ブラックバスの種類は19種類まで増えた!?

The first fish classified as a largemouth bass and bestowed with the Latin name Micropterus salmoides most likely was not a largemouth bass, according to fisheries scientists who recently completed a comprehensive study of the evolutionary and genomic history of black bass.

This error was more the result of the limitations of the time than sloppy science. The determination was made based on samples taken around Charleston, S.C., in 1802 before other species of black bass were known to exist. But now Andrew Taylor from the University of Central Oklahoma and his associates believe that fish was a Florida bass.

Their revelation concurs with research by Auburn biologists, who asserted the natural range of Florida bass extends far beyond peninsular Florida, as had been generally accepted for decades.

“Imagine our surprise, then, as we began to see fish that we assumed were largemouth bass along the Atlantic coast of Georgia, South Carolina and North Carolina be assigned with great certainty to [be] Florida bass,” said Taylor.

“It turns out that the scale counts used by Bailey and Hubbs [who described a Florida subspecies of black bass in 1949] must not be very reliable in distinguishing the two species, and this changes the known natural distribution of the two species.”

Additionally, he added, that means Florida bass now should be known as
M. salmoides, while largemouth bass should be renamed M. nigricans.

For their report titled “Phylogenomics and species delimitation of the economically important Black Basses,” Kim Daemin and Thomas Near teamed with Taylor to analyze the DNA of 394 specimens from all the black bass species. They and their colleagues collected some samples in the field between 2002 and 2020. Others they obtained from museums and wildlife agencies.

They then constructed a time-calibrated species tree dating back millions of years to explain the evolution of 19 black bass species, including 14 described species, three that are well-known but lack description and two that Taylor said “are new to science through this paper.”

“This study showed that largemouth bass are part of a species complex, which wasn’t known before,” said Yale’s Kim. “It made me realize that largemouth bass were stocked throughout South Korea and East Asia, but they don’t actually know what specific species they are dealing with. Our work can help address this issue and support better management and conservation.”

Those complexes include largemouth, smallmouth, spotted and redeye bass. Additionally, Suwannee bass and shoal bass diverged from the rest as distinct species millions of years ago.

Well into this century, the shoal bass was believed to be a variety of redeye bass. But Taylor said, “Our phylogenomics actually show they do not belong with the redeye species complex. The shoal bass shares close relatives with the smallmouth complex, redeye complex and spotted bass complex.”

Smallmouth discoveries
Of interest to anglers is that the biologists say those two “new to science” species belong to the smallmouth bass complex, which also includes the smallmouth bass and Neosho bass. One of those undescribed species inhabits the Little River system in southeast Oklahoma, while the other lives in the Ouachita River system in southwest Arkansas. Both river systems begin in the Ouachita Mountains and are tributaries of the Red River.

To thrive, both species require cool, fast-flowing streams with pools and riffles, the scientists said, but both are suffering because of habitat lost mostly to agriculture. Conservation efforts are needed to save both, Kim said, as their habitats have been reduced to only a few upstream tributaries in those rivers.

Of the Neosho, Taylor said, “We think that there’s enough evidence now that this fish should be its own species.

“We once believed that it was just a local variety of smallmouth. But then rivers were dammed to make lakes like Tenkiller and Grand and we assumed that those fish would do well.”

That assumption was based on the fact that river smallmouth bass in the Cumberland and Tennessee rivers thrived in impoundments.

Smallmouth bass from the Neosho River system, however, “did not take” to impoundments, Taylor explained.

“And now that makes sense. The Neosho is not ecologically identical to the smallmouth. The Neosho must spawn in streams, and it has a different longevity. We provide a blueprint for what we believe the differences are, but we need to know more.”

Generally, the Neosho is more streamlined and lighter in color than the smallmouth, without the “tiger stripes.”

“But more can be done to help anglers distinguish them,” the biologist added. “Right now, it’s mostly a matter of, ‘Where did you catch it?’”

Additionally, the three well-known but undescribed species include Bartram’s bass and Altamaha bass in the redeye complex and Choctaw bass in the spotted bass complex.

Because so many of these lesser-known fish inhabit streams of the Southeast and Middle Atlantic, their preservation is threatened more than ever these days because anglers illegally have released the Alabama bass into so many reservoirs.

“If you put that fish in a lake, it doesn’t just have consequences for the lake,” Taylor said. “Alabama bass are especially good at moving upstream. They spread like wildfire. They are common now in the Savannah River system, and they probably originally were released into just one or two lakes.”

While in those impoundments, meanwhile, Alabama bass hybridize with smallmouth bass, destroying the genetic integrity of those fisheries, and often outcompete largemouth for forage and habitat.

“The less we move fish, the more protected they are and the better it is for them and for us,” the scientist said.

Want to catch as many of these bass species as possible? Taylor suggests you start with the Guadalupe bass in central Texas and then move eastward.

“Each species presents a unique angling challenge and, since they all don’t live in lakes, you can’t use your bass boat for all of them,” he said. “But some of the places where these bass live are among the most beautiful places on earth.

“The Southeast is a hotbed of diversity for black bass,” Taylor continued. “And that corresponds with freshwater fish in general.

“What’s disappointing is that, with all that diversity, there’s also trouble because some of these fish are imperiled. What would be really good with this report is to generate angler interest and gain some traction to help protect these fish and their habitat.” Taylor recommended, “Agencies and NGOs [nongovernment organizations]that work with landowners to ensure forested stream buffers remain intact can help keep stream hydrology and spawning substrates intact. Similarly, if there are sections of undammed and unaltered riverine habitat, working with management agencies, NGOs, fishing clubs and riverkeepers can ensure that habitat remains relatively unaltered so that these streams can continue to support healthy, naturally reproducing populations.”