🌡️
Metabolism
Ectothermy
The energy strategy of fish and most non-mammalian vertebrates - body temperature tracks the environment rather than being metabolically maintained.
System: Endocrine Level: Beginner Discipline: Physiology
📖 Overview
Fish are ectothermic - they do not generate significant metabolic heat. This has huge consequences: metabolic rate roughly doubles with every 10 degrees C increase in water temperature, so a warm-water bass eats much more than a cold-water trout even at similar size. Fish activity, growth rate, and reproductive timing are all thermally driven. Some fish (tuna, some sharks) have regional endothermy - maintaining warmer muscle temperatures via countercurrent heat exchange.
🔑 Key Concepts
Q10 effect, metabolic rate, thermal niche, regional endothermy, thermal acclimation.
🐟 Examples
Bluefin tuna maintain deep-muscle temperatures 10-15 C above ambient via a rete-based heat exchanger - enabling continent-spanning pursuits in cold seas.
✨ Fun Fact
The opah (moonfish) - the only fully warm-blooded fish - keeps its entire body above ambient by using a countercurrent system in its gills, sparing heat that would otherwise be lost to the water.