Tennessee Lake Management and Tennessee Pond Management: Florida largemouth, part II

I wrote in my last post about how badly the catchability difference between F-1s and pure Floridas has been exaggerated. Now I’m going to talk about the biggest reason I recommend pure Floridas instead of F-1s.

There was a time when I stocked F-1s regularly. Most other pond management companies working in this state still stock F-1s almost exclusively. F-1s are raised by far more fish farms in the southeast than are pure Floridas, which makes them much easier to procure consistently; and my competitors are all about doing things the easy way.

We, conversely, have been stocking pure Floridas for our clients who want big bass for over two years now. One of the first lakes we stocked pure Floridas into is a 25-acre lake in Memphis that we began managing in October 2014. We stocked 3,500 fingerling Floridas into that lake in late September 2015. That wasn’t the only thing we did to the lake, by any stretch, and some of the northern-strain largemouth in the lake have already begun getting large via our management: on Christmas day, 2016, for example, a lake resident caught two seven-pound and a nine-pound largemouth. But now that lake has pure Floridas.

When we initially electrofished that lake in October 2014, we only captured two bass over fourteen inches, and only one was over 15”. We electrofished the lake again in October 2017, and captured fourteen bass over 15”, five over 18,” and four over 19,” including one over 20”. The two lake residents that were going out with us that day for the shock survey fished for two hours in the morning before we arrived from middle Tennessee, and caught twelve largemouth from three pounds to five pounds eight ounces. They also happened to tell us that almost every time they fish, they’re catching a lot of bass in the three- to five-pound range, and all of the bass appear young and healthy, which is consistent with the 93% average relative weight we found among all the bass we captured in the survey. It’s impossible to determine for certain without expensive laboratory DNA tests, but it stands to reason that those bass are the Floridas we stocked in 2015. That particular lake has a relatively small yearly budget for fish management, and up until fall 2017, only a fraction as much forage had been stocked during our management as what we often stock in other waters we manage for trophy bass. However, the lake received a large forage stocking this past October, subsequent to us shocking it earlier that month. Suffice it to say, property values on that lake will go up in the next few years as those Floridas mature.

There’s a genetic phenomenon called outbreeding depression, whereby the offspring of hybrids of two species often display inferior traits compared to either parent species. One of the first weakened traits that typically manifests is poor growth potential. This is why many state agencies now caution pond owners against stocking hybrid bluegill, or warn that a pond stocked with them will have to be totally renovated, i.e. poisoned and re-stocked, every four to six years. If you’ve ever fished a pond that had had hybrid bluegill for several years and you caught bluegill that averaged three inches long, this is why.

Some biologists claim that Florida- and northern-strain largemouth are only two separate strains of the same species; but there are also those who claim they are two entirely separate species. Regardless of which is the case, there’s enough difference between the two genetically that anytime they cross, there is the potential for outbreeding depression in their offspring, just as with hybrid bluegill, hybrid crappie, or any other hybrid.

One of the saddest large lakes I have ever worked on is a sixty-acre lake a couple hours east of here. According to a resident on the lake, large bass were common the first few years after the lake was stocked. Neither that resident nor any of the other residents who fish could figure out why the bass size had dropped so precipitously; as I kept asking questions, I found the probable answer, before we ever saw the lake in person. It was stocked with F-1s, exclusively, from the start.

When we electrofished it in October 2017, the largest bass we captured weighed 1.21 pounds. The bluegill-to-bass ratio was 4:1, which is not great, but better than the 2.18:1 ratio we found in a 150-acre lake we shocked that same month that had only pure-strain northern largemouth and yielded five bass over 18” in our survey including one that weighed just under five pounds.

The difference? Those F-1 bass in that sixty-acre lake have been breeding with one another since the lake was stocked in the early 2000’s.

I am not a genetic specialist; I couldn’t tell you all the ins and outs of outbreeding. We regularly stock pure Floridas into lakes that only have pure northern-strain largemouth, and those Floridas are almost guaranteed to interbreed with the northerns. The difference is that the pure Floridas can still choose to breed with other pure Floridas, and when F-1s happen, some of those fish are going to breed with pure Floridas or pure northerns, which should minimize the potential for outbreeding. The best example of how well stocking pure Floridas into a population of pure northerns can work, even after many years, is Chickamauga Lake. TWRA first began stocking pure Florida largemouth into the lake on a yearly basis in 2001; in March 2015, the state record of fourteen pounds, eight ounces that had stood since 1954 was bested by a fifteen-pound, three-ounce bass from Chickamauga. Ten-pound largemouth have become common on the lake, a size that was a true rarity when it only had northern-strain largemouth.

But TWRA isn’t stocking F-1s into the lake – they’re stocking pure Floridas.

Outbreeding depression in F-1 largemouth is by no means my discovery: I’m just passing on to my clients the latest in scientific knowledge on largemouth bass. Floridas are much harder to source, which is why we’re starting our own stock a couple months from now on our fish farm which is currently under construction. Here’s some further reading on the aspect of outbreeding depression as it applies to F-1s: