Climate change, temperature and tuna
It is widely appreciated that the ocean holds many phenomena that we do not know or understand, now, researchers have answered one question about the warm-blooded nature of some ocean dwellers.
Most fish are cold blooded, but some are warm blooded and this has hoodwinked marine biologists for some time as to the evolutionary advantage of this, especially as it seems to only occur in a few species.
An international research team led by Trinity College Dublin’s School of Natural Sciences (Ireland) has found a correlation between warm-blooded fish that can regulate their own body temperature and an ability to swim faster; as seen in white sharks and the endangered bluefin tuna. However, these species generally only live in waters with a narrow range of temperatures.
This revelation in habitat temperature, published in Functional Ecology, highlights that these species are just as likely to be affected by global warming and increasing ocean temperatures as cold-blooded species, for which this was already a concern.
Lucy Harding (Trinity College Dublin), the first author of the research article, stated:
“Scientists have long known that not all fish are cold blooded. Some have evolved the ability to warm parts of their bodies so that they can stay warmer than the water around them, but it has remained unclear what advantages this ability provided.
“Some believed being warm blooded allowed them to swim faster, as warmer muscles tend to be more powerful, while others believed it allowed them to live in a broader range of temperatures and therefore be more resilient to the effects of ocean warming as a result of climate change.”
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The research team collected data from wild sharks and bony fish, complimenting this data with that from publicly available databases. To do this, the researchers caught the fish and attached a waterproof biologging device to their fin, which could be used to remotely gather information on the temperature of the water where the fish swam, as well as the speed and depth at which the fish swam.
The results of the data analyses showed that warm-blooded fish were swimming 1.6 times faster than cold-blooded species, but they stuck to waters with a less diverse range of temperatures. This finding is the first piece of direct evidence showing that being warm-blooded is an evolutionary advantage for some species of fish.
Nick Payne, of Trinity College Dublin’s School of Natural Sciences and coauthor on the paper, commented on what these findings could mean for our understanding of the species and for future safeguarding efforts:
“The faster swimming speeds of the warm-blooded fishes likely gives them competitive advantages when it comes to things like predation and migration. With predation in mind, the hunting abilities of the white shark and bluefin tuna help paint a picture of why this ability might offer a competitive advantage.
“Additionally, and contrary to some previous studies and opinions, our work shows these animals do not live in broader temperature ranges, which implies that they may be equally at risk from the negative impacts of ocean warming. Findings like these – while interesting on their own – are very important as they can aid future conservation efforts for these threatened animals.”
