The sensitivity of grouper Epinephelus coioides eggs to handling stress at different stages of embryonic development was investigated. Naturally-spawned grouper eggs in floating net cages were collected and handled at the early cleavage, blastula, gastrula, neurula, and eyed stages. Egg viability, hatching rate and percentage of normal larvae were significantly higher (p<0.05) in eggs collected and stocked at the eyed stage than in all other stages. An increasing sensitivity to handling stress was observed in eggs from early cleavage to gastrula, as manifested by the decreasing percentage of viable eggs, hatched, and normal larvae. Sensitivity to handling stress decreased when development reached the neurula and eyed stages. Hatched larvae from eggs handled during the blastula and gastrula stages had high mortalities during the first 3-24 hours after stocking. The results of this study show that grouper E. coioides eggs are most sensitive to handling stress during the early cleavage to gastrula phases. The results imply that harvesting or collection of grouper eggs is best done after neurulation, when the embryo has already formed optic vesicles (eyed stage), to increase egg viability and the hatching rate. It will also minimize mortalities and the occurence of abnormal larvae.

Milkfish farming in the Philippines has a long history and great importance, being widely regarded as the way to domestic food security. But the industry has faced new challenges in the past decade, with the advent of many other farmed aquatic species, mostly cash crops and "export winners," and with the increased pressure to intensify production in brackishwater ponds and in marine pens and cages. There are no up-to-date government statistics on the area and production of marine pens and cages, but industry insiders estimate a yearly production of about 25,000 mt of sea-grown milkfish in 1996 - 1998, mostly from Pangasinan, but also from Quezon, Davao, Cebu, Bohol, Panay, Samar, and Negros. High yields (2 -38 kg/m³) were made possible by very high stocking rates (3 -75 fingerlings/m³) and feeding rates (2-4 kg feed per kg of fish). The high production costs and the pollution from feed wastes and fish metabolites have stopped most operations within 1 - 2 years. This paper examines the trends and problems in milkfish farming in marine pens and cages, and discusses the ecological limits and the projected ecological footprint of this farming system. Milkfish farming in marine pens and cages, as presently practised, is not the magic solution to the fish deficit in the Philippines and is not an appropriate technology to promote on a wide scale. The required investment is enormous. Properly made pens and cages set up in suitable clean-water locations cost much. The ability of milkfish to ensure domestic food security is negated by the use of fishmeal-based feeds. Fish feeds use up fish meal and other fisheries and agriculture products used by people and other sectors. If marine pens and cages must be promoted, integrated coastal area management, an informed precautionary approach, better infrastructure, and improved feeding management are important to ensure sustainability.

This paper presents a case study of time use and contribution to the household income of men, women, and children in 12 households in a fishing village in Panay Island, central Philippines. The study highlights the differential impact of poverty on men and women and provides a glimpse of the intrahousehold dynamics within poor fishing households. Findings in previous studies in both industrialized and developing countries that women work longer hours than men were corroborated. Women contribute at least 22% to the household cash income and 40% of the value of unpaid labour. Their contribution to the household cash income becomes larger than that of men's when the value of livestock is computed. Women's daily participation in productive activities, such as fish vending and shucking oyster and mussel, unwittingly puts them in a position of being environmental recorders and verifiers of the state of fishery resources. Because they are burdened with the responsibility of making ends meet, they are also confronted with the challenge of realizing the dream of sending their children to university to enable them to escape poverty. This alone makes women one of the strongest stakeholders in the sustainable development of fishery resources.

Although many fisheries stocks have declined precipitously throughout the world, fish farming--and especially shrimp and salmon farming--has boomed. The increasingly large scale of these enterprises is now having unforeseen ecological consequences on ocean resources through habitat destruction, effluent discharge, exotic species introductions, and heightened fish catch for feed use. Ending unsustainable production practices will require reorienting regulatory policies and fiscal incentives in shrimp- and salmon-producing counties, and enhancing restrictions on environmentally unsound practices.

A total of 4845 penaeids belonging to nine species—Metapenaeus anchistus, M. ensis, M. moyebi, M. philippinensis, Penaeus merguiensis, P. monodon, P. semisulcatus, P. latisulcatus and Metapenaeopsis palmensis—were collected by pocket seine monthly over 13 months from mangrove and non-mangrove sites in Guimaras, Philippines. The restricted distribution of the three dominant species—M. ensisandP. merguiensisto the brackish water riverine mangrove, andM. anchistusto the high-salinity island mangrove and tidal flat—is probably related to different salinity and substrate preferences. Abundance and size composition of the major species suggest a strong nursery role for the riverine mangrove (high juvenile densities, relatively small sizes year-round), limited nursery use of the island mangrove (fewer shrimps, larger size ranges, presence of maturing females) and a non-nursery use (e.g. foraging) in the tidal flat. Penaeid recruitment to the river had two peaks in November and May when the average salinity was ∼20 (Practical Salinity Scale) and water temperatures were high (30–31 °C). The spatio-temporal pattern of penaeid species in Guimaras shows partitioning across habitats and seasonal recruitment influenced by physical and biological factors.

Quantification and characterization of bacterial flora in the hepatopancreas (hp) of pond-reared Penaeus monodon juveniles affected with luminous bacteria were conducted in 1994 and 1995. Shrimp samples were taken from 23 grow-out ponds, 14 of which had disease outbreaks. Luminous bacterial (LB) load of the shrimps' hp with (mean=2.4×10¹ colony forming units (CFU)/hp) and without (mean=0.3×10¹ CFU/hp) disease outbreaks were comparable during the first 15 days of culture (DOC). During disease outbreaks at 18 to 32 DOC, however, LB load of affected shrimps (mean=9.0×10⁴ CFU/hp) were higher than healthy shrimps (mean=7.0×10¹ CFU/hp). At 50 to 60 DOC, levels of LB were comparable in older shrimps with or without disease. Total viable and presumptive Vibrio counts were also comparable in both shrimp samples from 1 to 60 DOC. Characterization of the 172 bacterial isolates collected showed that most (90.12%) were Vibrio species dominated by V. harveyi (27.91%), V. splendidus II (13.37%) and V. parahaemolyticus (10.46%).

Severe mortalities due to luminescent vibrios occurred in pond-cultured Penaeus monodon juveniles particularly in the first 45 days of culture. Luminescent vibriosis epizootics led to reduced shrimp production due to mortalities and slow growth of affected stocks. Monitoring of bacterial population in the rearing water of several ponds was conducted from the time the ponds were flooded with water until 60 days of culture to understand the course of infection. Results showed that the occurrence of mortalities was preceded by a shift of the bacterial profile of the rearing water in infected ponds, notably the dominance of luminescent vibrios. Comparison of bacterial load in the rearing water and water source (river or open sea) showed elevated luminescent Vibrio counts in the former at 12 days to 3 weeks after initial entry of water. Histopathology of affected shrimps showed the hepatopancreas as the target organ of infection where severe inflammatory responses in the intertubular sinuses were seen.

Naturally-spawned milkfish eggs are routinely subjected to physical manipulation during collection and transport. To avoid unnecessary mortalities, sensitivity of milkfish eggs to mechanical shock was determined at different times after fertilization. Shock sensitivity was assessed in terms of egg mortality within 8 h after a free fall over calibrated heights. The LD50 and LD10 (drop height resulting in 50% and 10% mortality) were estimated for 11 stages of embryonic development. The corresponding force (F) imparted to eggs on impact after a free fall was also computed. LD10 estimates (cm) and their corresponding F (erg per egg) showed that shock sensitivity of milkfish eggs was high during cleavage until the early segmentation stage, rapidly declined as segmentation proceeded until the head and tail started to separate from the yolk, but returned to high levels when the embryo begun twitching and the heart beating until near-hatching. To determine the sublethal effects of mechanical shock, C-shaped embryos were subjected to a free fall over varying heights and transported to a hatchery for further incubation and hatching. The effects of varying periods of simulated transport (mobile or stationary periods) were also examined. At C-shaped embryo stage, neither mechanical shock (F, 13–127 erg per egg) nor prolonged shaking (3–9 h) simulating mobile periods of egg transport affected hatching rate, larval mortality, and incidence of deformed larvae. Exposure to still water (unshaken) simulating stationary periods of egg transport, however, tended to lower hatching rate and significantly increased the incidence of deformed larvae and the combined mortalities and deformed larvae. These results indicate that the sensitivity of milkfish eggs to mechanical shock varies during incubation and that C-shaped embryos may be manipulated or transported with minimum risk of injury. Some recommendations are given regarding proper handling and transport of fertilized eggs.

The effects of essential fatty acids (EFA) and vitamin C-enriched live food on growth, survival, resistance to salinity stress and incidence of deformity in milkfish larvae reared in tanks were investigated. Larvae were either fed rotifers cultured on Chlorella sp. and newly hatched Artemia nauplii (control), highly unsaturated fatty acid (HUFA)-enriched rotifers and Artemia nauplii or HUFA+vitamin C-enriched rotifers and Artemia nauplii. Milkfish growth in outdoor nursery ponds was also assessed to compare with growth in indoor tanks. Milkfish fed rotifers/Artemia enriched with HUFA (32–48 mg dry weight, DW) or HUFA+vitamin C (33–45 mg DW) exhibited significantly (P<0.05) higher growth than those given unenriched live food (24–27 mg DW) after 40 days of culture. Growth of milkfish in nursery ponds (albeit lower in stocking density) showed similar trends as those reared in tanks. When subjected to salinity stress (Day 25), mortality of the HUFA+vitamin C-treated fish and HUFA-treated fish were significantly lower (P<0.05) than the control fish. Survival of 26-day old milkfish, however, did not differ significantly (P>0.05) among the treatment groups. Forty-day-old milkfish fed HUFA+vitamin C-enriched live food had significantly lower (P<0.05) incidence of opercular deformity (mainly cleft branchiostegal membrane) (8.4–14.7%) compared with those given HUFA-enriched (15.8–23.5%) or unenriched (27.3–33.5%) live food. Results demonstrated the effect of HUFA enrichment in enhancing milkfish larval growth and resistance to salinity stress but not overall survival. Moreover, HUFA and ascorbate supplementation decreased but did not totally eliminate incidence of opercular deformity in milkfish larvae.

Growth and survival of the larvae of milkfish (Chanos chanos), seabass (Lates calcarifer) and rabbitfish (Siganus guttatus) in 40, 200 and 500 liter rearing tanks were evaluated at day 14. Milkfish larvae survived better (46%) in 500 l than in 200 l (7%) tanks. All larvae died on day 6 in the 40 l tanks. Growth was better in the 200 l tanks than in the 500 l tanks. The survival rate of the seabass larvae was significantly different in the 40 l (47%), 200 l (61%) and 500 l (75%) tanks, but growth was highest in the 40 l tanks. Rabbitfish larvae had the highest survival in 500 l tanks (7%) but the same growth in all tank sizes. The optimum tank size may vary for different fish species. However, small containers are more convenient to use because they require less manpower, are easily manipulated and more cost- effective.