Mangrove red snapper fed advanced broodstock diets containing squid meal and squid oil exhibited higher hatching rates, cumulative survival and survival activity index than those fed a basal diet or a basal diet supplemented with mixture of antioxidants. On the other hand, fatty acid analyses of ovaries and fry of wild fish and eggs and larvae of broodstock fed raw fish revealed high arachidonic acid (ARA) and docosahexaenoic acid (DHA) levels and relatively lower eicosapentaenoic acid (EPA) levels consequently showing high ARA/EPA and DHA/EPA ratios compared to cold water species. This suggests that ARA may be nutritionally more important for egg and larval development and survival in tropical marine fish and its supplementation in broodstock diets may enhance reproductive performance of mangrove red snapper.

A reliable breeding technique was developed for the mangrove red snapper, Lutjanus argentimaculatus (Forsskal 1775), to help sustain the aquaculture of this immensely popular species in Southeast Asia. Using standardized indices of female maturity (based on mean oocyte diameter of ≥0.40 mm), time of injection (1000–1130) and sex ratio (one female to two males), a single injection of 100 μg kg⁻¹ luteinizing hormone-releasing hormone analogue (LHRHa) (n=16 fish), but not 50 μg kg⁻¹ (n=five fish), successfully induced egg (62.5% success rate) and larval (43.8%) production. Human chorionic gonadotropin (hCG) at 500 IU kg⁻¹ (n=five fish) also failed to induce spawning, but doses of 1000 (n=22 fish) and 1500 IU kg⁻¹ (n=15 fish) gave spawning (77.3% and 80.0% respectively) and hatching success rates (72.7% and 60.0% respectively) that were not significantly different from those of 100 μg kg⁻¹ LHRHa. No spawning was observed in saline-injected controls (n=seven fish). While mean spawning latency, egg diameter, egg production per spawn, percent egg viability, hatching rate, percent of normal larvae and cumulative survival of eggs to normal larvae did not differ significantly among the effective hormones and doses, 1000 IU kg⁻¹ hCG had a higher percentage (76.5%) of total spawns with egg production per spawn in excess of one million than those of 1500 IU kg⁻¹ hCG (50.0%) and 100 μg kg⁻¹ LHRHa (40.0%). Mangrove red snapper spontaneously spawned from March–April to November–December with a peak of egg collection and spawning in May–June. Egg collection per spawn ranged from 0.05 to 6.35 million. Spontaneous spawning of mangrove red snapper exhibited lunar periodicity with spawns mostly occurring 3 days before or after the last quarter and new moon phases and occurred consistently between 02:00 and 04:00 hours. High fecundity and good egg quality, coupled with the ability to respond to induce spawning or natural spawning in captivity, provide a sound basis for improving the sustainability of red snapper aquaculture in Southeast Asia.

Juveniles of the Asian catfish Clarias macrocephalus (3.6±0.17 g; 78.0±0.09 mm) were fed one of four diets: a laboratory-formulated diet of 18.9% (Diet 1) or 34.2% (Diet 2) protein, a com- mercial feed pellet of 28.9% protein (Diet 3) or a diet of 80% blanched chicken entrails and 20% rice bran (31.7% protein; Diet 4). After 120 days of culture, catfish fed Diet 2 grew significantly better (p<0.05) than the other groups, reaching 108.9 g and 232.8 mm (daily weight gain 0.88 g; specific growth rate 2.9%), with a condition factor of 0.86 and production of 18.2 kg per 25 m2 pen. Feed conversion with Diets 2 and 3 (2.5 and 2.3, respectively) was better than with Diets 1 and 4 (3.4 and 5.0). Survival (68-81%) did not differ significantly among treatments (p>0.05). Catfish fed Diet 2 had the highest apparent lipid retention (131.7%). The protein efficiency ratio was lowest (1.3) in Diet 2, but did not differ significantly from Diets 1 and 3. Catfish fed Diet 4 were fatty and had a lower crude protein content. Results suggest that C. macrocephalus fed 34.2% crude protein have a significantly higher weight and total yield. Further, a taste test showed that odor, flavor and appearance did not differ amongst the diets.

Excessive dietary phosphorous (P) concentrations in effluents from aquaculture present a major environmental problem. We therefore studied the effect of dietary P and vitamin D₃ on P utilization by rainbow trout-fed practical diets and on P concentrations in the soluble, particulate and settleable components of the effluent from fish tanks. Rainbow trout (average weight: 78 g, initial biomass: 13 kg in 0.7 m³ tanks) were fed for 11 weeks, practical diets that varied in total P, available P, and vitamin D₃ concentrations. Soluble, particulate (10–200 μm) and settleable (>200 μm) P in the effluent were sampled every 0.5–6 h for 1–3 days in the third and eleventh weeks of the experiment. Trout in all diets more than doubled their weight after 11 weeks. Increasing the concentrations of available dietary P from 0.24% to 0.88% modestly enhanced growth rate. Feed conversion ratio (FCR) and biomass gain per gram P consumed decreased as dietary P concentrations increased. Carcass P, daily P gain, and plasma P concentrations were lower in fish fed with low P diets. Soluble P concentrations in the effluent peaked immediately after and again 4–6 h after feeding, and is a linear function of available dietary P. No soluble P would be produced during consumption of diets containing less than 0.22±0.02% available P. Above this dietary concentration, soluble P would be excreted at 6.9±0.4 mg/day/kg for each 0.1% increase in available dietary P. Particulate P concentrations in the effluent were independent of dietary P concentrations. Settleable, presumably fecal, P concentrations tended to increase with dietary P concentrations. In trout fed with low P (0.24% available P, 0.6% total P) diets, 60% of total dietary P were retained by the fish and the remaining 40% were excreted in the effluent as settleable P (20–30%) and particulate or soluble P (10–20%). In trout fed with high P (0.59–0.88% available P; 0.9–1.2% total P) diets, 30–55% of total dietary P was retained by fish, and the remaining 15–25% appeared in the effluent as settleable P, 20–55% as soluble P, and 5–10% as particulate P. Vitamin D₃ did not affect fish growth nor effluent P levels. Physicochemical management of aquaculture effluents should consider the effect of diets on partitioning of effluent P, the peaks of soluble P concentration following feeding, and the contributions of particulate P to total P in the effluent. Increasing our understanding of how dietary P is utilized and is subsequently partitioned in the effluent can contribute significantly towards alleviating this important environmental and industry problem.

A 12-week feeding trial was conducted to evaluate the use of feed pea meal as a dietary protein source for juvenile milkfish. Six isonitrogenous (30% crude protein) and isocaloric (16.5 kJ/g) practical diets were formulated. The control diet contained fish meal, soybean meal, meat and bone meal and copra meal as principal protein sources. Feed pea meal was progressively substituted at 0%, 5%, 10%, 15%, 20%, 25% and 30% of total protein. A leading commercial milkfish feed was also tested as an additional control. The experimental diets were fed to triplicate groups of milkfish fingerlings (mean initial weight of 0.42±0.01 g) at 10% body weight/day. Growth performance (expressed as percentage of weight gain and SGR), survival, feed conversion ratio (FCR) and protein efficiency ratio (PER) of milkfish fed diets with up to 10% substitution of the dietary protein with feed pea meal were not significantly different (P>0.05) compared to fish fed the control diet. Replacement with feed pea meal at 15% and higher levels led to milkfish fed these diets showing a significantly lower growth response compared to fish fed with the control without any feed pea meal. Nevertheless, it was observed that milkfish fed diets with up to 20% of total dietary protein substitution with feed pea meal showed better growth rates and feed conversion ratios than the commercial feed control. Whole body composition (crude protein, crude fat, crude fiber, nitrogen-free extracts and ash content) of milkfish fed the various test diets was not significantly different. Apparent digestibility coefficients of feed pea meal and experimental diets in milkfish were also determined. Results indicate that feed pea meal is an acceptable protein source and can replace up to 20% of the total dietary protein in milkfish diets.

The potential of feed pea meal as an alternative protein source to soybean meal in practical diets for the juvenile tiger shrimp, Penaeus monodon, was assessed in several experiments. Six isonitrogenous diets were formulated to contain 40% protein. Protein from the feed pea meal replaced 0%, 20%, 40%, 60%, 80%, and 100% of the protein from defatted soybean meal in the diets. These values were equivalent to 0%, 5%, 10%, 15%, 20%, 25%, respectively, of the total protein in the diet. A negative control with no protein sources was added to the treatments. Twelve shrimp post-larvae with an average weight of 0.02±0.01 g were randomly assigned in thirty-five 60-l oval tanks equipped with a flow-through seawater system. The shrimp were fed the formulated diets at a daily feeding rate of 20–25% body weight for 90 days in five replicate samples. No significant differences (P>0.05) were observed in weight gain, feed intake, feed conversion ratio (FCR) and protein efficiency ratio (PER) of shrimp fed diets 0 up to the highest level of replacement. Weight gain of shrimp fed the negative control was, however, significantly lower (P<0.05) compared to the rest of the treatments. Specific growth rates (SGR) of shrimp showed likewise no significant differences among treatments except for the negative control. Survival of shrimp for all treatments ranged between 75% and 100%. The apparent dry matter (ADMD) and protein (APD) digestibilities of the dry feed pea in P. monodon were high at 73.38±4.98 and 92.74±2.62, respectively. Digestibility coefficients for dry matter and protein for the feed pea meal-based diets increased with increasing level of feed pea replacement. There were no significant differences in whole body composition (dry matter, protein, lipid, ash, fiber) of shrimp fed the various diets with feed pea replacement. Pellet water stability was similar for all diets even up to the highest level of replacement. The results have demonstrated that feed pea meal has a very good potential as a substitute protein source up to 100% of the protein from defatted soybean meal, which is equivalent to 25% of the total protein in the diet. An inclusion level of up to 42% in the juvenile shrimp P. monodon practical diet did not manifest any adverse effects on growth, feed intake, FCR, survival, body composition, and digestibility coefficients for dry matter and protein of the shrimp.

A series of experiments were conducted to examine the effects of salinity, aeration and light intensity on oil globule absorption, feeding incidence, and growth and survival of early-stage Epinephelus coioides larvae. Newly hatched larvae were transferred to 40-L aquaria at a density of 1500 individuals/aquarium. Larvae were exposed to different levels of aeration (0 mL/min per L, 0.62 mL/min per L, 1.25 mL/min per L, 2.50 mL/min per L, or 3.75 mL/min per L); salinity (8 ppt, 16 ppt, 24 ppt, 32 ppt, or 40 ppt); and light intensity (0 lx, 120 lx, 230 lx, 500 lx, or 700 lx) for 4–6 days. Twenty larvae were sampled daily at 11:00 hours to measure for total length (TL), oil globule volume, and feeding incidence. Survival rates were determined by counting the total number of larvae remaining in each aquarium at the end of the experiment. Significantly higher survival rates (P < 0.05) were observed at aeration levels of 0.62 mL/min per L and 1.25 mL/min per L, at salinity levels of 16 ppt and 24 ppt, and at light intensities of 500 lx and 700 lx. The influence of aeration level, salinity and light intensity on oil globule absorption, feeding incidence, and growth and survival of early-stage grouper larvae are discussed.

The bacterial level of the water, sediment and cultured shrimp (Penaeus monodon) from different ponds were determined using a general medium, a presumptive Vibrio medium and a presumptive Pseudomonas–Aeromonas medium. Samples were taken from ponds that had not used any antimicrobial, ponds that had previously used and also ponds that were currently using oxolinic acid (OXA). The bacterial level in the sediment was higher than in the water using all three media. More bacteria existed in the pond system than in the receiving environment. Shrimp hepatopancreas harbored more bacteria than the lymphoid organ. The Vibrio density of the pond and bacterial levels in the shrimp were correlated with the use of the antimicrobial. The Vibrio level of the pond samples and microbial density of shrimps were higher from ponds that had not used any antimicrobials. The percentage recoveries of resistance to oxytetracycline (OTC) and OXA in bacteria from shrimp ponds and cultured shrimps were also determined using Zobell's marine agar, Pseudomonas–Aeromonas selective agar and thiosulfate citrate bile sucrose agar (TCBS) with the addition of either 25 μg/ml OTC or 25 μg/ml OXA. Presumptive Vibrio bacteria and other bacterial taxa recovered from the pond/receiving water/sediment from all three sites showed some degree of resistance to OTC and OXA. However, a higher percentage recovery of strains resistant to OTC than to OXA was observed among the presumptive vibrios and other bacterial taxa. Pseudomonas and Aeromonas bacteria were more resistant to OXA compared with the vibrios. All bacterial taxa resistant to OTC were more readily recovered from the water samples than from the sediment samples. In general, between the samples from the pond and from the receiving environment, a higher percentage of resistant strains was observed in the latter. Higher percentage recovery of bacteria resistant to OXA was observed in shrimp from ponds currently using OXA than those from ponds that had not used any or those that had previously used them. The results of the present study showed that the percentage recovery of resistance reflected the pattern of antimicrobial use.

Fish landings in Malalison Island, west central Philippines were monitored from June 1995 to January 1997 to determine species composition of catch, catch per unit effort (CPUE) and yield from the different fishing areas. A total of 596 fishing operations were recorded from the five fishing areas namely Nablag, Balabago and Salangan patch reefs and North and South fringing reefs. CPUE (kg fisher^-1 hr^-1) was 0.71 for hook and line, 1.16 for speargun, 2.80 for hookah (speargun with compressor), 1.29 for set gill net, 1.30 for drive-in gill net and 2.23 for drift gill net. Total fish yield was estimated to be 26.4 t km^-2 yr^-1. Reef and reef-associated fish species comprised about 85% of the total yield and was dominated by caesionids (33%) and acanthurids (28%) caught by hookah and set gill net. Hookah contributed highest yield from Nablag patch reef. Reef and reef-associated fish yield was estimated to be 22.44 t km^-2 yr^-1. This is almost four times the 1992 estimate of 5.8 t km^-2 yr^-1 when community-based management efforts were initiated by the SEAFDEC Aquaculture Department to sustain the coral reef fisheries in Malalison Island.

Mass mortality occurred in 34-day old larval orange-spotted grouper Epinephelus coioides reared at a hatchery in the Philippines with clinical signs such as anorexia and abnormal swimming behavior. Histopathology of moribund fish demonstrated marked vacuolation of the brain, spinal cord and retina. Cytopathic effects were observed in SSN-1 cells inoculated with the tissue filtrate of affected grouper. Electron microscopy revealed non-enveloped virus particles measuring 20 to 25 nm in diameter in the cytoplasm of degenerated SSN-1 cells. Piscine nodavirus (betanodavirus), the causative agent of viral nervous necrosis (VNN), was detected in the affected tissues and SSN-1 cells inoculated with the tissue filtrate of affected fish by RT-PCR. This is the first record of VNN in the Philippines.