Osmoregulation and stress-induced responses in Atherinidae fish

• Grant number: 99/09755-5
• Support Opportunities: Scholarships abroad - Doctorate
• Start date: January 15, 2000
• End date: February 28, 2000
• Field of knowledge: Physical Sciences and Mathematics - Oceanography - Biological Oceanography
• Principal Investigator: Monica Yumi Tsuzuki
• Grantee: Monica Yumi Tsuzuki
• Supervisor: Fumio Takashima
• Host Institution: Pessoa Física
• Institution abroad: Tokyo University of Fisheries, Japan

Abstract

The pejerrey, Odontesthes bonariensis, a commercial valued Atherinidae species naturally found in South America, has been cultivated intensively for the past 20 years in Japan. However, its survival and growth rates under cultivation are still unsatisfactory possibly due to the lack of reliable techniques for larval rearing and grow out (including disease control, effective diets and knowledge on optimum environmental conditions). Pejerrey is generally considered as a freshwater species, mainly because of its natural occurrence in inland waters, and introductions have been made as such. However, preliminary evidence gathered in seed production centers and commercial farms in Japan suggests that mortality during situations of stress can be greatly minimized by the introduction of milIimolar amounts of salts to the water. Thus, it is possible that the variable and often low survival rates reported during seed-production or grow-out are due to the inadequacy of fresh water as a rearing medium for this species. Odontesthes hacheri, a dose relative to O. bonariensis but with a more temperate and seemingly freshwater natural distribution, was recently introduced into Japan based on assumption that is better adapted to life in fresh water. Nevertheless, information on the optimum salinity for this species is also not available. The aim of the present study was to understand the effects of salinity on viability, physiological matters and stress-induced responses during the ontogenetic development of O. bonariensis and O. hatcheri. Therefore, this study examined the effects of salinity on hatching, oxygen consumption, survival and growth of larvae and juveniles, and physiological adaptation to water salinity and stress-induced responses of juveniles and adults of O. bonariensis and O. hatcheri. Due to the interest in cultivation of O. bonariensis in fresh water and the possibility that adaptation to low salinity is strain-dependent, a limited study was also undertaken to compare the salinity responses of O. bonariensis eggs and larvae from different origins. (AU)