I don't think they stop growing or producing eggs as they get older but I'll have to ask a fisheries biologist to get the answer to this question.

I do think that we put pressure on the species and that removing the larger fish MAY have an impact on the gene pool in the fish population. It's a process that scientist call genetic selection. However a big fish may have produced hundreds of thousands of offspring before they are taken out of the lake. So their genes have been passed on to new generations many years before they are caught and taking out of the lake. So the natural selection of fishing pressure may not really deplete the big fish genes out of the gene pool. Thankfully nature found a way to preserve the bigger fish genes for the fish and us fisherman. Nature is pretty cool.

I read a bit in my fish book. The ability of the fish to continue to reproduce depends a lot on the species of the fish and the local environment that the fish live it. Fish continue to grow throughout their life for the most part but the growth rates may slow down in later years. There is a big difference in the life spans of different species of fish. Freshwater vs saltwater fish and even within the freshwater fish. Catfish and Sturgeon can live a very long life vs a minnow that may only live for 2 years tops. I wish that my text book spoke more to the freshwater fish that we seek like Large mouth Bass and Small Mouth Bass.

I think that it would be hard to deplete the gene pool of the big fish genes since we tend to protect these fish when they are smaller which allows them to reproduce a few times before they get harvested.

Regards,

Moose1am