Aerobic bacterial flora of eggs and larvae of milkfish, Chanos chanos, was investigated. Microflora in the incubating water of egg, rearing water of larvae, water source, and larval food was also analyzed. Aerobic bacterial flora of milkfish eggs was largely influenced by the bacterial flora in the incubating water. Both in eggs and in the incubating water Pseudomonas species were the dominant bacteria. During milkfish larval rearing, intestinal aerobic bacterial flora was examined at days 1, 3, 7, 10, 15, 18, and 21. Bacterial number in the larvae and rearing water significantly increased during the culture period up to day 18 but dropped significant at day 21. Pseudomonas species were detected from yolk-sac larvae (day 1) as the dominant bacteria, similarly to the normal flora in the rearing water. However, intestinal bacteria were predominated with Vibrio species when the yolk-sac was absorbed on day 3. Larval rearing water, water source, and larval food contained predominantly Pseudomonas species.

In this study, the developmental stage, iodine concentration and exposure time that will reduce the bacterial load without decreasing the hatching rate for the disinfection of grouper (Epinephelus coioides) egg were established. Results of the study showed that the best stage to disinfect grouper egg is at late neurula stage where the embryo shows twitching movement. The effective and safe concentration that will reduce bacterial load but will not decrease hatching rate for the disinfection of grouper egg is 7.5 ppm free iodine for 10 min. Total bacterial count of eggs disinfected with 7.5 ppm free iodine for 10 min (8.99 x 10² cfu/20 eggs) is significantly lower than the unrinsed/undisinfected eggs (1.99 x 10⁷ cfu/20 eggs).

The need for a chemotherapeutant used specifically for fish disease became increasingly apparent with intensive fish culture practices, and with the possibility of bacterial resistance against drugs used for human and animal medicine (Austin 1985). With this in mind, Nifurpirinol (trade name Furanace; P-7138) was developed by the Dainippon Pharmaceutical Co., Ltd., Japan, and is currently manufactured in the United States as Prefuran. Studies have proven that the drug is effective against bacterial and fungal pathogens in a wide variety of aquatic animals. Most of the Nifurpirinol studies done in the past have dealt on its antimicrobial activity, tissue uptake, and effective treatment levels ranging from 0.5-2.5 mg/L. The 96-hr median lethal concentration (LC50) to channel catfish (Ictalurus punctatus Rafinesque) has also been determined at 0.945-1.90 mg/L, and at 1.70 mg/L for milkfish, Chanos chanos Forsskaal. However, there have only been two studies that have examined the histological effects on treated fish. Histopathologically, Mitchell et al. (1978) found hypertrophy and hyperplasia of the lamellar epithelium in channel catfish gills exposed to 0.5 mg/L for 4 d or longer at 24 plus or minus 2 degree C, while Amend and Ross (1970) working at 21 plus or minus 1 degree C observed no apparent changes in the gills of coho salmon (Oncorhynchus kisutch) exposed intermittently to 1 mg/L of Nifurpirinol. This paper describes the histological changes observed in the gills of milkfish fingerlings used in static, 96-hr Nifurpirinol toxicity tests. Milkfish was used because of its economic importance as a widely cultured food fish in Asia. The gills were chosen as target organs.

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 (α = 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. The higher growth at the 4% feeding level could be due to the higher amount of amino acids available for protein synthesis. Higher energy assimilated by milkfish at higher feeding rate demonstrates that energy supply also influences growth. Partial budgeting analysis shows that bigger profits can be earned by using a 24% protein diet with balanced amino acids at a feeding rate of 4% of body weight. The greater amount of feed given at higher rate can be compensated by faster growth and higher production.

Small (5–10.9 mm carapace length), medium (11–15.9 mm), and large (16–20.9 mm) juveniles of Metapenaeus anchistus, Metapenaeus sp., Penaeus monodon and P. merguiensis were stocked individually in glass tanks provided with sand substrate, sea water, artificial bamboo shelter, aeration and food. The seven activity types (recorded for each shrimp hourly for 24 h) were classified as below (burrowing) or above substrate (swimming, walking, stationary, in shelter, feeding and cleaning). Shrimp juveniles exhibited a strong diel periodicity — emergence and activity at night and burrowing in the day. The chi-square test showed that type of activity (above/below substrate) was associated with period (light/dark). Diurnal burrowing was greater among Metapenaeus than Penaeus; inversely, above substrate activities were more frequent for Penaeus species compared to Metapenaeus. Feeding was the major above substrate and nocturnal activity for M. anchistus, Metapenaeus sp. and P. monodon. Only P. Monodon used the shelter consistently. Frequency of the 7 activity types was dependent on juvenile size for Penaeus, e.g., the preference for shelters shifted to burrowing with increase in size in P. monodon. Results are discussed in relation to the importance of mangrove habitats in providing shelter to penaeids, in particular the mangrove-associated P. monodon and P. merguiensis.

The effects of animal size and feeding frequency on the foregut evacuation rates by Cherax quadricarinatus, that fed voluntarily on pellet food (meal size eaten, 1.3–1.4% body weight), were determined using a modified serial slaughter method. Evacuation rates did not differ significantly between size-groups (medium, large) and between feeding frequency-groups (fed daily, fed every second day). However, models that best described the evacuation process were different for each group (i.e., linear model for the crayfish fed daily, arcsine model for those fed every second day). This variation indicates the potential for a crayfish to regulate its digestion processes according to food availability. Faecal production rates did not differ significantly between feeding frequencies. Return of appetite, measured in terms of voluntary feed intake at bi-hourly intervals following satiation meals, was shown to be related to the foregut evacuation process, but it was probably the supply of fresh gastric fluid after ca. 4 h following a meal which mainly influenced the increase of appetite. The rapid return of appetite in crayfish implies that they can resume feeding while a considerable proportion of an earlier meal is still being processed in the foregut. This indicates that crayfish are capable of optimising the frequency of feeding during active foraging periods.

Acid sulfate soil formation was observed experimentally during leaching of pyritic soil material. Pyritic soil was saturated with distilled water in glass columns and treated under waterlogged and drained conditions. Waterlogged was inundated and had overlying water of 2-cm depth above soil surface. Temporal changes of various chemicals and physical characteristics of the soil and leachates were determined at 10-day leaching intervals. Results showed that strong acidification of soil in drained column but not in waterlogged was due to pyrite (FeS₂) oxidation and the consequent production of sulfuric acid (H₂SO₄). As oxidation progressed, acidification influenced the pH, and increased the solubility of aluminum (Al) and iron (Fe). The loss of potassium (K) and sulfur (S) fractions was also enhanced by acidification. Strong acidic condition in drained columns slightly changed the texture of the soil to more clay, but was not enough to alter the mineral composition of the soil. Periodic leaching was found effective in increasing soil pH, but some essential nutrients were also removed, thus, the need for fertilization scheme during amelioration. In prospective ponds, pyritic soil should be tilled and dried for 2–3 weeks, then flushed and drained repeatedly until pH > 5 is obtained. Repeated lime incorporation should be done in the amelioration until high pH values are obtained. In existing ponds, formation of acid sulfate soil could be avoided by not excessively turning and exposing the pond bottom.

Rapid Rural Appraisal (RRA) was conducted in the fishing village of Lakaran, in the municipality of Dumangas, Iloilo province to identify the resources, livelihood, problems, opportunities, and socioeconomic condition of the villagers prior to the conduct of farmer participatory research on mussel farming. RRA tools such as the construction of the village transect, seasonal calendar and wealth ranking were used.

The effect of tank color on rotifer ingestion, early growth and survival of milkfish larvae was assessed. The larvae were stocked at 30/L in 200-L fiberglass tanks coated black or unpainted (tan). Larvae were fed rotifers at densities of 5, 10, and 15/ml. Growth and survival were higher in black tanks than in tan tanks. Rotifers ingested were also higher in larvae reared in black tanks. In black tanks, the survival of the larvae was enhanced at high rotifer density of 15/ml. Rotifer ingestion and growth of larvae improved at higher feeding levels.