The critical thermal maximum (CTM) and the first equilibrium loss (FEL) of six tropical marine fishes were determined. CTM were Mugil curema (41.4º C), Genres sp. (39.2ºC), Orthopristis ruber (38.7ºC), Archosargus rhomboidalis (39.39ºC), Gobioides sp. (38.6ºC).and Chilomycterus sp (39.3ºC). FEL's were Mugil curema (40.7ºC), Gerres sp. (38.5ºC), Orthopristis ruber (37.2ºC), Gobioides sp. (36.0ºC), and Chilomycterus sp. (38.3ºC). The mean difference between CTM and FEL ranged from 0.93 to 2.66ºC and was significantly different.
