The survival of milkfish broodstock (body weight range 1–11 kg) was determined until 30 days after handling and transport in open tanks or in sealed oxygenated bags containing chilled sea water (20–25 °C). Maintenance of cool sea water was achieved by the gradual addition of ice chunks or frozen gel packs. A survival rate of 50% after transporting fish at a loading density of 45 kg m⁻³ for 4 h in open tanks was not significantly different from those that were handled but not transported (86%). Similarly, survival rates (67–83%) among broodstock confined for 8 h in chilled sea water at 40 and 60 kg m⁻³ were not significantly different from each other or from a group not subjected to confinement. Nevertheless, low dissolved oxygen (DO) and accumulation of total ammonia–nitrogen beginning 1 h after transport and confinement may be responsible for low survival rates of milkfish in open tanks. In contrast, all milkfish survived 10 h of overland transport in sealed bags with chilled and diluted (28 g L⁻¹) sea water. Likewise, all milkfish survived after being bagged and immediately transferred to a communal rearing tank, or bagged and placed in a styrofoam box for 10 h. Except for total ammonia–nitrogen levels, which increased slightly (0.7–0.8 mg L⁻¹) above background, seawater temperature (20–24 °C), salinity (28 g L⁻¹) and DO (6 to > 20 mg mL⁻¹) titres in transport bags were maintained during the 10-h test. The effectiveness of handling and transporting milkfish broodstock in sealed bags containing chilled sea water was verified in actual field trials. Spawning of sexually mature milkfish subjected to these stressors was not impaired. These results demonstrate that mortalities of large milkfish broodstock can be minimized when fish are handled and transported in sealed oxygenated bags containing chilled sea water.

Juvenile hormone (JH) and serotonin (5-HT) were previously shown to enhance mictic (sexual) female production of the rotifer Brachionus plicatilis in batch cultures. To explore the basis of these effects, experiments were conducted on isolated individuals. JH treatment of maternal rotifers with 5 and 50 µg ml^-1 (18.8 and 187.7 µM) resulted in significantly higher (P < 0.05) mictic female production in the second (F₂) and third (F₃) generations. JH treatment was effective even at a lower food concentration of 7 × 10⁵ cells ml, but it was not effective when free ammonia was added at 2.4 and 3.1 µg ml^-1. Mictic female production was not increased with exposure to 5-HT up to 50 µg ml^-1 (129.1 µM) concentrations. When food level was reduced to 7 × 10⁵ cells ml^-1, however, 5-HT-treated rotifers produced significantly (P < 0.05) more mictic females than the control, particularly in F₃ generation. Mictic female production of 5-HT-treated rotifers did not differ from that of the control with or without free ammonia, but the intrinsic rate of natural increase (r) of 5-HT-treated rotifers at 3.1 µg ml^-1 free ammonia was significantly higher than the control. These results show that juvenile hormone increases mictic female production under optimum and sub-optimum food levels, whereas 5-HT increases both mictic female production at low food level and population growth rate at high free ammonia concentrations. These compounds could be used to manage rotifer cultures and probe the mechanisms controlling the rotifer life cycle as it switches to mictic reproduction.

Feeding, growth and survival of hatchery-bred juvenile abalone, Haliotis asinina (mean initial shell lengths: 32 mm) stocked at 25, 50 and 100 m^-2 of shelter surface area in mesh cages suspended in indoor tanks were determined. Animals were fed the seaweed, Gracilariopsis bailinae, to excess given at weekly intervals. After 250 d, avereage daily growth rate (mean: 122 µm d^-1 shell length, 156 mg d^-1 body weight) was highest in abalone reared at the lowest stocking density (25 m^-2 ). Abalone stocked at 50 and 100 m^-2 had similar growth rates that ranged from 96 to 98 µm d^-1 SL and 123 to 131 mg d^-1 BW). Daily feeding rates of 29 and 30% were not significantly different for abalone stocked at 25 and 50 m^-2, respectively, but were higher than abalone stocked at 100 m^-2. The higher feeding rates of 24-28% day^-1 of abalone in all treatments starting day-129 until day-160 could be due to the onset of sexual maturation as most abalone are already mature at this size. Survival rates were generally high (91-98%) and were not significantly different among treatments. However, body size (range: 59.3 mm SL, 57-58.4 g BW) at harvest was bigger in animal stocked at 25 m^-2 than those stocked at 100 m^-2. Sexual maturation during culture did not hamper growth of abalone. G. bailinae proved to be a sufficient food source for abalone grow-out. A stocking density between 50-100 m^-2 is recommended for tank grow-out of H. asinina.

Salinity tolerance and the effects of salinity on growth, condition factor and chloride cell (CC) densities were evaluated for Lutjanus argentimaculatus larvae during ontogeny. Tolerance of L. argentimaculatus larvae to abrupt changes of salinity from 32 ppt varied with age. Periods to 50% mortality (LT₅₀) were significantly (P<0.05) longer for 0-day-old larvae than for 7-, 14- and 21-day-old larvae. Tolerance of abrupt salinity change increased remarkably, starting on day 28. Although abrupt transfer to test salinities caused substantial mortalities, L. argentimaculatus larvae, regardless of age (0-, 7-, 14-day-old), showed significantly longer LT₅₀ when abruptly transferred to 8 and 16 ppt than for transfers to 24 and 40 ppt (P<0.05). Growth of L. argentimaculatus larvae at 16, 24, 32 (control) and 40 ppt was not significantly different either at the end of the first rearing phase (days 0–21) or second phase of rearing (days 22–50). Survival was significantly lowest at 40 ppt (4.3%) at the end of first phase of rearing (P<0.05). There were no significant differences in survival rates at the end of the second phase of rearing; however, the condition factor (K) of larvae reared at lower salinities was significantly higher than that of fish at 40 ppt (P<0.05). Gill epithelia of 42- and 50-day-old larvae showed increasing density of CC with increasing salinity.

The growth of river catfish Mystus nemurus (Cuvier & Valenciennes) larvae fed four isocaloric diets (4200 kcal kg⁻¹) with different protein levels during weaning was determined. Diets containing 45, 50, 55, and 60% protein were formulated by linear programming using amino acid profiles based on that of 2-day-old river catfish larvae. Artificial diets were fed to the larvae beginning at day 5 after being initially fed Artemia nauplii for 4 days. The larvae thrived solely on artificial diets from day 8 to day 16. On the other hand, the control larvae were fed Artemia nauplii from day 1 to day 16. Results of the feeding trial showed that growth and survival of M. nemurus larvae given the diet containing 60% protein were high and comparable to those of the larvae given only live food (control). Larvae fed the 55% protein diet had significantly lower growth and survival than the larvae on the control and 60% diets but significantly higher growth and survival rates than did larvae fed with 45 and 50% protein diets. Carcass moisture and total lipids after 16 days of feeding did not differ significantly (P > 0.05), but body protein increased with increasing dietary protein. Body protein of the control larvae was similar to that of larvae given the 60% protein diet.

The economic feasibility of four grow-out diets for the Asian catfish Clarias macrocephalus was evaluated on a 1000 m²/crop basis. Hatchery-bred catfish juveniles with mean body weight (MBW) of 3.6 g and mean total length (MTL) of 7.8 cm were stocked at 10 fish/m². Laboratory-formulated diet with 20% crude protein (CP; Diet 1) resulted in net losses. Laboratory-formulated diet with 34% CP (Diet 2), commercial feed pellet with 29% CP (Diet 3), and a mixed diet of blanched chicken entrails (80%) and rice bran (20%) with 32% CP (Diet 4) gave acceptable return on investment (ROI) of 131-326% and return on operating capital of 52-71%. Culture of Asian catfish fed Diet 2, however, attained higher net profit before tax per 1000 m²/crop, ROI (326%), and has the lowest payback period on investment (0.3 yr) or operating capital (1.4 yr) compared with using Diets 3 and 4. Partial budget analysis showed that higher net benefit can be earned by using Diet 2 as feed for C. macrocephalus compared with using Diet 4. Sensitivity analysis done by increasing in feed cost by 20% and decreasing the selling price of fish by 20% showed that ROI were 107-262% and 46-159%, respectively and return on operating capital of 42-57% and 18-35%, respectively. Payback period on investment were 0.4-0.9 yr and 0.6-1.9 yr, respectively while payback period on operating capital were 1.7-2.2 yr and 2.7-4.7 yr, respectively. Results suggest that C. macrocephalus culture is economically feasible with Diets 2, 3 and 4 as feed but the use of Diet 2 is more profitable.

This study aimed to develop nutritionally balanced and costeffective processed diets for milkfish larvae (Chanos chanos). Two larval diets (feed A and feed B) were formulated and prepared to contain 45% protein and 10% lipid. Several larval diet preparations were tried such as microbound/unpelleted (freeze-dried), microbound /pelleted (oven-dried) and microbound/flaked (drum-dried) and assessed in terms of feed particle size and buoyancy, water stability and feed acceptability. The preparation that gave the best particle size and buoyancy as well as good water stability was prepared as the microbound diet (using K-carrageenan as a binder) and flaked using a drum drier. A series of feeding experiments were conducted to determine the growth and survival of milkfish larvae reared on various feeding schemes using these processed larval diets which were fed either solely or in combination with live feed. Larvae in control treatments were reared on live foods such as Brachionus plicatilis and Artemia nauplii. Larvae were observed to ingest the diets, indicating that the feeds had suitable physical characteristics and were attractive to the larvae. The overall results of the feeding trials showed that the artificial diets could be fed to milkfish larvae in combination with Brachionus rotifers starting on day 2 or day 8, and could be fed alone starting from day 15. These promising results would reduce the dependence of milkfish larvae on live feed and would have significant economic benefits in the form of simplified milkfish hatchery procedures.

We report the isolation, cDNA cloning, and growth promoting activity of rabbitfish (Siganus guttatus; Teleostei; Perciformes; Siganidae) growth hormone (GH). Rabbitfish GH was extracted from pituitary glands under alkaline conditions, fractionated by gel filtration chromatography on Sephadex G-100, and purified by high-performance liquid chromatography. The fractions containing GH were identified by immunoblotting with bonito GH antiserum. Under nonreducing conditions, the molecular weight of rabbitfish GH is about 19 kDa as estimated by SDS–PAGE. The purified hormone was potent in promoting growth in rabbitfish fry. Weekly intraperitoneal injections of the hormone significantly accelerated growth. This was evident 3 weeks after the start of the treatment, and its effect was still significant 2 weeks after the treatment was terminated. Rabbitfish GH cDNA was cloned to determine its nucleotide sequence. Excluding the poly (A) tail, rabbitfish GH cDNA is 860 base pairs (bp) long. It contained untranslated regions of 94 and 175 bp in the 5′ and 3′ ends, respectively. It has an open reading frame of 588 bp coding for a signal peptide of 18 amino acids and a mature protein of 178 amino acid residues. Rabbitfish GH has 4 cysteine residues. On the amino acid level, rabbitfish GH shows high identity (71–74%) with GHs of other perciforms, such as tuna, sea bass, yellow tail, bonito, and tilapia, and less (47–49%) identity with salmonid and carp GHs.

Different sizes of the mangrove mud clam Anodontia edentula were collected from the mangroves in Brgy. San Roque in Estancia, Iloilo, central Philippines, and the mantle, gill, and foot tissues were analyzed for elemental sulfur content. Mangrove mud (substrate) was also analyzed for total sulfur content to establish the possibility of clam-bacteria symbiosis in this lucinid clam. Sulfur analysis showed highly significant (p <0.0001) amounts of elemental sulfur in the gills (247.64 ± 63.28 μmoles/g FW) compared with the quantities observed in the mantle (0.84 ± 0.22 μmoles/g FW). Elemental sulfur was absent from the foot tissues. Results also showed a significantly (p <0.05) decreasing elemental sulfur from the newly collected clams (mean = 461.18 μmoles/g FW) compared to those reared in the laboratory (mean = 159.08 μmoles/g FW: with mangrove mud substrate; mean = 45.18 μmoles/g FW without substrate), which were analyzed weekly until week 3, indicating that stored elemental sulfur is being utilized by the bacteria in the absence of sulfide. Total sulfur content of mangrove mud in situ was higher than that used us substrate in the experiment; where there were no significant differences from initial to final readings. This shows that mangrove mud in situ is linked to a steady sulfur source.

The mangrove clam Anodontia edentula is highly prized in the Philippines for its flavor and large size. Because this infaunal species is found down to one meter deep in mangrove areas, harvesting the clam reportedly damages mangrove stands. To evaluate such reports, a survey of collection methods was undertaken in Panay and Guimaras, central Philippines in August 1997-December 1999. Host to chemosynthetic bacterial symbionts that utilize sulfide as energy source, A. edentula are strategically situated in sulfide-rich anoxic substrates but also gain access to oxygenated seawater through a ventilation burrow or tube. By locating the opening of this burrow, collectors can detect the presence of a buried clam and harvest it nondestructively with a blade or bare hands. In contrast, the indiscriminate tilling of wide mangrove areas can damage mangrove plants. Most collectors were 40-45 years old with 22-30 years collection experience, married with 5-7 children, and had low educational attainment. They sold clams directly in the local markets or through middlemen (to restaurants and beach resorts); sales provided from 10% to 100% of daily family income. Collectors complained of decreasing clam sizes and numbers and the physically strenuous work of collecting.