Picking up where we left off last week, this week I’m going to flip the switch and talk about the potential negative consequences of stocking. I highly recommend that those who missed, or maybe just don’t remember, last week’s post start there before continuing. Some lingo and concepts may be a little fuzzy without the background information.
You didn’t press the back button, did you? (I don’t blame you, I wouldn’t either). So, here’s a quick refresher: wild trout populations have genes that are locally adapted to their native environments. This means that trout have genes that make them successful at life in their home stream, but their genes may not be great for surviving in another stream. However, not all fish in a stream can be identical clones of one another. There needs to be some level of genetic diversity in order for populations to survive disturbance and be able to adapt to future conditions. I call this the “eggs in many baskets” insurance policy. The genes that are best this year may not be the genes that are best next year, and so there needs to be high diversity so that at least some fish can survive and reproduce if conditions change in the future (if you’re a financial guru, this concept is very similar to having a diversified stock portfolio).
Easy, right? Well, here’s some of the ways that hatcheries can disrupt this balance. I’m focusing specifically on recreational stocking programs because conservation stocking programs have taken more precautions to avoid these potential pitfalls (though, they do sometimes still happen).