The Israeli Journal of Aquaculture - Bamidgeh 54(2), 2002
The Annual Dan Popper Symposium


THE EFFECT OF REARING TEMPERATURE ON SEX DETERMINATION
OF EUROPEAN SEA BASS (DICENTRARCHUS LABRAX )
AT DIFFERENT REARING STAGES


Ishasar Ben-Atia*, Keren Bresler, Mirit Gada, Hillel Gordin, Sergei Gorshkov, Galina Gorshkova, Gilad Heinisch, William Koven, Sigal Lutzky, Iris Meiri, Adi Paduel, Benny Ron, Hanna Rosenfeld, Amos Tandler

Israel Oceanographic and Limnological Research, The National Center for Mariculture, P.O. Box 1212, Eilat 88112, Israel

Abstract

Sex differentiation in fish is controlled by genes but it has recently become apparent that sexual development in teleosts has some degree of plasticity and can be influenced by environmental factors. The main environmental factor influencing sex in fish is temperature. Somatic growth in male sea bass is lower than in females, resulting in an 18-40% smaller body weight at two years of age for males. In many Mediterranean and European cultured sea bass stocks there is an undesirably high proportion of males. Therefore, efforts are being made to change the sex ratio in cultured sea bass to favor females.

The objective of this work was to study the effect of different temperature regimes during the first 100 days after hatching on sex differentiation in European sea bass and to identify when plasticity of gonadal sex differentiation occurs. As there are indications that the genetic makeup of the population may influence its response to temperature, we examined the influence of temperature on sex determination in two Mediterranean strains of European sea bass. The results for both strains demonstrate that exposure to a high temperature (21C) during early development has a strong masculinizing effect. Conversely, exposure to a low temperature (13C) results in a population with a significantly higher percentage of females. The present study indicated that sex differentiation is temperature-sensitive from 10 to 90 days after hatching.

We showed that androgenesis can be prevented in European sea bass by exposing them to low temperatures during the larvae and nursery stages. Our results suggest that the low temperature treatment may not have long-term negative effects on growth rates and, to the contrary, such effects may be beneficial.

*Corresponding author. E-mail: sbenatia@ocean.org.il

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