I was watching a lot of mountain fishing videos and i was wondering how the trout population can remain healthy and genetically diverse if no new trouts enter the gene pool?
In: Biology
very few lakes are truely enclosed. most flow out a river somewhere.
There are a few lakes where a fish gate has been put over the river, these are generally stocked by humans to give people fish to catch.
but its nor like you need that much foe genetic diversity, in general you only need 50 individuals to avoid inbreading, and 500 to avoid gene drift.
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In addition to the other answers you’ve gotten, another thing to consider is that seemingly seperate populations of fish can still mate over generations. Birds can transfer eggs and even live fish from one body of water to another. It was long believed eggs might hitch a ride on feathers or their legs, but studies have shown some eggs will even survive fecal transfer.
Along with the other answers, a big part of genetic diversity comes from just recombining the genes already present in the population.
Random mating-especially common in fish
Random fertilization-which particular sperm cell meets which particular egg cell, creates quite a bit of variety even with the same two parents
Mutations-someone already mentioned this
Random assortment of chromosomes-two egg cells from a single female fish will not be identical
Crossing over (during formation of sex cells)-also increases the variety within one parent’s sex cells
Along with all the things talked about here, lack of genetic diversity does not mean the population is doing to die off.
Almost every animal population on small islands is cut off and incredibly inbred. Yet these populations are doing just fine.
Inbreeding is not ideal, but it’s far from a death sentence.
I’m a fish ecologist in Nevada and a lot of our native fish species are really isolated and most springs and river systems in deserts have many fish species 25% of our native fish species are only found in Nevada. Also, almost every tiny spring has its own species of spring snails in it! Most of these systems were connected during the ice age when Nevada had many large lakes and rivers, but they have been isolated for the last 12 to 15 thousand years.
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