OVERWINTER MORTALITY OF YOUNG-OF-THE-YEAR STRIPED BASS (Morone saxatilis) IN FRESHWATER PONDS IN NOVA SCOTIA

Abstract

Commercial fishing for striped bass (Morone saxatilis) is very limited in Canada, therefore there is potential for pond-based aquaculture to fill the consumer market. One impediment to culture is high overwinter mortality among young-of-the-year (YOY) striped bass. In a culture setting, mortality is restricted to YOY bass transferred to cages in constructed freshwater ponds in November; larger bass (>500 g) typically survive well under the ice. Two trials were completed in consecutive winters (2016-2018) to investigate the effect of body size (range ca. 30-50 g), pre-winter diet, and pond characteristics on overwinter survival in 1m3 cages. Mortality rates varied between ponds and years from 10 to 100 % and was inversely related to body size in some cases but not others. Diet had an insignificant effect on survival. Muscle total lipid and triacylglycerol (TAG) and liver TAG proportions on a wet-weight basis were significantly higher when samples from November and March were compared. Phosphoethanolamine (PE) mass in total muscle phospholipid was higher in striped bass sampled in the winter, but proportions of 18:0 and 22:6n-3 in PE and 18:1n-9 and 22:6n-3 in phosphatidylcholine were lower in March samples. Striped bass appear to rely on other lipid classes or body tissues than those analyzed in this study to survive the winter.