Tieshangang Bay in the Beibu Gulf, Guangxi of China, is a strategic location for pearl farming. Although water pollution has been reported in this bay but the general health of the pearl oyster, Pinctada fucata martensii, farmed there has never been assessed. The present study examined the condition of P. fucata martensii farmed in the Tieshangang Bay by analyzing its length-weight relationship (LWR) and relative condition factor (RCF). A total of 111 specimens were sampled for measuring their shell height and total weight for determining the LWR and RCF. The coefficient of correlation of the LWR was high (R2 = 0.93), significant at 0.01 level. Negative allometric growth (b = 2.7048) was observed. However, P. fucata martensii achieved the expected growth in terms of weight, as determined through the RCF (mean 1.13). Negative allometric growth is commonly reported on the wild Pinctada spp. collected from different regions. Apparently, the water pollution in the Tieshangang Bay did not compromise the general health of the pearl oyster cultured there. Nevertheless, further study on the farm’s surrounding water quality and plankton availability is necessary to investigate the interaction between the growth of the oyster and its culture environment. In conclusion, the P. fucata martensii farmed in the Tieshangang Bay was considered healthy and the bay is still suitable for pearl oyster farming.

Knowledge on the visual spectral sensitivity of a given fish is important for determination of optimal light conditions for improvement of fish rearing in aquaculture.Sutchi catfish (Pangasianodon hypophthalmus Sauvage 1878) is an important freshwater fish species in Southeast Asia. The present study aimed to understand the visual spectral sensitivity of juvenile sutchi catfish through spectrophotometric measurement of the spectral absorbance of wholemounts of retinae. The spectral absorbance curves obtained from the spectrophotometric measurement indicated a parabolic shape. The curves for retinae photo-bleached with initial flash of blue, green and yellow lights, respectively had a peak at approximately 560 nm, which were the same as the curve for retinae photo-bleached with broad wavelength light. On the other hand, the curve for retinae photo-bleached with initial flash of red light had a peak shifted prominently toward shorter light wavelength at approximately 540 nm. This prominent shift of peak implied that the retinae of juvenile sutchi catfish absorb light wavelength of red. Therefore, the present results clearly suggested that juvenile sutchi catfish utilises longer light wavelengths.