Experiments were conducted to determine the effects of poor nutrition on the growth of three Oreochromis niloticus strains fed protein-deficient diets. Four-week-old fry from the three "test" strains were paired with a fourth "reference" strain of tilapia (red) of the same size and stocked in 60-1 aquaria. The treatment lasted 6 weeks, with fish being fed commercial fish feed crumbles for the first and last 2-week periods and rice bran during weeks 3 and 4. Control fish were fed commercial diet throughout. Both control and treatment fish were fed at 20% of fish biomass per day. Lengths and weights were measured every 2 weeks. Significant strain effects were noted when the growth of test fish over the whole experimental period was analysed by analysis of covariance using the reference fish growth as a concomitant variable. The relative growth of the three test strains differed at each feeding phase. The NIFI strain grew best during the commercial feed phases, the Israel strain performed best during the rice bran phase while the CLSU strain, regardless of the type of nutritional environment, usually ranked last. Different performance rankings at each feeding phase represent strong genotype X environment interaction among these commercially important lines. This was statistically confirmed by analysis of covariance of the growth of the Israel and NIFI strains during the different feeding phases using the reference strain as a covariate.

Annual changes in testicular activity and concentration of two serum androgens were monitored in two groups of the river-sculpin Cottus hangiongensis collected from the upper and lower reaches of a river at southern Hokkaido, Japan. One of them (early maturing group) underwent testicular maturation with aberrant spermatids and spermatid masses produced during the reproductive cycle. Moreover, regular seasonal changes in serum testosterone and 11-ketotestosterone concentrations were observed. On the other hand, in the other group (delayed maturing group), although body size of the fish was large enough to undergo reproduction, annual changes in gonadosomatic index and testicular activity did not vary much. During the months of active testicular development in the early maturing group, spermatogenesis was observed to begin in some regions of the testes of delayed maturing fish, but always resulted in the formation of aberrant spermatids and spermatid masses. Moreover, concentration of serum androgens did not significantly vary throughout the year. Results suggest that low androgen production is a proximal factor for delayed sexual maturity in the delayed maturing group, and that the occurrence of aberrant spermatids and spermatid masses during spermatogenesis is not linked to the delayed maturity.

Soaking fresh ipil-ipil, Leucaena leucocephala, leaves in tap water (1:1, v/v; or 50 g in 500 ml) for 30-48 hours with a water change after 24 hours extract atleast 90% of its mimosine, a toxic lysine derivative. This extraction procedure is more economical and practical for fish farmers than the use of dry or moist heat or iron compounds. Soaked or unsoaked leaves of Peruvian or Hawaiian ipil-ipil Leucaena leucocephala formed 1/3 of trial diets fed to Penaeus monodon juveniles (1-2 g). Other protein sources consisted of fish and shrimp-head meals. A diet without ipil-ipil leaves (FS) served as the control. After 8 weeks, the mass weight of shrimp fed the FS and soaked Hawaiian leaf diets (HLS) was significantly (α= 0.05) higher than soaked (PLS) and unsoaked (PLU) Peruvian leaves. The HLS group had a significantly higher survival rate than the PLS and PLU groups but not the FS-fed shrimps; survival among shrimp fed unsoaked Hawaiian leaves (HLU) was zero. It was found that the Hawaiian variety of ipil-ipil leaves when soaked for 24 hours can be incorporated in the P. monodon juvenile diet with good survival (87%) under laboratory conditions. However, the optimum amount of leaves to be included in a low cost and efficient diet has yet to be determined.

Steroid hormone profiles accompanying sexual maturation in captive milkfish are described. There were no significant differences in levels of serum estradiol 17-β (E₂) and testosterone (T) between immature male and female fish. Mean E₂ levels rose from 0.54±0.11 ng/ml in immature females (Stage 1) to 4.53±1.16 ng/ml in vitellogenic females (Stage 5), while T levels increased from 2.06±0.28 ng/ml to 38.4±9.26 ng/ml. E2 and T levels were positively correlated to GSI and oocyte diameter. In males, serum T levels increased from 2.5±0.40 ng/ml in immature males to 27.73±5.02 ng/ml in spermiating males. A significantly higher T level was found in males with thick and scantly milt (spermiation index, SPI, 2) compared to males with scanty milt (SPI, 1) or males with copious, fluid milt (SPI, 3). Serum levels of E₂ and T, and the GSI in females rose significantly during the breeding season (April–June 1983). The levels of both steroids dropped below 1 ng/ml in spent females sampled in succeeding months. In immature males, T levels ranged from 1.11 ng/ml to 2.78 ng/ml and rose significantly to 21.52±8.38 ng/ml during the breeding season when GSI peaked. Serum T levels dropped to around 10 ng/ml in the succeeding months when only spent or regressed males were sampled.

Seasonality of yield and gel strength of agar from Gracilaria heteroclada was determined. Gel strength was high (510-794 gm cm^-2) during early dry season (October-March) and low (43-101 gm cm^-2) during the wet season (May-August). A negative correlation exist (P ≤ 0.05) between agar yield and gel-strength.

A condition of the tetrasporophyte stage Gracilaria spp., characterized by white to pinkish discoloration and gradual disintegration of the thallus, has been observed in tank-held stocks. Microscopic observation revealed no fungal or protozoan parasites. Appropriate dilutions of homogenates plated on nutrient agar and bromthymol blue teepol agar showed the presence of bacteria, all of which were agar-digesting, at the rate of 1.42 × 10⁷ cells per g of affected thalli. Colonies on bromthymol blue teepol agar were round and yellow, while those on nutrient agar appeared creamy and round with entire edges, and were rapid agar digesters. The bacteria were Gram negative, fermentative and motile rods. Based on biochemical characteristics, the isolates were classified as belonging to the genus Vibrio. Microscopic observations of thalli cross-sections showed erosion of the pericarp, thus revealing the cortical and the medullary cells. Scanning electron microscopy revealed rod-shaped bacteria, including dividing cells, in affected tissues. Antibiotic sensitivity tests indicated that the bacteria were sensitive to Polymyxin B, nalidixic acid, nitrofurazone and oxytetracycline.

A survey was conducted in 12 coastal municipalities of Western Visayas, Philippines from March to July 1990 to determine the seaweed gathering practices of fishermen. There were 83 gatherers involved in this small-scale industry, who live below the poverty line and who consider it as the number one minor source of income. Only seaweeds of commercial value are gathered in big volume. There were approximately 114 T year^-1 of seaweeds harvested from natural stock with a market value of P414, 950.00 ($14,819.64). The harvest is broken down into 3 main groups: (1) agarophytes, 99.5 T (Gelidiella, Gracilaria and Gracilariopsis), (2) carrageenophytes, 10 T (Eucheuma and Kappaphycus) and (3) table vegetable, 10 T (Caulerpa). An average maximum income of P5,600.00 or $200 gatherer^-1 season^-1 is derived from seaweed gathering.

The influence of extraction time on the clean anhydrous yield, rheological properties, dynamic gelling and melting temperatures of 1.5% agar from six species of Gracilaria and one species of Gracilariopsis collected from the Philippines was determined. The lowest agar yield was measured from Gracilaria 'verrucosa' (10.1%) even after 120 minutes extraction while the highest yields were recorded from G. coronopifolia both after 30 (23.5%) and 60-minute extraction times (26.1%) and G. eucheumoides after 120-minute extraction time (27.3%). A 60-minute extraction of G. heteroclada produced gels with the highest breaking strength (1013 g), the maximum cohesiveness (7.4 mm), the greatest breaking energy (7481 g mm), and the greatest stiffness (137.3 g/mm ^-1). Gracilaria blodgettii gave the weakest gel tested. Dynamic gelling temperature was lowest for G. blodgettii at 60 min (28 °C) and highest for G. edulis at 120 minutes of extraction (46.3 °C). Melting temperature was lowest at 30 min extraction for G. salicornia (58.0 °C) and highest at 30 minutes for G. edulis (95.0 °C). A strong interactive effect of species, extraction time, and rheological properties was observed, but there was no interaction observed among the species, extraction time and temperatures. Each species showed good rheological properties at a specific extraction time.

The effect of light color (green, blue and white fluorescent lights, with natural light as a control) on maturation in intact and eyestalk-ablated Penaeus monodon was tested in 12-m³ broodstock tanks. Size and quality of sequential spawns from ablated females were also compared. In Experiment 1, unablated females under green light produced the highest number of spawns (5), total number of eggs (4.26 × 10⁶), total number of nauplii (2.69 × 10⁶) and mean egg counts (6537 eggs g⁻¹ female), the latter significantly higher than in the other treatments. Mean nauplii counts were higher under green (3979 g⁻¹ female) and natural (3303 g⁻¹ female) light compared to the other treatments. Mean hatch rate was highest in control (87.3%) but this was not significantly different from green light (61.8%). In Experiment 3, ablated females under natural light gave the highest total number of eggs (13.04 × 10⁶) and nauplii (9.74 × 10⁶). Mean egg and nauplii counts were significantly higher in the natural (4436 eggs and 3308 nauplii g⁻¹ female) and green (4016 eggs and 2906 nauplii g⁻¹ female) light treatments compared to white. Hatchability was similar for all treatments. In Experiment 2 (using green light), ablation increased the total number of spawns, eggs and nauplii 14 to 17 times. Rematuration data showed no significant differences in spawn size (egg counts); hatchability and nauplii counts of sequential spawns were similar in Experiment 2 but tended to decrease in Experiment 3.

Specific growth rates (% day^-1) and production rates (g m^-2 day^-1) of Gracilaria sp. reared in net cages on a bamboo floating raft from March 1989 to February 1990 were determined at different stocking densities (200, 250, 300 and 350 g 0.5 m^-2/net cage). Mean specific growth rates for the whole culture period were highest at stocking densities of 200 and 250 g 0.5 m^-2 (P < 0.05). Highest mean net production rate was obtained at a stocking of 250 g 0.5 m^-2, but was not significantly different from stocking densities of 300 and 350 g 0.5 m² (P < 0.05). Highest monthly mean specific growth rates and monthly mean net production rates for all treatments were obtained during March and November 1989 and February 1990. There were no significant differences (P > 0.05) in monthly mean specific growth rates and mean net production rates between the three peak months, although they were significantly different from the rest of the months (P < 0.05). Production was higher during the dry season. Correlation analysis showed that total rainfall was negatively correlated with specific growth rate and production rate. Salinity, temperature and pH were not correlated with specific growth rate and production rate.