Temperature effect on the metabolism of fish?

[Zoodiver]

So they would act like over wintering Koi and eventually starve at that temp?

Yes. Several things happen in colder temps. Blood density and blood oxygen levels change. That directly relates to organ function. Things slow down and will shut down 100% at a certain point (different for each species and even variable by fish sometimes). I have seen fish in water far colder than I thought possible, but it doesn't come without side effects. Fish kept outside their natural temp range will suffer developmental issues that will lead to a shorter lifespan.

A great example happend a few years ago in FL. Marine fish (and coral) here see water temps dip into the low 60F upper 50F in the Winter. It clearly slows down feeding and activity levels. A few years ago it hit low 50F and some of the coldest nights there were pockets that hit upper 40F. Die off was HUGE. There are areas that are still trying to recover a few years later. That line in the low 50s was the breaking point for many animals. Those same animals see mid 90F in the Summer. So even thought the change is slow, they can still reach a breaking point.

 

[MyGiants]

Slow gradual drop for tropical like from 80F+ to 60F maybe even 50F depends on the fish. Some will start to get very lethargic there metabolism will slow to a point where they are barely moving. Some may even get sick before that. Depends on the fish. I saw a documentary where they tested how low they could gradually lower the temp on Piranhas. I think they were able to get the temp down in the low 50F before the drifted off to sleep never to awake!

 

[jprp]

It puzzels me why a species such as clarius should be so invasive, i know they have breathing advantages over many other fish but they seem to have a tolerance for temperatures a bit different to that encountered in their natural range.
US residents what are the lowest temps in states that they have become a problem?

 

[blindkiller85]

It puzzels me why a species such as clarius should be so invasive, i know they have breathing advantages over many other fish but they seem to have a tolerance for temperatures a bit different to that encountered in their natural range.
US residents what are the lowest temps in states that they have become a problem?

Google might help you with that, first on the result list was Indiana.

Snakeheads are much more of a problem and still a tropical fish that is extremely hardy. Being found in pretty much the eastern half of the country. Michigan, florida, Indiana, Illinois, Missouri, a mass majority of the mississippi river if I'm not mistaken.