Who survives climate change? Fish guts could be a key factor

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Research from the University of Gothenburg has indicated that with rising temperatures, some fish will struggle to keep their digestion in order.

Albin Grans, study researcher behind the findings states that: "Our work is largely about trying to identify the physiological bottlenecks, in other words which parts of the body will fail first — whether the heart or the gut is the most sensitive part of the system." In the event, it turns out that the stomach is the twitchier of the two.

Fish are obviously ectothermic, relying on outside factors to govern their body temperatures — often erroneously referred to as 'cold blooded'. With rising temperatures of their environments, questions are raised about how well attuned their digestive functions are. After all, having developed to a pretty stable environment for millions of years, rapid change is something that ectothermic animals seem particularly badly adapted for.

Using Sturgeon, Trout and Sculpin, Albin trialled a range of temperature increases, recording changes in gut efficiency along the way. What was suggested by the results was that in more sedentaryfish (the Sculpins) it may be harder for blood flow to be maintained around the gut, making it harder to absorb nutrients from food.

In a nutshell, as temperature increases, so too does gut activity, in turn increasing a burden for energy to keep healthy.

However, for some species, a temperature increase may be quite welcome. Grans suspects that fish that currently live at lower extremes of temperature may benefit from a slightly higher temperature. As such, predictions between the impacts to different species will be difficult.

For aquarium owners, much of this will be old news, as many fishkeepers are well aware that keeping fish in too warm a temperature leads to emaciated bodies, hollow bellies, and eventual death. However, it was usually considered the case that it wasn’t possible to get enough energy into the fish, whereas the new findings suggest that blood flow around the gut is the issue, over quality or frequency of food.

For those interested in a little 'light reading' surrounding the subject, some more information can be found from the University of Gothenburg.

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