Eggs of Atlantic silverside, Menidia menidia, were fertilized and incubated at 15, 17, 20, 25 and 30 C. The times to hatching at each temperature were 27.0, 12.4, 9.8, 4.8 and 3.0 days respectively. Thermal shocks of +8 C produced 0% mortality for larvae reared at 17 and 20 C, 19% for larvae reared at 25 C, and 11% for larvae reared at 30 C. Thermal shocks of q-•[4 C produced 3% mortality for larvae reared at 17 C, 0% for larvae reared at 20 C, and 100% for larvae reared at 25 and 30 C. Since the larvae of Menidia menidia are present in Long Island Sound when temperatures are in the 15-20 C range, it appears that the population will undergo a minimum of stress due to thermal shock as a result of nuclear power plant development on Long Island.