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.

The effects of three levels of stocking density (0.5, 1.5 or 3.0 m⁻²) and monosex culture (male or female) on the growth, apparent feed conversion ratio (FCR), survival, and production of mixed species of mud crabs, Scylla serrata and S. tranquebarica, were investigated. The juvenile crabs were stocked in 150 m² earthen ponds with Gracilariopsis bailinae as shelter and fed a mixed diet of 75% fresh mussel flesh and 25% fish bycatch. There was no interaction between stocking density levels and monosex culture (P<0.05) so that data were pooled for each sex or stocking density treatment. Highest survival and the most efficient FCR were obtained from stocking density of 0.5 m⁻² (P<0.05). Crab growth rates in different stocking densities were not significantly different (P>0.05). Male crabs attained significantly higher (P<0.05) final weight and specific growth rate (SGR) than female crabs. However, final crab length, width, FCR, survival, and production were not significantly different between male and female crabs (P>0.05). Highest return on investment (ROI) and lowest production cost were obtained from 0.5 m⁻². Partial budgeting analysis showed that no net benefit accrued from stocking beyond 1.5 m⁻². Both male or female monosex cultures gave high net revenue and ROI of more than 100%. Results suggest that the culture of male or female mud crabs at 0.5–1.5 m⁻² is economically viable but male monosex culture is more profitable.

Intensified production of fish involves stocking at high densities and the use of artificial feeds. These practices result in eutrophication and environmental degradation mainly because of feed wastage and fish excreta. To minimize waste, the maximum amount of feed consumed by fish must be known. Food consumption and utilization, however, may vary with the size and physical condition of the fish. Milkfish Chanos chanos Forsskal and some hatchery-produced fish, such as seabass Dicentrarchus labrax L. have been observed to have morphological defects that could affect normal food intake and utilization. Jaw abnormalities in hatchery-bred milkfish interfere with feeding and result in very slow growth. In the Philippines, milkfish fry for production in ponds and cages are caught from the wild or produced through artificial spawning. Studies have been conducted to estimate the feed ration for milkfish reared in brackish water ponds where natural food contributes significantly to the nutrition of the fish. In ponds and marine cages, where fish are largely dependent on artificial feeds, daily feed ration has to be estimated. This study determined the maximum feed ration for different sizes of wild and hatchery-bred milkfish based on assimilation of energy.

The yield (%) and viscosity (cps) of alginate from Sargassum carpophyllum, S. ilicifolium and S. siliquosum collected along the inter- and subtidal zones of Currimao, Ilocos Norte were determined monthly for a period of one year. Results show that each species demonstrated an individual pattern of alginate characteristics which is significantly influenced by the collecting zone, fertility state, and collecting month (P < 0.05). Positive correlations were observed in alginate yield and viscosity with species and fertility states. Among the three species, S. ilicifolium is the best species for alginate production for the food industry based on viscosity characteristics, followed by S. siliquosum and S. carpophyllum.

The process required and options for water treatment in recirculating systems have been clearly identified. The four most critical processes are: (1) solids removal, to take out fecal waste, uneaten feed, excess bacterial biomass, and other solids also reducing biochemical oxygen demand (BOD) in the process; (2) biological filtration or biofiltration, primarily nitrification to convert toxic ammonia and intermediate from nitrite to nitrate; (3) gas exchange, which includes aeration to ensure sufficient oxygen supply for fish and biofiltration, and degasification to stripe carbon dioxide; and what may be called (4) ion balance, primarily to maintain pH and alkalinity and prevent the buildup of nitrate, dissolved organic, and other substance. System with extended hydraulic retention times must generally have an alkalinity replenishment regime to compensate for the alkalinity-consuming nitrification process. Additional treatment processes include denitrification (nitrate removal, which helps to augment alkalinity), ozonation (to remove color, organics and BOD; also sterilizes), ultraviolet (UV) sterilization (for disease/pathogen control), and foam fractionation (to remove dissolved organics surfactants). Heaters and/or chillers may be provided for temperature control. It must be emphasized that while the processes and equipment are provided for specific purposes, a complex interrelationship exists in recirculating systems. Recirculating system components and sizing criteria vary widely, and are mainly provided to comply with specific production needs. A combined upflow and fluidized sand filter design that is applicable and easily adaptable to any system that may be recirculated is presented. Design and operational criteria are provided, as applied to a milkfish broodstock system. In general, for better management and control of water quality, to conserve water and energy and reduce wastewater, and to essentially provide for complete treatment of wastes and mitigate its impact on the environment, a high degree of water recirculation is recommended.

Penaeus monodon postlarvae (PL1, PL5, PL10, and PL15) and juveniles (0.2 and 2 g mean weights) were acclimated gradually within 6 h to test temperatures of 22°, 28°, and 33°C. After 24 h, the postlarvae were abruptly transferred to salinity levels of 8, 16, 24, 32, 40, or 50 ppt, and juveniles to 0, 4, 8, 16, 20, 24, 28, 32, 40, 50, or 60 ppt. All test animals were previously reared in 32 ppt sea water at a temperature of 27-29°C. Survival rates were compared after four days for PL1, PL5, and PL 10, and 10 days for PL 15. Tests for juveniles lasted seven days. Length and total (TPI) or mean (MSI) population stage indices were compared for postlarvae. Survival rates of postlarvae and juveniles were generally lower at 33°C. Length and MSI of postlarvae were higher at 33°C than at 22°C. TPI at PL10 and PL15 were not significantly affected by salinity. Optimal salinity ranges for postlarvae and juveniles were identified based on the different parameters measured.

Six semi-purified casein based diets were formulated to contain either a complete mineral mixture (control) or mineral premixes from which a specific test mineral was deleted to obtain phosphorus(P)-free, magnesium(Mg)-free, iron(Fe)-free, zinc(Zn)-free, or manganese(Mn)-free diets. These diets were fed to juvenile milkfish (mean initial weight 2.60±0.08g) for a 22-week experimental period. Final mean percent weight gain ranged from 1022 to 1379% with P-free (1022%) and Fe-free (1066%) diets obtaining a significantly lower weight gain (p<0.01) than the control diet (1270%). Survival was greater than 90% and did not differ significantly among treatments. Upon termination of the growth experiment, milkfish flesh, bones, and combined samples of head, skin, and scales were dissected and analyzed for ash, P, Ca, Mg, Fe, Zn, and Mn content. The deletion of P or Fe from mineral mixture lowered P content in flesh and bone. Zn content in bone of fish was also lowered by exclusion of Zn, Mn, Mg or Fe. The result of this study demonstrated that it is necessary to supplement P and Fe even to semi-purified casein based diets.

The distribution of phytoplankton and zooplankton around three sandbanks (Gootebank, Westhinder and Buitenratel sandbank) off the Belgian Coast was investigated in February 1994. The abundance of phytoplankton taxa was significantly different between the sandbanks. Community analysis using TWINSPAN resulted in a clear separation of clusters corresponding to the different sandbanks. The zooplankton community analysis, on the contrary, showed a rather indistinctive division of the sandbank stations. This was due to the omnipresence of three dominant copepod species (Temora longicornis, Pseudocalanus elongatus and Centropages hamatus). When these species were excluded from the analysis, a clearer distinction between the different sandbanks was found. The observed differences in phyto- and zooplankton species distribution could be explained by the position of the sandbanks. Westhinder is positioned further from the coast than Buitenratel, while Gootebank has an intermediate position. Buitenratel and Gootebank harbour typical coastal plankton communities, while the plankton community over Westhinder is clearly influenced by the Atlantic current penetrating the southern North Sea from the English channel. More phyto-benthic species were found at Buitenratel than at Gootebank, probably because of its limited depth. Thus, the Belgian coastal zone, which is considered as one box in most spatial descriptions of the North Sea plankton, in fact harbours heterogeneous plankton communities at the end of winter.