaces, abnormal growths are evident and previttelogenic oocytes abound. Nickel is a toxicant in Oreochromis mossambicus ovaries.

Clarias macrocephalus is endemic yet dwindling freshwater foodfish in the Philippines. Induced breeding protocol was developed by monitoring the size and maturation of eggs at 0-48 h after a simultaneous injection of luteinizing hormone-releasing hormone analogue (LHRHa; 0.0005 - 0.10 µg/g BW) and pimozide (PIM; 1 µg/g BW). Based on its similar osmotic pressure with catfish plasma, eggs were fixed in 1% phosphate-buffered formalin. Mean egg diameter of fish that were induced to mature increased during ovulation. Oocyte maturation, indicated by oocytes with germinal vesicle breakdown (GVBD), was observed at least 12 h post-injection in fish given 0.01 - 0.10 µg LHRHa + 1 µg PIM/g BW, followed by ovulation 4 h thereafter. Results showed that a simultaneous injection of C. macrocephalus with 0.05 µg LHRHa + 1 µg PIM/g BW at 1800-1900 h followed by stripping at 16-20 h post-injection resulted in high ovulation, fertilization and hatching rates.

This paper describes various types of shrimping and prawning gear and devices, most of which have been traditionally used in the Philippines, with some ecological notes. This study provides basic information on prawn culture and fry collection, which will be useful for private fishpond operators and workers.

Feed is the single most important input in increasing aquaculture production and profits. Success or failure in augmenting yield with feeding depends, to a large extent, on the quality of the diet. Feed quality, generally perceived as the responsibility of the feed manufacturer, is affected by factors outside of the plant such as handling, storage, and use. Thus, the maintenance of feed quality becomes partly the responsibility of the farmer. Every fish farmer must be familiar with the nature and occurrence of major feed quality problems and able to prevent and control them. This paper is based on a farmer's viewpoint. Valuable insights are provided for the feed manufacturer.

Three groups of pond-reared Penaeus monodon broodstock were fed formulated diet in combination with carotenoid-containing natural food: mussel + shrimp broodstock pellet (MBP), crab + BP (CBP), and Artemia + BP (ABP). After four months, maturation and spawning rates did not differ significantly among treatments. After eyestalk ablation, MBP-fed shrimps Initially spawned 20 days; 34 days for CBP-fed; 50 days for ABP-fed shrimps. The number of eggs per g body weight of spawner (1616-2359 eggs /g BW) did not differ significantly among all groups. Only nauplii from MBP-fed broodstock reached postlarval stage. Rematuration was observed only in MBP- and CBP fed shrimps. Sperm count was highest in MBP- and lowest in ABP-fed shrimps at the final phase of the test.

An in vitro method of determining protein digestibility was modified for application in white shrimps. The protein digestibility of 21 locally available feedstuffs were determined. Vitamin-free casein was used as reference protein. To verify in vitro results, a feeding experiment was conducted using 300 shrimps with average initial weight of 0.075 g. The shrimps were fed isonitrogenous and isocaloric diets containing test ingredients with high (27.6% -33.7%) and low (4.0%-10.5%) digestibility for 61 days. Seawater temperature ranged from 26 to 29°C and salinity from 30 to 33 ppt. Defatted soybean meal (27.2% digestibility) was used as control. Growth and survival were determined. Animal proteins (40.9%-90.9%) were more digestible than plant proteins (0.0%-33.7%), although digestibility of papaya leaf meal (33.7%) was comparable with those of shrimp head meal (40.9%) and Peruvian fish meal (40.7%). Green mungbean meal was most digestible (27.6%) among the legumes. Protein digestibility of defatted soybean meal (27.2%) was significantly higher than that of unprocessed soybean meal (9.4%). Black cowpea meal and ricebean meal were not digestible. Results also showed that white shrimps given a diet containing cassava leaves performed best with weight gain, specific growth rate, and survival (706.4%, 3.44 and 49%) comparable with white cowpea meal (701.3%, 3.35 and 40%) and defatted soybean meal (726.8%,3.50 and 33%), followed by papaya leaf meal (505%, 3.02 and 38%). Shrimps fed a diet containing green mungbean meal showed the poorest response (344.2%, 2.46 and 18%). These results indicate that in vitro protein digestibility is not correlated with growth and survival. The amino acid pattern, anti-nutritional factors, and palatibility of the diets are other important factors that may influence the growth of P. indicus.

Two locally grown seaweeds, Kappaphycus alvarezii and Gracilaria heteroclada, were tested as binders in diets for shrimp juveniles to minimize the use of wheat flour, a common binder. The seaweeds were washed, dried, ground, and made into paste. Seaweed meals were added to an isonitrogenous diet containing 5% flour at 5, 10 and 15%. The control diet contained 15% flour (no seaweed meal). The diets were fed to juvenile Penaeus monodon for 56 days to assess the acceptability of the seaweed meals in terms of shrimp growth, survival and feed conversion ratio (FCR). Seven dietary treatments, each with three replicates, were arranged in a completely randomized design. Treatment means were compared by analysis of variance and Duncan's multiple range test.Growth of shrimp fed diets with 5% and 10% G. heteroclada, and 10% K. alvarezii did not differ significantly but was higher than the rest of the treatments. Only those fed 10% G. heteroclada had growth similar to those fed the control diet. Diets with 5% and 10% K. alvareziii and 10% G. heteroclada had the best FCR. Shrimp survival decreased as the level of G. heteroclada increased. Survival was not affected by the level of K. alvarezii in the diet.Water stability of the diets was assessed in 4 h. High water stability was observed in the diet with 10% G. heteroclada (91%), 5% G. heteroclada (90%) and the control (90%). The rest of the diets were 87-89% stable. Thus, 10% G. heteroclada or 10% K. alvarezii could be used to supplement 5% flour as binders in shrimp diets with no adverse effect on growth and survival.

An eight-week feeding experiment with juvenile sea bass (about 15 g) was conducted in 500-1 fiberglass tanks to screen the most cost-effective practical diet for use in ponds and floating cages. Eleven formulations and one control feed were tested. Protein sources used were locally available ingredients such as fish meal, shrimp head meal, scrap squid meal, cow's blood meal, poultry feather meal, leaf meals, soybean meal, and mung bean meal. The diets contained a combination of animal and vegetable protein sources such that the essential amino acid composition was close to the requirement or tissue levels. Crude protein and fat levels were about 42% and 8.3%, respectively. Fish were fed ad libitum twice a day at 0800 and 1600 h. Best weight gain (189%) and feed conversion ratio (FCR, 1.7) were observed in fish given a combination of fish meal, shrimp head meal, scrap squid meal, soybean bean meal, and kangkong leaf meal as protein sources. This was followed by those given a combination of fish meal, shrimp head meal, scrap squid meal, soybean meal, and ipil-ipil leaf meal (139% weight gain, FCR of 2.2). Worst growth (22%) and FCR were observed in fish given a combination of fish meal, cow's blood meal, scrap squid meal, soybean meal, and mulberry leaf meal. Control fish given a combination of fish meal, shrimp meal, and soybean meal showed weight gain of 195% and FCR of 1.8. Survival was high (83-100%) in all treatments. The two diets which gave the best growth rates, survival, and FCR in the screening phase can be tried in ponds and floating net cages.

The most economical combination of dietary protein and feeding levels for milkfish culture in brackishwater ponds was determined. Milkfish juveniles (average weight, 5 g) were stocked at 7000/ha and fed two diets containing 24% or 31% dietary protein at 2% or 4% of body weight.There was no interaction between feeding level and dietary protein on growth, feed efficiency, and energy assimilation of milkfish. This indicates that the response of milkfish to change in protein levels is not influenced by ration size. Regardless of protein levels, the final weight, weight gain, specific growth rate, and production of milkfish were significantly higher (P < 0.05) when fed at 4% body weight than at 2%. As culture progresses, differences in weights of fish fed varying protein levels were still insignificant. This could be attributed to the balanced amino acid profile of both diets. But, fish weights vary significantly among milkfish fed at different levels. The higher growth at 4% feeding level could be due to the higher amount of amino acids supplied to the fish for protein synthesis. These results suggest that growth will depend on the amount of amino acids supplied when the amino acid profile of the diet is balanced. Higher energy assimilated by milkfish at higher feeding rate demonstrated that energy supply also influences growth. Partial budgeting analysis revealed that bigger profits can be earned by using an amino acid balanced diet with 24% protein at a feeding rate of 4% of body weight. The greater amount of feed given at higher feeding rate can be compensated by faster growth and higher production.