This study evaluated the feeding behavior of the milkfish (Chanos chanos Forsskål) in extensively managed brackishwater lagoons on South Tarawa, Kiribati (Central Pacific) in August 1998. Feed intake, dietary overlap, fish condition and morphometric intestine parameters were determined. The daily ration of fish was estimated using the ”modified Bajkov model”. Fish stomach content did not differ significantly between samples from day and night, but prey preferences showed significant differences (p < 0.05). Results were compared with a data set of juvenile milkfish from the Philippines raised under similar conditions.

The workshop was conducted to maintain linkage between Southeast Asian Fisheries Development Center, Aquaculture Department and its alumni. It also aimed to: assess the effectiveness of the training alumni and among trainees; inform alumni of the recent technologies developed by the Department; recommend ways to make the training courses more responsive to the needs of the fish farmers and the aquaculture industry. The training alumni identified several problems regarding the capability of the technical staff in aquaculture, i.e. shrimp seed production, marine fish seed production, grow-out culture, and fish diseases. The contributions of the selected participants during the meeting which are contained in this volume are cited individually.

The milt production responses of sexually mature sea bass Lates calcarifer to (D-Ala⁶, Pro⁹-N- ethylamide) luteinizing hormone-releasing hormone (LHRHa) and 17α-methyltestosterone injections were examined. At 24 h after injection of a low dose of LHRHa (20 μg/kg BW), the sperm count decreased significantly compared to saline-treated fish, but it returned to pre-treatment levels 48 h after injection, suggesting a possible hydration of the milt. Other milt parameters (milt volume, spermatocrit, sperm production) in LHRHa-treated fish did not vary from their controls at 24 or 48 h after injection but the overall pattern suggested a reduction in milt viscosity. Total expressible milt and spermatozoa collected over the 48-h experiment was approximately three-fold higher in LHRHa-injected fish than in saline-injected fish, indicating a stimulation of spermatozoa production, not merely milt dilution due to hydration. In a second experiment, sperm count and spermatocrit were significantly lower than those of saline-injected fish at 17 and 48 h after a single injection of a high dose of LHRHa (80 μg/kg BW). A methyltestosterone injection combined with the LHRHa injection also resulted in a significantly lower sperm count, but the spermatocrit remained comparable to the control group, suggesting a suppression of the LHRHa-induced milt hydration response. Results demonstrate that LHRHa stimulates milt hydration and spermatozoa production in milting sea bass and that a simultaneous methyltestosterone injection partially suppresses this response.

The occurrence pattern and population dynamics of Acartia tsuensis were investigated in a brackish-water pond in Panay Island in central Philippines by implementing both bi-monthly and daily sampling schemes. A. tsuensis occurred in the pond during the dry season (November-April) when the salinity of the water is in the range of 14 ~ 40 ppt but was completely absent at lower salinities. An almost constant rate of development from the nauplius 2 through to copepodite 5 stages of A. tsuensis was observed both in the pond and in the laboratory. The generation time ranged from 5.9~11.3 days. Fecundity had a positive linear corelation with chlorophyll a. Salinity and chlorophyll a affect the stage duration, mortality, and fecundity of A. tsuensis in the pond.

An illustrated account is presented, covering background (establishment of the department), plan of operation (functions; activities), project site development (Leganes Station, Tigbauan Station, construction of buildings, infrastructure development), research (prawn fry stocking, collection of prawn spawners, research staffing, research tie-up with Mindanao State University, Japanese fisheries experts), equipment (preparation of the list of Japanese donated equipment), organization of the department, funding.

The effects of alternate starvation and refeeding on food consumption and compensatory growth of hatchery-bred abalone, Haliotis asinina (Linnaeus), were determined. Two groups of abalone juveniles (mean shell length = 29 mm, body weight = 5 g) were alternately starved and refed a macro-alga, Gracilariopsis bailinae at equal duration (5/5 or 10/10) over 140 days. A control group (FR) was fed the seaweed ad libitum throughout a 200-day experimental period. Starved and refed abalone showed slower growth rates (DGR, 63 and 70 mg/day in the 5/5 and 10/10 groups respectively), as a result of reduced food intake (DFI 15% and 16% day⁻¹ respectively), after repeated starvation and refeeding cycles. Percentage weight gains (5/5 = 196%, 10/10 = 177%) were significantly lower than that of the control (397%). When refed continuously over 60 days, the starved groups exhibited increased DFI and fed at the rate of 24% and 25% day⁻¹, which were not significantly different from that of the control at 26% day⁻¹. At the end of the experiment, no significant differences were observed among three treatments in terms of shell length (range: 46–48 mm), body weight (range 25–28 g), % weight gain (392–465%) and per cent survival (range 87–98%). The results indicated that H. asinina had a complete compensatory growth following a return to full rations after a series of intermittent starvation and refeeding cycles.

In an attempt to understand growth regulation in milkfish, the milkfish growth hormone (GH) and its cDNA were characterized and the expression of GH mRNA in embryos and larvae was examined by RT-PCR. The milkfish GH was purified from an alkaline extract of the pituitary by reverse-phase high-performance liquid chromatography and detected as an immuno-positive protein with anti-salmon GH serum. The complete sequence of milkfish pre-GH was determined by cDNA cloning and nucleotide sequencing. On the basis of the N-terminal amino acid analysis of the native protein, the pre-GH was found to consist of a signal peptide of 22 amino acids and a mature protein of 188 amino acids. Milkfish GH shows higher amino acid sequence identity with GHs of carps (91–94%) and salmonids (70%) than with GHs of more advanced teleosts (<60%) in good accordance with its taxonomic position in teleosts. It has five half Cys residues, four of which are at positions homologous with those of other known GHs and the extra Cys with those of carp GHs. The molecular weight of milkfish GH was estimated to be 22 kDa, which is comparable to the theoretical value. This suggests that milkfish GH is a simple protein, although it has two potential N-glycosylation sites. Semiquantitative RT-PCR showed that GH mRNA expression was relatively weak in embryos and newly hatched larvae but was already strong in 2-day old and older larvae.

The effect of different dietary protein and lipid levels, and protein to energy (P/E) ratios on growth and body composition of the mud crab, Scylla serrata, was evaluated. Six practical test diets were formulated to contain three protein levels (32%, 40% and 48%) at two lipid levels (6% and 12%), each with P/E ratios ranging from 20.5 to 31.1 mg protein/kJ. Individual crabs were stocked in 36 units of 60-l tanks and maintained on a 40% protein diet until each molted (M₀). Newly molted crabs were weighed and fed the test diets until termination at 30 days from the third molt (M₃₊₃₀). Crabs were monitored daily and body weight (BW) taken after each molt, at intermolt and at termination. Average initial BW (11.18±0.66 g) was taken at 18 days after M₀. Carapace width (CW) at M₃₊₃₀ and of the exuviae (at molt 1, 2, and 3 or M₁, M₂ and M₃), weight of exuviae (M₁ to M₃), feed conversion ratio or FCR, duration of intermolt, and total number of days of feeding test diets (M₀ to M₃₊₃₀) were determined. At the end of the study, crabs were freeze-dried for analysis of nutrients in the flesh, exoskeleton and fat body. The FCR (3.21–4.21), intermolt duration and total number of days of feeding test diets (111.3–131.2 days) were not affected by dietary treatments (P>0.05). Analysis of covariance was used with CW at M₁ and BW at M₀₊₁₈ as covariates. CW in the 40% protein with 6% lipid or 40/6 diet (P/E ratio, 27.5 mg protein/kJ) did not increase when lipid was increased to 12% (40/12), and it was significantly wider than crabs fed the 48/6 and 48/12 diets (P/E ratios, 31.1 and 27.2 mg protein/kJ). CW and BW did not differ in the 40% and 32% protein diets and were not affected by dietary lipid level at every level of protein. Ca in the exoskeleton was lowest in the 32/6 diet, while exuviae weight was about one-fourth of BW. Crude fat in the lipid deposit of crabs fed 48% protein diets were low. Results showed that the mud crab, S. serrata, grow well when fed diets containing 32–40% dietary protein with either 6% or 12% lipid at dietary energy ranging from 14.7–17.6 MJ/kg.