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Luc I expect you are right. As much as we would prefer they were not there if the one I have is anything to go by the savage bugger should be easy to catch and put up a good fight.
i think the temps they can handle are about down to 9 degrees. word is that many of them die back in winter, ive read of fish kills for cichlid species. its about 11 degrees to 8 degrees depending on species. Ive heard stories of mangrove jacks and togas dying off in particularly cold winters too, in the upper creeks anyway.. i guess its a matter of waiting for after the next coldest period and see. if the water is deep then they have some buffer against the cold. it could be they might die off in the shallow rivers just to start up again from the dams after the next big overflow.
Unfortunately, given natural selection, those that survive the cold temperature will pass it on to their offsprings and so on.
Eventually, you'll have a strain of chiclids that will tolerate quite low temperature.
The same happened to tilapia in NPD. Cold snaps used to result in large kills of large adults. Over the years they have been in there, those able to survive at lower temps have passed this on.
The incidence of winter fish kills of large tilapias is not as great as it once was.
I think the victorian government were going to spend a million or are doing so to try stop cichlid species in vic, you are probably right on the money for them getting resistance to the cold in qld, i was unaware of how many years theyve been caught there for and unaware of there being no recent fish kills..but we have had some of the hottest years in the last decade which wouldnt help. natural selection will only go so far by the looks of tilapia mappings across the world.
in places where fish kills occur, sometimes it because of a nutrient load and then a series of cloudy days not allowing for oxygen to go into the water fast enough to support the biomass so its a ussual occurance for a population to reach a big mass and die back some and the big fish run out of oxygen first.
but i do think thats a bit far fetched that they will take in vic, unless its a strain i am not aware of or unless they are talking trying to wipe out the population at the cooling dams of Hazelwwood power station. thats 26C all year round and they do not survive in the waters leading out of the area in winter and they have been there over 20 years now. but 26 to 5 degrees temp change is a lot different to what happens in qld.
what we can see is that tilapia are all around florida USA but do not survive or have not established in far north americas. america is a place that grows tonnes and tonnes of them all over the country and in recirculation indoors systems and hothouses etc outside their establishment range.. i recall there being a population in the tweed many years back, more of an aquarium type smaller strain i thought. i think it started as far west as north of kyogle but i forget the town now. NSW fisheries has always said there is no wild pops in NSW, except for a blue hole at yamba which holds warmth from running so deep into the ground..but the top of nsw could be a location they could get into and by the sounds of some posts on here, they already are.
people were surprised that the floods in the 70s didnt spread cichlids everywhere around brisbane, and they were sure in the country and the area back then in peoples home aquarium tanks atleast but by now, you would imagine that there would be a lot that got ditched from tanks as the houses went under recently but also in the last few decades from kids, young adults and irresponsible adults releasing them. so we can have floods that might wash a lot away but then the dams are still a future source. fisheries is going to tighten up on the keeping of them as pets no doubt, but i reckon its far too late now. i think a big part of the problem is because they breed readily, there are a lot of species that hobbyists will get into to make a buck, then once everyone is making a buck the price drops. so they move onto another type that has value still. then if they have too many, they think, ill let it go in the local header dam. thats illegal and so are a lot of them in the country, but there is a black market and so where there is black market money you get laws broken. ive seen a few times people mention on fish keeping forums that colourful strains have been found in dams and i imagine a lot of cichlid species can hybridise cause they are still closely related. so when the flood over, who knows what the variety has in its bloodlines!
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