Science: Florida Bass Up North

If you live in the northern part of bassin country, you’ve inevitably heard somebody mention how they should just stock some of those Florida strain bass up here to get us some big ones just like they catch down south. Sounds like a good plan, except for the part about how it won’t work.

There have been several studies done over the years to see how Florida bass handle northern climates, as well as testing the genetic offspring of the two (hybrids). What they’ve found is that you get no benefit, and might actually do some harm to the local fishery by trying to do so. Here are some findings from those studies:

• Overwinter survival of northern largemouth bass when tested in central Illinois was much greater than that of Florida largemouth bass. The Florida’s died out at a rate of about 60-80%+ every winter, sometimes less, sometimes more depending on winter’s severity. The northerns always survived to the tune of a 95% or better rate.
• The reciprocal F1 hybrids had a level of survival that usually fell somewhere between the two parent species. In another similar study, mortalities were 48% for Florida bass and 4–5% for Florida hybrids, compared with zero for the northern fish and the northern hybrid, when fish were subjected to a severe cold shock.
• Northern largemouth bass exhibited greater second- and third-year growth than the Florida largemouth bass, so even the young fish that survive if you were to stock Florida’s would grow no faster during their first several years of life.
• Both species have also been tested for their responses to 12–24 h of net confinement. After 7 days of recovery, only 12% of the Florida fish were alive compared to 96% of northern fish and 31–81% of the hybrids.
• Assuming you stocked pure strain Florida bass in your northern lake, if and when they did reproduce with the northern strain bass, you’d end up with a population of hybrids that carried those crossed genes with them, ultimately transferring some of both sets of genes to all future reproductions. As such, you could easily dilute the gene pool of your pure northern strain bass after a period of many years, to the point where a lot of your population of bass could be affected. Survivability and fitness of bass would most likely suffer compared to northern lakes without any introduced Florida’s.

Take home message is that while it always sounds intriguing to put giant Florida bass genes up north, in reality, it’s probably a failed experiment waiting to happen in most cases. If you want Florida bass, you’ll probably have to fish south of a line from Oklahoma to Tennessee and over to Virginia. Those are about the northern limits of successful hybrids.