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In April 1995. an unusual large-scale red tide of Heterosigma akashiwo (Hada) Hada occurred, causing massive fish kills in Kagoshima Bay. Japan. Four neurotoxic components, HaTx-i, HaTx-iia, HaTx-nb and HaTx-iii. which corresponded to brevetoxin components. PbTx-2. PbTx-9. PbTx-3 and oxidized PbTx-2, were inferred from analysis of Heterosigma red tide toxins on TLC and HPLC.

The ichthyotoxicity and toxin composition of a red-tide producing chloromonad Fibrocupsu juponicu (Toriumi and Takano) were examined. The flagellate showed the highest toxicity in mid-logarithmic phase and the lowest in the stationary phase with increased number of spherical-shaped cells. Five neurotoxic components, FjTx-I, FjTx-11, FjTx-IIIa, FjTx-IIIb and FjTx-IV, which corresponded to brevetoxin components, PbTx-1, PbTx-2, PbTx-9, PbTx-3 and oxidized PbTx-2 were tentatively identified from analysis of F. japonicu toxins on TLC and HPLC. The quantity of each component fluctuated with the age and growth stage of the culture. Among the five toxic components the yield of FjTx-I1 per cell was highest in both logarithmic and stationary phases.0

The project evaluated the effect of installing scrap bamboo (`kanchi') as a substrate for periphyton on growth and production of the indigenous major carp calbaush, Labeo calbasu (Hamilton). The impacts of ®sh grazing on the periphyton community were also assessed. Six ponds were used, three of which were provided with kanchi poles (700 per pond, spaced 30 cm apart). Ponds were limed and fertilized and stocked with L. calbasu ®ngerlings (mean total length = 5.16 cm; mean weight = 2.10 g) at a rate of 10 000 ®ngerlings ha ±1 (75 ®sh per pond). There were no statistically signi®cant differences in water quality between treatments, although differences in phytoplankton community composition were observed. Zooplankton numbers were the same in both treatments. While there was clear evidence that periphyton was being exploited by the ®sh, Chlorophycae being most affected, grazing was insuf®cient to cause signi®cant reductions in total periphyton densities. Fish survival and speci®c growth rates (SGRs) were signi®cantly higher in ponds with substrates, production in treatments with and without scrap bamboo substrate being 712.90 and 399.11 kg ha ±1 , respectively, over the 120-day period. However, production in both treatments was low in comparison with other studies, water temperatures (23.6± 32.7°C) being less than optimum for growth. It was concluded that kanchi and other locally available materials might be used to increase the production of some species of ®sh, although further evaluation of production economics is required. Periphyton-based culture of Labeo calbasu M A Wahab et al.Aquaculture Research, 1999, 30, 409±419 Periphyton-based culture of Labeo calbasu M A Wahab et al.

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