Development of salinity stress tests for larval striped bass, Morone saxatilis and inland Silver sides, Menidia beryllina, used in nutritional studies

Abstract

Salinity "stress tests" have previously been developed to detect subtle differences in physiological condition of larval fish between treatment groups in nutritional studies, when no differences exist in survival and growth. Methods that have been described in literature for Asian species include a) netting the fish out of water for a few seconds and measuring recovery time after its re-immersion and b) subjecting larvae to salinity stress for 2 h and measuring differences in mortality. In this study, we attempted to define the conditions for 15-h salinity stress tests with larval striped bass and 2-h salinity stress tests with inland Silver sides where a sharp delineation exists between survival and mortality and finally to use this test in a study of fatty acid requirements of the Silver sides. Striped bass larvae were cultured in an aquarium containing 5%0 water and fed on Reference Artemia nauplii for two weeks. Silverside larvae were reared in 30%o sea water and fed on fatty acid enriched or un-enriched Great Salt Lake Artemia nauplii for three weeks. Striped bass were then exposed to 10, 20, 30 and 40 %o salinities while inland Silver sides to 40, 60, 65, 70, 75, 80 and 100%o salinities and their survival was determined at 1/2 h intervals. Striped bass exhibited maximum survival at 20%o and below. About 15% died in 30%o water while all were dead in 40%o at the end of 2-h period. Mortality count was increased when exposure time was prolonged. Fish larvae displayed significant (p<0.05) differences in mortality when duration between feeding and their exposure to stress was increased. Silverside larvae displayed maximum survival at 60%o salinity and below but those raised on fatty acid enriched nauplii performed significantly (p<0.05) better than the controls in various stress tests. © Asian Network for scientific Information, 2010.