The thyroid hormone levels in female rabbitfish, Siganus guttatus, plasma, eggs, and yolk-sac larvae were measured before and after thyroxine (T₄) injection in female spawners at doses of 1, 10, and 100 μg T₄/g body weight (BW) fish. T₄ and triiodothyronine (T₃) levels in maternal plasma, eggs, and yolk-sac larvae were elevated following T₄ administration. Apparently, there is conversion of T₄ into T₃ in the broodfish which suggests the presence of the enzyme, 5′-monodeiodinase, in rabbitfish. T₄ and T₃ in maternal circulation were easily transferred into the oocytes and subsequently into the larvae. Larvae from spawners treated with 10 and 100 μg T₄/g BW tended to be longer and showed sornewhat better survival compared to the control and those injected with 1 μg T₄/g BW 7 days after hatching. These findings suggest that thyroid hormones may play an important role during early larval development of rabbitfish.

Egg cannibalism by milkfish spawners in a circular floating net cage was investigated. The cage was lined with a fine mesh hapa net to retain spawned eggs and to prevent the entry of fish egg predators. Water samples were collected from the surface (0 m), middle (1.5 m), and bottom (3.0 m) of a 10 m diameter by 3 m deep floating net cage at the time of initial detection of spawning (0 min) and at 30, 60, 120 and 240 min thereafter. The mean number of spawned eggs at the surface significantly decreased (P<0.05) 60 min after spawning and very few eggs were recovered 240 min later. There was no significant difference (P>0.05) in the mean number of spawned eggs collected from the middle and bottom of the net cage at various times after spawning. Eggs were found in the digestive tract of all milkfish sampled (n=6) at about 5 h after spawning, indicating that captive milkfish eat their own eggs. It is recommended that spontaneously spawned milkfish eggs should be collected immediately after spawning to avoid loss by egg cannibalism.

Three experiments were conducted to determine the effects of a simultaneous injection of varying doses of luteinizing hormone-releasing hormone analogue (LHRHa; 0.005–0.10 μg)/body weight (BW) in combination with a fixed dose of pimozide (PIM; 1 μg)/g BW on oocyte maturation and ovulation in the catfish Clarias macrocephalus (body weight: 39 to 167 g). This was done by monitoring the development and size of the oocytes after hormone injection at various sampling intervals for 48 hours. In Experiment I (March 1989), only the fish injected with 0.10 μg LHRHa + 1μg PIM/g BW underwent final maturation and ovulation. However, oocyte maturation and ovulation were observed in all treated fish in Experiment II (April 1989). Oocyte maturation and ovulation were also induced except in fish injected with the lower dose combination (0.005 μg LHRHa + 1 μg PIM/g BW) or PIM alone (1 μg/g BW) in Experiment III (September 1989). No maturation was observed in all vehicle-injected control fish in the three experiments. Mean egg diameter of fish that were induced to mature increased during ovulation but remained similar in size in fish which did not undergo final maturation. This study showed that captive C. macrocephalus can be induced to undergo oocyte maturation and ovulation at 15 to 16 h after a simultaneous injection of 0.01 to 0.10 μg LHRHa + 1 μg PIM/g BW.

The effect of cysteine concentration and cysteine source [cysteine, methionine or 2-oxo-thiazolidine-4-carboxylate (OTC)] on the metabolism of [35S]cysteine was studied in isolated rat hepatocytes. Production of each of the major metabolites of cysteine (glutathione, sulfate, taurine) increased as cysteine or methionine, but not OTC, concentration in the medium was increased. At equimolar exogenous substrate concentrations, cysteine availability to hepatocytes was greater from exogenous cysteine than from methionine, and that from methionine was greater than from OTC. The partitioning of cysteine, or the percentage of total metabolism resulting in production of each of the major metabolites, was markedly affected by cysteine concentration or availability. Low cysteine availability favored its utilization for glutathione; high cysteine availability favored its catabolism to sulfate and taurine. Under conditions of low cysteine availability (incubations with 0.2 mmol/L OTC), glutathione, sulfate and taurine production accounted for 90, 10 and 1%, respectively, of total metabolism. Under conditions of high cysteine availability (incubations with 1 mmol/L cysteine + bathocuproine disulfonate), glutathione, sulfate and taurine production accounted for 19, 47 and 34%, respectively, of total metabolism. Cysteine supplied as such and cysteine formed intracellularly from methionine were similarly partitioned. These studies demonstrate that methionine is not a superior substrate to cysteine for hepatic glutathione synthesis and that cysteine concentration (presumably intracellular cysteine concentration) has a major effect on the partitioning of cysteine sulfur to taurine in rat hepatocytes.

In the Philippines, small-scale fishermen have traditionally relied on informal lenders in view of the limitations of self-finance and the lack of access to bank credit. An assessment of credit practices and its availability in 5 coastal communities: Culasi, San Jose, Concepcion, San Dionisio, and Nueva Valencia, was conducted from February to August 1990. Ninety-six percent of the respondents surveyed considered fishing as their major source of income with average earnings from fishing of P1982/month (25 Philippines Pesos = US$1.). Hook and line, gill net, jigger, and spear are the common fishing gears used. Credit was obtained by 83% of the fishermen surveyed and was used mainly for food and household expenses, and fishing operations. Credit ranging from P20 to P20,000 was obtained from informal or non-institutional sources, such as relatives, friends, small store owners, and traders. Informal credit sources were preferred over formal or institutional sources for the following reasons: accessibility (51%), fast credit extension (31%), liberal terms (25%), and being only source known to the fisherman (18%). Analysis showed that income has a highly significant linear correlation with amount of credit (r2=0.1311). Income from fishing is not enough to cover the basic necessities of a small-scale fisherman's household, hence the dependence on informal credit.

The process of spermatogenesis and spermiogenesis in the river sculpin,Cottus hangiongensis, was observed ultrastructurally. During spermatogenesis, some germinal cysts in the seminal lobules were found to contain spermatocytes, which were provided with irregularly shaped nuclei, doughnut-shaped mitochondria, and atypical intercellular bridges with multiple disk-like cisternae. In addition, many cysts containing binuclear spermatids were observed in the testis. Within the condensed chromatin of the paired nuclei of the aberrant spermatids, highly electron-dense granules occurred, becoming the core of successively developing chromatin globules. The chromatin globules increased in size, resulting in an enlargement of the paired nuclei. These cells were finally released from the cyst into the lumen of the seminal lobules and underwent further degeneration, thus appearing as characteristic ‘spermatid masses’ in the mature testes.

The histological changes in the ovary and female-specific protein levels in the hemolymph during sexual maturation of Penaeus indicus were determined. Ovarian maturation was classified into four stages: immature stage, consisting mainly of oogonia and primary oocytes; maturing stage, composed of oocytes with yolky substances in the cytoplasm; mature stage, oocytes with club-shaped cortical rods in the peripheral cytoplasm; and spent stage, composed of primary oocytes, oocytes with yolky substances and scattered residual rod-like bodies. Female-specific protein levels in the hemolymph were low in the immature stage (4.45 µg/ml), increased significantly in the maturing stage (23.53 µg/ml), peaked in fully mature (48.30 mu g/ml) and decreased in spent (22.86 µg/ml) females.

Ozonation as a method of treatment for highly polluted slaughterhouse wastewater and slightly polluted laboratory wastewater was investigated. The results showed that use of a low concentration ozone stream (0·11 g h⁻¹) for removal of the majority of organics in slaughterhouse wastewater was not feasible, whereas application of the technique for less polluted chemical laboratory wastewater was feasible for ultimate disposal purposes.

Thirty new records of macrobenthic algae for Panay and Guimaras Islands are reported, consisting of 12 species of Chlorophyceae, 4 Phaeophyceae and 14 Rhodophyceae.

Vibrio sp., was consistently isolated from grouper, Epinephelus suillus, with bacterial infection. Fingerlings, which were challenged with the bacterium by injection, were highly susceptible. Immersion challenge resulted in 100% mortality within 48 hrs in fish subjected to combination of injury and exposure to the bacterium. Mortality in uninjured fish was observed in the long bath subgroup, but not in the short bath subgroup. These results are correlated with the present practices in the grouper fingerling industry in the Philippines.