What’s good for trout may not always be green

December 7, 2007

Photo by Ken ColeRainbow trout are a classic example of what biologists call an “indicator species” — if they are found in abundance in a river it is usually taken as a good sign that the water is clean and the ecosystem healthy. But what if the river in question is the Lower Mountain Fork in southeastern Oklahoma, an area with scorching summers and mild winters where cold-water rainbows don’t naturally reside? The thought crossed my mind during a recent flyfishing trip there in early December. Its deep pools and gushing water offer superb angling for self-styled “trout bums” like myself — which is hardly surprising as it is stocked on a fortnightly basis with plenty of fish. The trout ower their existence here to what at first glance may seem an unlikely source: the local dam. This was bass water at one time but the dam’s construction four decades ago meant the water released from its artificial depths was suddenly too cold for bass. Trout were then brought in, resulting in what is known as a “tailwater.” In the eyes of many, the trout have simply replaced a predator which could not adapt to human-induced temperature change and are therefore not in the same category as “invasive” species which drive out the native critters.  ”The bass were not usurped by the trout, they were replaced by them,” says Ken Cole, a Dallas-based fishing guide who knows these waters well.  I for one enjoy this trout fishery which is about a 3-1/2 hour drive from Dallas and “tailwater” trout are now common in many parts of the United States. But the long-term ecological consequences of this experiment remain unknown and so the green jury is still, I think, out on the practice. ” Photo: compliments of Ken Cole

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