Is there any data on which size trout survive better in the low water conditions: larger or smaller trout?
I don't have all the answers, but I'd imagine it depends on the method of death.
In many cases it's warm waters. Lower flows lead to warmer waters and less current adding oxygen to that water. Larger fish have higher oxygen requirements than do smaller fish, and hence are the first to go when waters get warm. That said, if there are a few select holding areas with cooler water remaining, thanks to say a spring or something, then the larger fish is also more able to dominate that spot.
On the other hand larger trout would better survive predation under low water conditions.
This is overly simplified.
Whether smaller fish or larger fish fare better is a function of the predator. Smaller fish get eaten more when the predator is larger fish or small birds or snakes. Larger fish get eaten more if the predator is large birds, raccoons, or fishermen.
If smaller trout survive better in low water or no water conditions might they be "selected" for survival thus explaining the lack of larger brook trout in streams that suffer low water conditions frequently?
I think streams that more often suffer from low water conditions frequently have smaller trout for other reasons. They tend to be smaller streams for starters.
I'm sure members will have opinions one way or the other.
I think every situation is different and it's tough to make sweeping generalizations. But if you were to ask me what is most common. Then I'd say that low water years lead to a decrease in both the number of fish as well as the average size of fish that are present. i.e. the big ones for any given stream fare worse.
