The static biossays were performed to determine lethal concentration (LC50) values of four heavy metals (Cd++, Cr+++. Cu++. and Zn++) of spotted brown shrimp (Penaeus brasiliensis) The test animals were collected from the Laguna of Restinga, Nueva Esparto, and were acclimated in the laboratory condition for 11-21 days. Temperature and salinity were 22 ºC and 36 ppt, respectively. The LC50 values (mg/l) determined by probability-logarithm transformation were as follows-cadmium: 38 (24 -h), 21 (48 -h), and 12 (60 -h);chromium:40 (48 -h), 23 (60 -h), 13 (86 -h), and 10 (96 -h); copper: 24 (48 -h), 19 (60 -h), 16 (72 -h), 14 (86 -h), and 10 (144 -h); and zinc: 69 (24 -h), 25 (36 -h), 15 (48 -h) and 8 (60 -h). The LC50 values of 48 -h and 60 -h indicate that the most toxic heavy metals to P. brasiliensis in order are zinc, cadmium, copper, and chromium.

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.