Environmental temperature and body
temperature in fish
Fish, amphibians and
reptiles belong to a group called ectotherms meaning that these
animals do not produce heat to maintaining a constant and normally
high body temperature (as is the case for birds and mammals). Instead
they rely on the environment and their own behaviour to control their
temperature. For fish, this means that body temperature varies
directly with water temperature as seen in the diagram below.
Ectotherms can be
into poikilotherms and homoetherms. In the
poikilotherm group, the body temperature varies over time with
environmental temperature. In the homeotherms, the environmental
temperature is stable which means that the body temperature is also
stable. In fish, most species are poikiolothermic ectotherms, but
Antarctic and deep sea living species are homeothermic ectotherms.