Post
by Diana » Wed Feb 13, 2008 11:37 pm
In any rather shallow, somewhat open creek I would list birds and mammals as predators. Mammals have well developed senses of smell and taste, so if the prey tastes bad they might be deterred. (Chefkeith, how did that Loach-Licking test come out?) I am not sure about birds or reptiles. Would a bad taste slow them down, or teach them not to catch similar fish in the future?
Reptiles might be found in deeper water, or shallow, sun-lit or shade. I do not think that taste or smell plays much of a role in dictating to reptiles what to eat, either. (I might be all wet, here, it would not be the first time)
Predatory fish might be found in waters where there is more cover for them to hide, but not all predators hunt from ambush.
Of what benefit is a substance that can kill the fish that produced it?
Well, if it only killed under conditions that are not found in nature (Confined to a tank or bag, poor water flow, recirculated water of limited volume...) then the killing is a secondary or lower ranking effect, not likely to occur often enough in nature to become an evolutionary force. Hmm...
If, for some reason wild fish were confined to a small pool (Dry season...Small enough water volume that this toxin might kill) then what is the potential survival rate, anyway? Isn't such a pool drying up? Wouldn't so few fish survive that the death-by-drying vs death-by-own-toxin is not likely to be a factor. The fish is dead. That it could not tolerate the toxin that it produced in such a confined location is not important. It cannot reproduce. If it was more tolerant of the toxin, it would still be dead, and still cannot pass on tolerant genes.
The same species of fish, in a larger body of water that can produce a bad tasting toxin might be spat out by a predator, or might make the predator so sick that the predator leaves others of the species alone. The fact that the bad tasting toxin might have killed the fish in another setting is immaterial. The toxin has done its job of protecting the species. That predatory mammal will now be leery of spotted catfish, and will teach its young that spotted cats taste bad.
38 tanks, 2 ponds over 4000 liters of water to keep clean and fresh.
Happy fish keeping!