# Opah is the only fully warm-blooded fish Some fish can keep part of their body warm, like [[Bluefin tuna's body stays warm but its heart does not|bluefin tunas]], but opah can keep their entire body between 13°C and 14°C. Scientists did not find out about this until 2015. We really don't know much about deep sea creatures. --- Source: [Science](https://www.science.org/content/article/scientists-discover-first-warm-bodied-fish)