I rant a lot on this blog about wild fish and how important they are but being just a layman I am not eloquent enough to put it layman's terms as to the importance of wild fish . As a matter of fact I don't even try because there are scores of people who know this stuff better than me so the practical thing to do is let them explain it.
I gleaned the following from The Wild Steelhead Coalition website. Whose website is linked in "Friends of the Quiet Pool" column.
All species live in constantly changing environments. To overcome environmental
fluctuations, it is essential for species to exploit all available habitat. The long-term existence of a species is maximized through the adaptation of numerous populations and sub-populations to specific environmental conditions. These adaptations have evolved over hundreds and thousands of generations in concert with a natural, fluctuating environment. As the environment changes so does the composition of individuals within a population.
While the environment acts as a changing variable to individuals within a population, the one constant is that individuals pass their genetic makeup, which includes chromosomes, genes, and non-coding regions of the genome, to their offspring. This inherited genetic material is passed from one generation to the next as the foundation upon which individual uniqueness and population differences are maintained and is known as genetic diversity.The genetic diversity maintained within a species is a genetic reservoir upon which natural selection acts.Populations with unnaturally altered or low levels of genetic diversity can be stripped of their evolutionary future because their ability to respond to changing environments has been reduced. Loss of genetic diversity can lead to reductions in fitness and decrease an individuals ability to adapt to environmental changes. Fitness is a measure of an individuals potential to produce viable offspring. Fitness reductions can be caused by either inbreeding or genetic drift. Inbreeding is often observed in populations with low numbers of mating individuals, and occurs when closely related individuals mate as opposed to unrelated 26 individuals. Inbreeding often increases the frequency of deleterious genes within a population.
A classic example of inbreeding and its effect is the lethal genetic disease hemophilia within the European monarchies, most notably Queen Victoria of England and her descendants.