Giant BassFor fish, size is relative. A small lemon shark tips the scales at 100 pounds while a massive pumpkinseed pushes a pound. Within each species, a combination of nature and nurture fosters growth and at the same time limits it. This sizing process is the ongoing force of natural selection, a process by which biological traits become more or less prevalent in a population, as a function of the effects of inherited traits on the differential reproductive success or organisms interacting with their environments. In other words, creatures that survive and reproduce tend to pass along their traits to the next generation. This process is the key mechanism of evolution. In describing it in On the Origin of Species in 1859, Charles Darwin pointed to its opposition to artificial selection or selective breeding, which had become common at the time in agricultural societies. For the largemouth bass, the diverse environments where the species now lives have helped shape its size. Important environmental effects include water temperature, which affects growing season, as well as other weather effects, forage base, predation (including angler harvest and mortality) competition, and water quality.

In Minnesota, female largemouths reach a typical maximum size of about 6 pounds, males about 3 pounds. That’s about two thirds of state record size. In Florida and Texas, you can double that size for females and add a pound or so for males. In California, females reach greater size, while the largest males are generally smaller even than those in Minnesota.

A bass that grew as large as a goliath grouper, or even a redfish would not be a successful creature. Natural selection has limited their size due to prey availability, reproductive behavior, competition, and other factors we do not understand, all co-evolving over the millennia.

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