Low-temperature tolerance of southern flounder Paralichthys lethostigma: Effect of salinity

Two studies were conducted to examine the influence of salinity on low-temp erature tolerance of southern flounder Paralichthys lethostigma. Juveniles (3.4 g +/- 1.2 g in study one; 32.8 g +/- 34.8 g in study two) were acclima ted to 20 C at salinities of 1, 5, 10, 20 and 30 parts per thousand in stud y one and 1, 10 and 30 parts per thousand in study two. Temperature was the n decreased approximately 1 C per day to a nominal 4 C and 2 C, in studies one and two, respectively. Fish were subjected to the low temperatures for 10 d and then returned to the initial temperature (20 C) at a rate of appro ximately 1 C per day. Mortality ranged from 0 to 10% in study one and from 30 to 100% in study two and was significantly affected by salinity. Results of this re search suggest that the chronic low-level tolerance limit is be tween 2 and 4 C and that increased salinity offers some mitigating effect.