The coldest phase of the Wisconsinian Ice Age lasted from about 28,000 BP-15,000 BP. Much of earth’s atmospheric moisture became locked in glacial ice. For southeastern North America this meant a much more arid climate than exists today in the region. Vast stretches of desert scrub grassland separated stands of open oak and pine woodlands. Rivers shrank in size and were braided in pattern. Modern day rivers in the south tend to meander all over the river valley, but braided rivers didn’t have as much water and had a greater distance to flow because the Atlantic Ocean had receded far to the east. Braided rivers tended to stay within a narrow course.
A modern day braided river in Alaska. Most rivers in Georgia had a braided pattern like this during the Last Glacial Maximum ~28,000 BP-~15,000 BP.
During excessive periods of drought, Ice Age braided rivers held particularly low water levels. Many channels became isolated by sandbars. Shallow channels completely dried, while deeper cut-offs held water that was muddy or silty and polluted. Catfish are known to outcompete other species of fish in polluted water with high siltation, high turbidity, and low oxygen levels. Therefore, I hypothesize, catfish were likely the most common fish in most of the Ice Age braided river systems of southeastern North America.
One might ask how waters could become polluted in a pre-human environment. Man is not the only animal or agent that pollutes water. When droughts occur in Africa, large populations of animals congregate around shrinking water holes. They defecate in the water, and sometimes even die and fall in it. Excess nutrients from the manure cause algal blooms that lower oxygen levels. Moreover, the animals wade through the water, increasing turbidity as sediment becomes suspended in the water. Oftentimes, catfish are the only species of fish able to survive in this toxic slew. I hypothesize the same held true during dry climatic phases of the Pleistocene in southeastern North America. The grassy desert scrublands held large herds of mammoths, bison, and horses that were attracted to the reduced number of water sources.
Pete’s Pond in Botswana, Africa. Note all the game trails leading to the pond. Water holes where megaherbivores congregate are highly polluted with E. coli bacteria. Catfish, particularly those in the Ameiurus genus, are able to tolerate waters polluted by megafauna and were likely the most common fish in Ice Age Braided Rivers of southeastern North America.
Bullhead catfish, members of the Ameriurus genus, are notorious for being able to survive in low oxygenated mudholes. There are at least 5 species in this genus native to southeastern North America–the white catfish, the black bullhead, the brown bullhead, the yellow bullhead, and the snail bullhead. Many sources wrongly categorize these as trash fish. The bullhead catfish is the best tasting catfish I’ve ever tasted with a better texture than farm raised catfish, but I caught mine in a clear canal located in Florida. Reportedly, they have a muddy taste, but I attribute this to specimens caught in muddy water. When caught from fresh clean waters, they taste as good or better than most other species of fish.
White catfish (Ameiurus catus). Still today one of the most common fish in southeastern rivers. It’s a tough survivor capable of enduring polluted water. Water polluted by megafauna manure was common during much of the Pleistocene and especially during stadials.
Brown bullhead (Ameiurus nebulosus). This is the best tasting catfish I ever ate, yet some consider it a trash fish that tastes like mud. I guess it all depends on the quality of water within which the fish lives. Bullheads that live in mudholes probably do taste like mud, but they are just as good as any other fish when taken from clean water.
Channel catfish (Ictalurus punctatus). Unlike bullhead catfish, this species prefers clear sandy bottoms over muddy beds. Pleistocene-aged fossils of this species have been found in Little Kettle Creek, Wilkes County, Georgia. This is the species that is commercially raised and sold in grocery stores.
Upland fossil sites with freshwater fish are relatively rare in the region. Fossil bones of bullheads have been found in Kingston Saltpeter Cave, Bartow County, Georgia where they were probably brought by avian predators. Channel catfish bones excavated from Little Kettle Creek had growth rings, indicating they lived when winters were cold enough for them to go dormant. Modern day winters in central Georgia are not cold enough for fish to go dormant, and their bones do not have growth rings.
Blue catfish and and flat-head catfish are native to the Mississippi River drainage and formerly only occured in Georgia in the extreme northwestern corner of the state, but they have been introduced to other river systems here. Scuba divers report seeing 300 lb. blue catfish near the Clark Hill dam. Flathead catfish may be reducing populations of redbreast sunfish and othe species where they’ve been introduced. Unlike bullheads, these 2 large species require more oxygenated water.
Other species of fish able to survive in poor quality waters alongside bullhead catfish include green sunfish, white suckers, freshwater drum, and mud minnows (Umbridae). Fossils of white sucker fish were also found in Kingston Saltpeter Cave, while Pleistocene-aged fossils of freshwater drum were found in Baker Bluff Cave in Tennessee. Curiously, green sunfish are abundant in Woodbridge Lake in Evans, Georgia where I occasionally fish. This lake is highly contaminated with E. coli, thanks to an overpopulation of Canadian geese.
Eventually, Ice Age droughts ended, water levels rose, and muddy cut-off channels were flushed with freshwater. Other species of fish moved into new territories, and catfish numbers dropped because they were forced to compete with a wider variety of fish in the cleaner water.