The effects of antibiotics on the external deformities, growth and survival of mud crab Scylla serrata larvae and juveniles were determined. Zoeae were exposed to oxytetracycline (OTC) (0, 3.0, 6.0, 9.0, 12 mg L^-1) and furazolidone (FZD) (0, 0.5, 1.0, 1.5, 2.0 mg L^-1) in the first and second experiments, respectively, until the late megalopa. The crab instars were grown in nursery tanks for 1 month. Larvae survived until megalopa only at 3.0 and 6.0 mg L^-1 OTC or 0.5 and 1.0 mg L^-1 FZD. These four concentrations were run simultaneously in another experiment. Morphological deformities in zoea 5 were bent dorsal, rostral and furcal spines. There was no significant difference (P > 0.05) on the deformities of zoea 5 in 3.0 and 6.0 mg L^-1 OTC and 0.5 and 1.0 mg L^-1 FZD. Significantly (P < 0.05) higher survival and faster growth were attained in 3.0 mg L^-1 OTC and 0.5 mg L^-1 FZD. Deformities observed in juveniles were fused frontal and lateral spines, asymmetrical and depressed tip of abdominal flap and gap between sternites. High percentage occurrence of deformities was observed in the 6.0 mg L^-1 OTC and 1.0 mg L^-1 FZD in the first and third experiments, respectively. There was no significant difference (P > 0.05) observed in the survival of juveniles in OTC and FZD treatments. However, growth was significantly (P < 0.05) faster in lower concentrations of the two antibiotics. The study shows the effects of OTC and FZD in the morphology of mud crab. Therefore, there is a need to eliminate the use of antibiotics and find alternatives.

Starvation and exposure to formalin were investigated as possible stress tests for evaluating the quality of mud crab, Scylla serrata, larvae. For the starvation stress test, newly hatched zoeae stocked in 150-ml containers were either starved or fed rotifers. Similarly, newly hatched zoeae were stocked in containers with seawater of 0 (control), 20, 30 and 40 mg/L formalin for the formalin stress test. The zoeae from the same batches were used for seed production to monitor their performance and validate the results of stress tests. Starvation was found to be unsuitable for larval quality evaluation. However, the impact of initial food deprivation on the newly hatched larvae indicates that feeding immediately after hatching is necessary for mud crab larvae. Exposure of larvae to 40 mg/L formalin for 3 hr appeared to be a reliable and practical method for larval quality assessment as the survival of larvae in the mass production tanks validated the classification of good and poor quality batches in the stress tests. On this basis, a hatchery operator can decide which batch should be cultured further. Finally, there appears to be a link between the quality of larvae and the performance at the megalopa and early juvenile crabs.

A 90-day feeding trial was conducted on milkfish, Chanos chanos with an initial mean body weight of 3.07 ± 0.17 g (mean ± standard error of mean). Six treatment diets were formulated to contain 0 g/kg (Diet 1), 150 g/kg (Diet 2), 25 g/kg (Diet 3), 300 g/kg (Diet 4), 350 g/kg (Diet 5) and 450 g/kg (Diet 6) distiller's dried grain with soluble (DDGS). All the dietary treatments were isonitrogenous (350 g/kg crude protein) and isolipidic (6% crude lipid). Result of the feeding trial indicated that growth rates, feed intake and feed efficiency were not significantly (p > .05) affected by inclusion levels of DDGS by up to 450 g/kg in the feed. Proximate body composition (crude protein, crude lipid, ash, fibre) in fish fed the dietary treatments were not significantly (p > .05) affected as well. The DDGS when used as a milkfish ingredient has a protein digestibility of 910 g/kg, fat disgetsibility of 850 g/kg, carbohydrate digestibility of 750 g/kg and a dry matter digestibility of 520 g/kg Results from the intestinal morphology displayed no apparent pathological changes in the digestive tract of fish fed all dietary treatments. These results indicate that DDGS can be efficiently utilized by milkfish by up to 450 g/kg without negatively affecting performance parameters and intestinal morphology.

Many demersal fish species undergo vertical shifts in habitats during ontogeny especially after larval metamorphosis. The visual spectral sensitivity shifts with the habitat, indicating a change in colour vision. Colour vision depends on sufficient ambient light and becomes ineffective at a particular low light intensity. It is not known how fishes see colour in dim light. By means of a behavioural experiment on larval African catfish Clarias gariepinus in the laboratory, we determined colour vision and colour discrimination in dim light. Light-adapted larvae were subjected to classical conditioning to associate a reward feed with a green or a red stimulus placed among 7 shades of grey. The larvae learned this visual task after 70 and 90 trials. A different batch of larvae were trained to discriminate between green and red and then tested for the ability to discriminate between these colours, as the light intensity was reduced. The larvae learned this visual task after 110 trials in bright light and were able to discriminate colours, as light was dimmed until 0.01 lx, the minimal illuminance measurable in this study, and similar to starlight. The retinae of the larvae were found to be light adapted at 0.01 lx; thus indicating cone-based colour vision at this illuminance. For comparison, three human subjects were tested under similar conditions and showed a colour vision threshold at between 1.5 and 0.1 lx. For the larvae of C. gariepinus, the ability of colour discrimination in dim light is probably due to its retinal tapetum, which could increase the sensitivity of cones.

The supply of wild fry of coral reef fishes for aquaculture has resulted in the deterioration of their natural stock status, causing public concern. Through a series of studies on the establishment of artificial-fry production technologies for coral reef fishes, we found that ovary, testis, eggs and fry of coral reef fishes have high or intermediate levels of arachidonic acid (ArA), which is a relatively minor component in temperate and cold-water species. In gonadal polar lipids of selected coral reef, in particular demersal fishes (19 species), ArA, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) levels ranged from 6.0% to 19.4%, from 0.9% to 6.2%, and from 7.9% to 27.8%, respectively. It is notable that the major highly unsaturated fatty acids (HUFA) of polar lipids in all coral reef fish gonads are DHA and ArA (not EPA) in a ratio of about 2:1. This result allowed us to speculate that not only DHA but also ArA may be nutritionally much important for egg development and larval growth in coral reef fishes. Thus, feeding trials were conducted to investigate the effects of dietary ArA supplementation on reproductive performance of coral reef rabbitfish (Siganus guttatus) broodstock. The number of spawning and the number of hatched larvae tended to be better in broodstock fed diets with ArA than in those fed a diet without ArA. Next, larval rearing tests were conducted to investigate survival and growth in rabbitfish fry fed live rotifers which had been enriched with or without ArA. Fry fed the rotifers enriched with a combination of DHA Protein Selco (Inve Aquaculture, Baasrode, Belgium) + 5% ArA (VEVODAR CRUDE ARACHIDONIC OIL, DSM Food Specialties, Delft, the Netherlands) showed significantly the best survival (44.4 ± 4.5% for Day 17 fry), although growth was not different among treatments. The present study indicates that ArA is not a minor component in coral reef fishes, and that dietary ArA is very promising for the improvement of fry production technologies of the coral reef fishes.

A refined formulated feed for the grow-out culture of tropical abalone Haliotis asinina was evaluated to assess its suitability for a shorter culture period (<8 mo). Refinement procedures focused on the application of additional binder (sodium alginate), use of different feed forms (molo and noodle forms), and incorporation of Spirulina spp. as alternate protein source in partial replacement of other protein sources. Groups of 22 postlarval abalone with mean initial shell length (SL, 29 ± 0.01 mm) and weight (5.67 ± 0.06 g), harvested from the mollusc nursery of Southeast Asian Fisheries Development Center, Aquaculture Department in Tigbauan, Iloilo, were stocked each as replicate in five plastic trays measuring 31.7×43.5×9.0 cm. The trays were suspended in five 1×2×1-m concrete land-based tanks representing the five dietary treatments. Abalone were fed either the refined formulated diet,molo form(RF-M), refined formulated diet, noodle form(RF-N), unrefined formulated diet, noodle form(UF-N), unrefined formulated diet, molo form (UF-M), and seaweed (NF), as the reference diet. Formulated diets and natural food were given at 2%-3% and 10%-15% (wet weight) of the body weight, respectively, once daily at 1600 h for 180 days. Water quality measurements were maintained at desired levels. A flow-through filtered seawater systemwith continuous aeration was provided in each tank. A parametric one-way analysis of variance (ANOVA) and Tukey's post hoc test were used to test the differences in abalone SL, weight gain (WG), and specific growth rate (SGR) while nonparametric Kruskal-Wallis test was used for daily growth increase in SL (DGSL) and feed conversion ratio (FCR) among the various dietary treatments. Percent diet water stability and apparent digestibility coefficient for dry matter (ADMD) and apparent digestibility of seaweed as ingredient were, likewise assessed. A Hedonic scale taste test analysis was done to assess differences in abalone meat quality. Highest mean WG (239.17% ± 26.05%), mean SL increase (91.51% ± 3.28%), DGSL (2,296.67 µm/day), SGR (4.04 ± 0.27) were attained with abalone fed RF-N. Values, however, were not significantly different (P > 0.05) for all growth parameters in RF-M except for percent increase in SL at 74.25 ± 3.11. Abalone given UF-N and UF-M showed significantly lower mean WG and SL. Survival was high and was significantly different (P < 0.05) between treatments. The highest FCR was obtained with abalone fed seaweeds. Apparent digestibility for dry matter of both the RF and UF were high at 95.67% ± 1.17% and 95.95% ± 0.45%, respectively. Apparent digestibility of ingredient seaweed was 99.4% ± 1.38%. Regression analysis of data showed better percent water stability for RF (57%; R² = 0.954) compared with UF (38%; R² = 0.790) after 24 h. Meat quality of the final product assessed through Hedonic scale taste testing and one-way ANOVA did not show any significant variations in taste, texture, color, odor, and general acceptability. Results have demonstrated that the refinement done on the formulated feed may enable the abalone to grow to its marketable size of about 5-6 cm in a shorter culture period (180 days) in concrete land-based tanks.

Growth hormone regulates growth and development in vertebrates. As a first step to understand the role of growth hormone in the regulation of growth and development of the mangrove red snapper Lutjanus argentimaculatus, the red snapper growth hormone (sGH) cDNA was cloned using reverse transcription - polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends. The expression of sGH mRNA in embryos and larvae was examined also by RT-PCR. Excluding the poly-A tail, the full-length red snapper GH cDNA is 945 base pairs (bp) long. It contains untranslated regions of 99 bp and 234 bp in the 5’ and 3’ ends, respectively. It has an open reading frame of 612 bp coding for a signal peptide of 17 amino acids and a mature hormone of 187 amino acid residues. Red snapper GH contains 4 cysteine residues and the typical polyadenylation site 16 bp upstream of the poly-A tail. Based on the amino acid sequence of the mature hormone, sGH shows higher sequence identity (>75%) to GHs of perciforms like grouper, seabass, tilapia and rabbitfish than to GHs of salmonids and carps. Semi-quantitative RT-PCR showed that expression of sGH mRNA commenced two days after hatching.

In the retina of the African catfish Clarias gariepinus, the pigment epithelium and the tapetum were formed in newly hatched larvae, the cones developed within 2 days, and the rods within 3 days after hatching. The retinal tapetum shone under surface light under a light microscope; the shine was located in the apical projections of the pigment epithelial cells. Early appearance of the retinal elements enables African catfish larvae to see and feed well even in dim light.

Understanding the physiological condition of seaweeds as influenced by biotic and abiotic stress is vital from the perspective of massive expansion and sustainability of seaweed-based industries. The photosynthetic responses ofNeosiphonia sp. epiphyte-infected (INF) and healthy (HEA) Kappaphycus alvarezii under various combinations of irradiance, salinity and pH were studied using photosynthesis-irradiance (P-E) curves. Measurements of algal photosynthetic rates, expressed in terms of amount of oxygen production per fresh weight biomass per unit time (mg O₂ g⁻¹ FW h⁻¹), were carried out using the light-dark bottle technique. Neosiphonia-infected K. alvarezii (INF) had lower photosynthetic rates than healthy ones (HEA). Similarities (p > 0.05) in light-saturated photosynthesis rates (P_max) and significant differences (p < 0.05) in initial slope of curve (α) between INF and HEAK. alvarezii suggest that both samples are adapted to similar light conditions and differs only on photosynthetic efficiency. Low P_max (0.7–2.0 mg O₂ g⁻¹ FW h⁻¹) and high initial saturation irradiances (E_k = 90–519 μmol photons m⁻² s⁻¹) of INF seaweeds resulted to their low photosynthetic efficiency (α = 0.002–0.010). Such decline in α is attributed to the epiphyte, as Neosiphonia sp. covered almost the entire surface of K. alvarezii. An increase in chlorophyll-a (35–42.1 vs. 27.7–31.5 μg g⁻¹ FW, HEA) and phycobilin (1.96–2.39 vs. 1.16–1.58 mg g⁻¹ FW, HEA) contents was also observed in INF samples, suggesting acclimation to low-irradiance conditions, as a result of competition for light between the epiphyte and host. Both INF and HEA K. alvarezii also exhibited broad photosynthetic tolerance to short-term changes in irradiance, with no photoinhibition at the highest irradiance of 850 μmol photons m⁻² s⁻¹. K. alvarezii had a euryhaline photosynthetic response, with optimum salinity of 35 psu. Photosynthetic rates increased with decreasing pH, revealing K. alvarezii’s ability to modify its photosynthetic affinity for acidic seawater conditions; yet, their underlying mechanism of response to pH shifts still need to be further examined.

The effects of using thraustochytrid Schizochytrium sp. as source of lipid and fatty acids in a formulated diet on growth, survival, body composition, and salinity tolerance of juvenile donkey’s ear abalone, Haliotis asinina, were investigated. Treatments consisted of diets either containing a 1:1 ratio of cod liver oil (CLO) and soybean oil (SBO) (Diet 1) or thraustochytrid (Diet 2) as source of lipid and fatty acids at 2 % level. Natural diet Gracilariopsis heteroclada (Diet 3) served as the control. No significant difference in growth was observed in abalone fed Diet 3 (SGR: 5.3 % BW day⁻¹; DISL: 265 μm day⁻¹) and Diet 2 (SGR: 5.2 % BW day⁻¹; DISL: 255 μm day⁻¹). Survival ranged from 78 to 85 % for all treatments and was not significantly different from each other. A 96-h salinity stress test showed highest survival of 84 % in abalone fed Diet 2 compared with those fed diets 1 and 3 (42 %). The high growth rate of abalone fed Diet 2 and high tolerance to low salinity could be attributed to its high DHA content (8.9 %), which resulted to its high DHA/EPA ratio of 10.5 %. These fatty acids play a significant role in abalone nutrition. The fatty acid profile of abalone meat is a reflective of the fatty acid profile of the oil sources in the diet. The present study suggests that the use of Schizochytrium oil in lieu of CLO and SBO can support good growth of abalone which is comparable with abalone fed the natural seaweeds diet.