Thermal Shock Resistance of Spot (Leiostomus xanthurus) after Acclimation to Constant or Cycling Temperature

Postlarval and juvenile spots were acclimated to selected constant temperatures and to diel temperature cycles. Following acclimation they were exposed to temperature shocks from 0 C (control) to 20 C above acclimation temperatures. Twenty-four-hour median lethal shock temperatures (LS50 values) were calculated by probit analysis. The temperature cycles used had no apparent effect on the thermal shock resistance of either postlarval or juvenile spots relative to constant-temperature acclimation. When acclimated at the same temperatures, postlarvae had lower thermal shock resistances than juveniles. Most mortality occurred within 10 minutes of shock onset.