Overwinter Mortality of Fingerling Smallmouth Bass in Relation to Size, Relative Energy Stores, and Environmental Temperature

Hatchery-reared, 0+ age smallmouth bass (Micropterus dolomieui) of 55–107 mm total length were “wintered” from September 1975 to May 1976. Temperature regimes were modelled on those of the natural environment and final temperatures were 2, 4, and 6 C. Final wintering temperature did not noticeably influence mortality rates. Long fish survived the period of low temperature better than did shorter ones. Body ratios of dry weight/wet weight, lipid weight/dry weight, and ignitable weight/dry weight all decreased during wintering, and the data indicated that there may be critical percentages of dry weight/wet weight and ignitable weight/dry weight below which these fish will die.