Good question! And to answer your own question, the answer is "yes"4liters wrote:How come the colour of the yellowbelly varies so much from fish to fish? Is it to do with the water clarity?
According to the Encyclopedia of Australian Fishing (1979), p.1103:
There is some variation in the colour of these fish and it can be related directly to the colour of the waters in which they live. In the perennially muddy rivers of the plains country of western New South Wales, Queensland and South Australia golden perch take on a very light beige colour. Usually there is only a hint of yellow on the body and a deepening of body colour between the lower and upper surfaces.
Sometimes the back is olive green; this may become very dark in specimens from water which is nearly always clear; it lightens to a bluish tinge in fish from semi-clear rivers and dams. Fish that have lived for some time in clear water mostly have a deep golden belly area, but if the turbidity of the water increases they may lose their rich colour. Clear water fish often have a crimson tint around the fins, particularly the pectorals. This conditions appears most common in male fish at spawning time.
So basically, if the water is muddy they will take on a very light appearance; conversely, if the water is very clear they will take on a more dark appearance.
Although this doesn't really explain why there is so much colour variation in fish from the same body of water! But having said that, the Yellowbelly from the lake are generally a lot lighter than the ones from the river, giving credence to the information contained above.
I have included a photo of a Yellowbelly my mate caught in the Wimmera River in December 2012 which is a real dark olive-green colour, again further highlighting the natural colour variations in this fish...