Growth of three strains of Oreochromis niloticus L. fry exposed to salinity stress in the presence of an internal reference fish were compared. The Central Luzon State University (CLSU) strain was obtained from the Freshwater Aquaculture Center, CLSU, Philippines. The ISRAEL strain was acquired from the Philippine government's Bureau of Fisheries and Aquatic Resources National Freshwater Fisheries Technology Center (BFAR-NFFTC), Munoz, Nueva Ecija. The National Inland Fisheries Institute (NIFI) strain was obtained from the NIFI, Bangkok, Thailand. Eight to nine full-sib families (replicates) per strain were split into two groups. One group was grown in freshwater for 2 weeks, acclimated to 32 ppt and reared for 2 weeks and finally grown in freshwater for another 2 weeks. Another group was contemporaneously grown in freshwater polyethylene tanks for 6 weeks. Each replicate family included a size-matched internal reference population of red tilapia strain. Two-way analysis of variance (anova) revealed no significant strain differences (P=0.081; r²=0.106). However, analysis of covariance with the internal reference strain used as a covariate showed significant (P=0.049; r²=0.638) strain effects on specific growth (based on standard length measurements). The ISRAEL strain showed consistently better growth rate in both saline and freshwater environments than the NIFI and CLSU strains. We estimated the statistical power of the two-way anova (ϕ=√(k′−1)(factor MS−s²)/(k′s>²); Zar 1984) to be ∼0.30. There was a 70% probability of a Type II error and no true difference in the growth of the three strains was detected. The use of internal reference strain as a covariate improved the r² from 0.106 to 0.638 and increased the efficiency of the test in detecting a true difference. Other strain comparison studies in our laboratory at the Southeast Asian Fisheries Development Center Aquaculture Department showed that the ISRAEL strain shows better growth than the NIFI and CLSU strains in a crowding stress tolerance experiment, when fed only with rice bran and under restrictive feeding regimes.

The study was conducted to determine if stunting of young bighead carp Aristichtys nobilis (Richardson) would affect subsequent growth and reproduction. Juveniles (3 g each) were stocked directly in cages (control) in a lake or stunted in tanks for 6, 12, 18 or 24 months before being stocked in cages. Initially, body weights and lengths of stunted carp in cages were significantly lower (P<0.05) than those of the control fish. The carp stunted for 6, 12 and 18 months showed growth compensation, although their weights and lengths were slightly lower than those of the control fish. The body weight and length of fish stunted for 24 months were the lowest throughout the rearing period. Sexual maturation occurred only in the control fish and those stunted for 6 and 12 months. However, the onset of gonad maturity was delayed significantly (P<0.05) in males stunted for 12 months and in both groups of stunted female fish. The relative fecundity (44 000–56 000 eggs per kg body weight) and number of 3-day-old larvae produced per female (78 000–89 000) did not differ significantly among the three treatments (P>0.05), but production was somewhat lower in fish stunted for 12 months.

This paper presents the results of an economic analysis of the aquaculture of two species of grouper E. coloides (orange‐spotted grouper, green grouper, red‐spotted grouper) and E. malabaricus (malabar grouper, black‐spotted grouper) for small producers in the Philippines. The findings of the analysis indicate that, based on the assumptions, grouper culture is financially feasible. However, the capital requirements for the broodstock, hatchery/nursery, and integrated system may be beyond the financial means of many small producers. These stages of grouper culture may need to be developed as a larger project by private investors or government. The capital investment requirement for grow‐out (not including purchase of transport boxes) is within the financial means of small producers. Loans or other incentives will need to be made available for the small producer, but the cash flow indicates that these loans can be repaid in the first year of production.

Fatty acid composition was determined in five candidate aquaculture species, mangrove red snapper (Lutjanus argentimaculatus), two rabbitfish (Siganus guttatus and S. canaliculatus), coral trout (Plectropomus leopardus) and striped jack (Caranx fulvoguttatus) sampled in the Central Philippines. Special attention was paid to arachidonic acid (ARA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Total lipids of hatchery-produced eggs and newly hatched larvae of mangrove red snapper unexpectedly had equal levels of ARA and EPA. Ovarian polar lipids were subsequently found to have intermediate or high ARA (5.5–10.7%) and DHA (14.4–20.4%) levels but relatively low EPA levels (1.5–1.9%), consequently showing high ARA/EPA (4.4–6.0) and DHA/EPA (7.4–14.9) ratios in wild mangrove red snapper and rabbitfish (S. guttatus and S. canaliculatus). Similar trends were observed even in hatchery-reared mangrove red snapper, rabbitfish (S. guttatus) and coral trout. Not only ovary but also liver and muscle contained relatively higher ARA compared with EPA in mangrove red snapper, regardless of the sample source. ARA, EPA and DHA levels in the polar lipids of wild fry (whole body) ranged respectively from 3.2% to 4.0%, from 2.7% to 4.7% and from 23.5% to 27.6% with intermediate or high ARA/EPA (0.8–1.5) and DHA/EPA (5.9–8.8) ratios in mangrove red snapper, rabbitfish (S. canaliculatus) and striped jack. As overall traits, the five species in the Central Philippines appear to have intermediate or high ARA and DHA levels with low EPA level, consequently having high ARA/EPA and DHA/EPA ratios compared to species in high and temperate northern hemisphere. Thus, the present results indicate that ARA is not a minor component in the tropical species, suggesting that ARA may be nutritionally much more important for egg development and larvae growth in the tropical species than in cold water species. The information of the present study can be used as a guideline for development of appropriate broodstock and/or larval diets in the Philippines.

This paper reviews various aspects of the biology and effects of 2 caligid copepods, Lepeophtheirus salmonis and Caligus orientalis, on wild and farmed fish in sea and brackish waters of Japan and adjacent regions. Lepeophtheirus salmonis is a common parasite of wild adult chum (Oncorhynchus keta) and pink (O. gorbuscha) salmon migrating in northern Japanese waters. Masu salmon (O. masou) have the lowest level of infection. Juvenile chum salmon are sometimes infected. This parasite is also found on salmonids in Korean and Russian waters. The species occurs on coho salmon (O. kisutch) and rainbow trout (O. mykiss) farmed in coastal waters of northern Japan, but its infection is not a serious problem, because only young fish are reared and harvested in less than a year of culture and thus no fish are cultured during summer. This situation is very different from that in Scotland, Ireland, Norway, and Canada where L. salmonis causes serious damage to farms of Atlantic salmon (Salmo salar). Caligus orientalis is a parasite of coastal marine and brackish-water fish in Japan and neighboring countries (Taiwan, China, Korea, and Russia). This parasite has a wide host range and has been reported from over 20 fish species from different orders and families. It infects farmed and experimentally reared fish, such as rainbow trout in Japan, grey mullet (Mugil cephalus) and black porgy (Acanthopagrus schlegeli) in Taiwan, and Mozambique tilapia (Oreochromis mossambicus) in China. Heavy infection results in appetite reduction and death of fish. The parasite is one of the most important pathogens at brackish-water fish farms in Far East Asia.

Species of the economically important gracilarioid seaweeds from the Philippines were studied to determine the monthly variation in agar quality. Yield, gel strength, melting and gelling temperatures, and sulfate contents were compared. Lowest agar yield was observed in Gracilaria changii in July (4.15%) and highest in Gracilariopsis heteroclada in March (20.84%). Gel strength was lowest in G. heteroclada in November (44 g cm^-2) and highest in Gracilaria tenuistipitata in January (874 g cm^-2). Melting temperature was lowest in G. heteroclada in November (68.7°C) and highest also in G. heteroclada in January (90.3°C). Gelling temperature was lowest at 34.4°C in G. changii and Gracilaria firma in November and December, respectively; and highest in G. heteroclada in October (45°C). Sulfate content was lowest in G. firma in November (0.16%) and highest in G. heteroclada in February (2.71%). The variation in the agar parameters could be due to different composition of agars of different species. Sulfate is significantly lower in Gracilaria firma. Yield is significantly higher in Gracilariopsis heteroclada. There is no significant difference in the gel strength, melting and gelling temperatures among species.

Apparent digestibility coefficients (ADCs) for dry matter (ADC_dm) and crude protein (ADC_cp) of selected feed ingredients were determined in vivo for grouper using passive faeces collection (Guelph System). A reference diet (RF) and test diets (consisted of 70% RF and 30% test ingredient) with 1% Cr₂O₃ as an inert indicator were used. An RF contained 45% protein, 10% fat and 15.7 kJ g⁻¹ metabolizable energy. Three isonitrogenous and isocaloric diets, each contained a test ingredient (white fish meal, white cowpea meal and ipil-ipil leaf meal), were used in a growth study based on ADC_cp of feed ingredients. An RF without Cr₂O₃ was a control. The ADC values of experimental diets were also determined. In grouper, the ADC_dm of white cowpea meal, defatted soybean meal, wheat flour and shrimp meal (74–76%) were significantly lower than that of squid meal (99%), but comparable with those of the fish meals (84–89%). No significant difference was observed between the ADC_dm of ipil-ipil leaf meal, rice bran and wheat flour (56–73%). The ADC_cp of white cowpea meal and defatted soybean meal were similar to those of the fish meals, squid meal and shrimp meal (94–99%). The ADC_cp of wheat flour was comparable with that of ipil-ipil leaf meal (79–83%). Rice bran had the lowest ADC_cp value of 43%. Based on specific growth rate (SGR), the growth of fish fed white cowpea meal-based diets was similar to that of the control fish (3.2–3.3% day⁻¹). Also, no significant difference was observed between the ADC_dm (68–72%) and ADC_cp (88–91%) of white cowpea meal-based diet and the control diet. The results suggest that ADC values can be used as indicators to determine the nutritional value of feed ingredients. White cowpea meal can be incorporated as a protein source in practical diet for grouper at 20.5% of the diet with no adverse effect on growth.

Viral nervous necrosis (VNN), also known as viral encephalopathy and retinopathy (VER), is an emerging disease affecting larvae and juveniles of many farmed marine fish species in Asia, Australia, Europe and North America. Mass mortality occurred in 14-day old larval sea bass Lates calcarifer at a hatchery in the Philippines associated with clinical signs such as abnormal swimming behavior and pale-gray discoloration of the body. Histological investigations in moribund fish revealed marked vacuolation in the retina and brain. Cytopathic effects (CPE) were observed in SSN-1 cells inoculated with the tissue filtrate of affected sea bass. A piscine nodavirus, the causative agent of VNN, was detected in the affected tissues and SSN-1 cells inoculated with the tissue filtrate of affected fish by RT-PCR. Electron microscopy revealed non-enveloped viral particles, 22-28 nm in diameter, in the cytoplasm of the brain and retina of affected fish and in the cytoplasm of VNN-infected SSN-1 cells after CPE appeared. These results indicate that mass mortality of sea bass larvae in the Philippines was caused by a piscine nodavirus.

Outbreaks of heavy infestation by the parasitic dinoflagellate Amyloodinium ocellatum in hatchery-reared milkfish (Chanos chanos) and mangrove red snapper (Lutjanus argentimaculatus) caused 100% mortality events in hatcheries in the Philippines. Parasites were recorded on the body surface in 14-day-old milkfish fry and on both skin and gills in 2-month-old snapper. Trophonts of A. ocellatum caused local erosions of fish skin and degeneration of epithelial cells at the sites of the parasite's attachment to the body surface. Separation and hyperplasia of gill epithelium and fusion of secondary lamellae at the distal parts of the gill filaments were common. High pathogenicity of A. ocellatum to fish may be attributed to the severe alterations of the fish gills, the disruption of the host's skin, and feeding of trophonts on hosts' epithelial cells. In-vivo treatments of A. ocellatum-infested snapper with a 1 h freshwater bath and 200 ppm H₂O₂ showed promising results. This is the first report of A. ocellatum infestation in milkfish and mangrove red snapper in the Philippines.