Thread: Fish Evolving?

I have a little place on a lake in Northern Ontario. The lake is about 1 x 3 miles. It depends on rainfall runoff to keep water levels up. It slowly drains into another lake about 6 miles away when water is a plenty....I know this because I try to kayak to the other lake every year but never make it because of shallow areas and too many dead trees and other obstacles. Very peaceful and an amazing place to view waterfowl and turtles. My little lake contains pike and bass with some smaller gamefish. It is basically a mud bottom, 10' down at it's deepest point and has several of what we call cattail islands, floating heaps of dead vegetation hosting several varieties of bushes, grasses and trees. The big fish are under the islands for the most part and the gamefish are found near shore or in some of the few weedy areas out on the lake.

One of the smaller fish is the sunfish. I've fished in a lot of places in Ontario and there isn't a sunfish that I've hooked that wasn't very colorful, bright oranges and greens. However on my lake, every sunfish I've caught is very pale, almost white, with light green vertical stripes up their sides. Even the perch seem lighter in color here than elsewhere. I never thought about it much but after reading Dawkins' Greatest Show on Earth I'm starting to think these sunfish have evolved over the years to this paler color. Am I way off here? Is there a very pale species of sunfish I haven't heard about? Are these sunfish a product of natural selection? Has environment necessitated change? I can't see what the advantage would be if paler. Has anybody noticed anything similar in other isolated lakes they frequent?

it's a possibility that some selective pressure is causing the pigmentation to be bred out of the fish population in your lake - but it could also be an epigenetic effect - in other words there has been no change in the DNA sequence and the fish retain the ability to develop pigment but something in the environment is causing the genes responsible for it not to be expressed or to be expressed differently.

DNA sequencing or a transplanting experiment might yield some results

It could simply be genetic drift. Or a result of the founder effect, a small group of fish with an uncommon trait settled the lake.

The bluegill is also called the "pale sunfish" if that is of any relevance here.
http://warmwaterflyfisher.com/WWspec...tlesunfish.htm
Lepomis macrochirus

Other common names: bluegill sunfish, northern bluegill sunfish, common bluegill, blue sunfish, bluemouth sunfish, sunfish, pale sunfish, chain-sided sunfish, bream, blue bream, bluegill bream, coppernosed bream, blackear bream, roach, dollardee, sun perch, strawberry bass.

There is so much we still don't understand about fish, they are fascinating. I think the documentary Planet earth really taught us a lot about their behaviors and habitats. The show River Monsters on Animal Planet is very interesting when it comes to the evolution of fish.