Influence of salinity on morphological deformities in cultured larvae of Japanese eel, Anguilla japonica, at completion of yolk resorption

Abstract

The occurrence of morphological deformities under different incubation salinities (24, 30, 33, 36 and 42 practical salinity units [psu]) was examined in Japanese eel larvae. Fertilized eggs hatched at all salinity treatments. The survival rate until yolk resorption decreased at higher than 36 psu. The proportions of deformed larvae reared at 36 psu were significantly lower than at other treatments. Pericardial edema and abnormal lower jaw increased at lower than 33 psu and spinal curvature occurred at high salinity (42 psu). In contrast, the incubation salinity did not significantly affect the relative frequency of abnormal neurocranium. These results imply that the optimal salinities for rearing Japanese eel eggs and embryos are 34–35 psu from the viewpoints of survival and deformity. Taken together with previous study [Kurokawa, T., Okamoto, T., Gen, K., Uji, S., Murashita, K., Unuma, T., Nomura, K., Matsubara, H., Kim, H.S., Ohta, H., Tanaka, H., in press. Influence of Water Temperature on Morphological Deformities in Cultured Larvae of Japanese Eel, Anguilla japonica, at Completion of Yolk Resorption. J. World Aqua. Soc.], the rearing of eel eggs and embryos at 25 °C and 34–35 psu probably decreases the mortality and deformity rate of eel larvae at yolk resorption stage.