European sea bass (Dicentrarchus labrax) fry vaccinated orally via bioencapsulation in Artemia nauplii or by bath method exhibited better performance than control fish in terms of growth, food conversion and resistance to stress. The comparable survival between vaccinated and non-vaccinated animals suggests that vaccination methods are not stressful. The present study shows that oral vaccination can be used to enhance growth in fish fry.

The weight-specific ammonia excretion rate of sea bass (Lates calcarifer) fry in fresh water is higher than that of those in sea water. The allometric equation \(y = 24.426 \times ^{-0.4714}\) best describes the relationship between the ammonia excretion rate (y, in µg total \(NH_{3}-N/g/hour)\) and body weight (x, in g wet weight) for fry in fresh water and \(y = 19.891 \times ^{-0.6712}\) for fry in sea water. The ammonia excretion rate of sea bass fry in fresh or sea water did not significantly increase or decrease during prolonged starvation. The pre-feeding ammonia excretion rate of sea bass subadults in fresh water was similar to those in sea water. The ammonia excretion rate of both groups ranged from 3.86 to 4.13 µg total NH₃-N per g per hour. Half an hour after feeding, ammonia excretion rates rose to a significant level over pre-feeding values in both freshwater and seawater-adapted subadults. Both groups also showed the same peaks that were 7.5 times higher than pre-feeding levels 3 hours after feeding. By 10 hours after feeding, the ammonia excretion rate of both groups had returned to pre-feeding levels.

The paper reviews and evaluates shrimp pond culture in the Philippines and its ecological and socioeconomic effects. The intertwined histories of the country's mangrove forests and culture ponds are treated in depth; brackishwater aquaculture and the different shrimp culture systems are described. Intensive farming is discussed in terms of feed and water requirements, chemical inputs and waste production, and the attendant organic and nutrient overloading, longevity and toxicity of chemicals, development of antibiotic resistance, and introduction of exotic species. Most of the discussion is based on the Philippine experience, but relevant case studies from other shrimp‐growing countries, notably Thailand and Indonesia, and also from salmon cage culture in the temperate zone, are included. Ecologically and economically more viable, semi‐intensive culture is recommended as the key to the long‐term sustainability of the shrimp industry. Because the greatest impact of brackishwater pond culture (including shrimp farming) is the loss of mangrove habitats and their varied goods and services, massive reforestation of degraded areas should be undertaken. Other recommendations are the promotion of environmentally sound aquaculture technologies, e.g., seaweed and mollusc culture and the integrated forestry‐aquaculture‐fisheries management of mangrove plantations (tumpang sari) in coastal areas; enforcement of existing laws that protect remaining mangroves; and promulgation of new laws to regulate water use and waste disposal. Areas for future research include the prevention and control of pond wastes and shrimp diseases, and refinements of the Indonesian tumpang sari for adoption locally.

The effect of two levels of stocking density (5 and 7 m^-2) and the two types of feed [trash fish only (TF), and a mixed feed (MF) (mixture of 25% trash fish and 75% commercial pelleted feed)] on the growth, apparent food conversion ratio (FCR) and survival of the thirty-day old sea bass fry were investigated. The fry were stocked in 144 m² earthen ponds and reared for 45 days. The result showed that, in general, the lower density increased but the MF decreased the survival, specific growth rate (SGR) and FCR of sea bass fry. Statistically, there was no significant effect of treatments on survival, whereas SGR and FCR affected differently. With TF, both were higher at 5 m^-2 and lower at 7 m^-2. With MF, SGR was higher at 5 m^-2 than at 7 m^-2 and the FCR was most efficient at 5 m^-2 than at 7 m^-2. There was no interaction between the type of feed and the stocking density. For the efficient utilization of feed, the TF+5 m^-2 treatment was the best for rearing seabass to fingerlings.

Wild Epinephelus suillus (Valenciennes) were collected in 1989 to early 1990. To monitor natural spawning in captivity, 6 mature females (3.5–5.0 kg) and 4 mature males (7–12 kg) were transferred to a 4.6×4.6×2 m concrete tank, and one mature female (5.3 kg) was paired with two spermiating males (6.0–6.5 kg) in a 4×4×3 m floating net cage. Spontaneous spawning occurred successively 5–17 times a month from July 1990 to June 1991 (except in May) in the tank and 5–10 times a month from July to October 1990 in the floating net cage. The number of eggs collected, mean fertilization rate and mean hatching rate in the tank and the floating net cage each month ranged from 0.5–15.8 million and 2.3–3.9 million, 67–88% and 72–89%, and 2–81% and 29–68%, respectively. The onset of the monthly spawning cycle in both holding systems was observed over a period of 3 days either before or after the last quarter moon. The results indicate that a minimum number of E. suillus broodstock are required for a year-round supply of fertilized eggs.

Growth, daily ration, and gastric evacuation rates of milkfish (Chanos chanos) that fed on natural food and supplement diet were evaluated. Milkfish fingerlings (5.5g) were stocked at 1.5 fish/m² in ten 12 m² concrete tanks layered with 15-cm thick earthen bottoms. All tanks were regularly fertilized (16–20–0 and chicken manure) to maintain natural food production; 4 of the tanks additionally received a supplemental diet containing 34.3% protein and 4290 kcal/kg gross energy. Estimates or daily ration (based on dry weight of stomach contents) were calculated using the Elliot and Person (1978) and Eggers 1977) models. Gastric evacuation rate was lower in fish that fed on natural food (1.57) compared to fish fed a supplemental diet (1.79). Consequently, the lower rate resulted in lower food intake and slower fish growth. When fish were provided a high quality supplemental diet, daily rations for fingerlings (35 g) to marketable size (116 g) ranged approximately from 0.60 to 19.68 kcal/fish/day. The deviation in daily ration (kcal/fish/day) from the above estimates may indicate the insufficient quantity of dietary energy taken by fish from natural food alone, which could be provided by supplemental diet.

The 28-hectare tilapia cage culture that occupied the 104-hectare Sampaloc Lake, a crater lake, shifted to intensive method in 1986 when tilapia growth slowed done at the beginning of 1982. Thus, commercial feeds became the main source of allochthonous organic matter in the lake. Total feeds given annually for the 28-hectare cage culture at 3 croppings per year amounted to 5250 tons. At feed conversion ratio of 1 : 2 a significant portion of the feeds given ended as organic wastes in the lake. In 1988, tilapia cage operators began experiencing their worst occurrences of fishkill, worth millions of pesos. An assessment of the dissolved oxygen condition of Sampaloc lake in late 1989, 1990 and mid-1991 showed ominous trends which might adversely affect the use of Sampaloc lake for fishery.

The use of live microalgae for food during the early stages of the life cycle of shrimp larvae is considered essential. The microalga Chaetoceros calcitrans was mass produced at the Aquaculture Department of the Southeast Asian Fisheries Development Center (SEAFDEC/AQD) using the multistep method. The alga was grown in batches using successively larger containers. A cell density of 2.65 × 10⁶ cells/ml was obtained from the final 4-day culture of C. calcitrans. Production cost using this method was P715.50/ton (US$ 1.00=25 Philippine pesos). The minimal costs involved in this method make it an affordable technique for the mass culture of microalgae.

Hatchery-reared Penaeus monodon postlarvae were cultured in ponds until they attained adult size. Thereafter, the shrimps were transferred to concrete broodstock tanks for maturation. During the culture period, the morphological changes of the ovary in relation to the development of the external genitalia and other quantitative parameters were examined. Based on histology, primordial germ cell and chromatin nucleolus in the early stages of ovarian development were reported in addition to the stages that have been described earlier on adult specimens, thus completing the description of ovarian development on P. monodon. Females with ovaries at the perinucleolus stage can be impregnated as long as the thelycum is structurally developed to receive the spermatophores. Females with cortical rod stage ovaries either spawned or resorbed their eggs before molting, indicating that the molting cycle overrides reproductive activity in first-maturing females.

The total lipid content and fatty acid composition in the hepatopancreas, muscle and gonad of ablated Penaeus monodon females at ovarian maturation Stages I to V were examined. The lipid content was highest in the hepatopancreas, 22.5% to 34.9% dry wt. There was no marked variation with maturation stage in muscle lipid levels. Ovarian lipid content more than doubled the initial value of 7.5% at commencement of maturation Stage II, and progressively increased to a maximum of 21.9% at full maturity (Stage IV), corollary to a rise in hepatopancreas lipid. The findings suggest lipids are stored and utilized for gonadal development and spawning. Fatty acid profiles in the tissues showed a predominance of 20:4n-6, 20:5n-3 and 22:6n-3 polyunsaturated fatty acids (PUFA). The characteristically high levels of PUFA in mature shrimp ovaries and presence in spawned eggs are indicative of their metabolic and physiological importance in penaeid shrimp reproduction.