What was the fishing like during the Pleistocene?

I’ve often wondered what the freshwater fishing in Georgia waters would have been like before people. Aside from a passing reference with no citation in a book about Archaic Indians, I’ve been unable to find any information about possible extinct species of Pleistocene fish. Fish bones are not rare in the fossil record, but it’s difficult to discern the difference between species, and when Ice Age fossil fish specimens have been identified, invariably they’re attributed to species still extant. Accordingly, fish did not suffer a mass extinction event, but there probably are a handful of as of yet unknown species that did become extinct.

Without human fishing pressure, pollution, and dams that interfere with spawning, fish populations must have been very high and diverse–the composition varying with changes in river patterns and habitat. There were two main alternating cycles of climate during the Ice Age. Cool, arid times occurred when the Laurentide glacier expanded, locking up more water in the atmosphere, creating droughts that lowered the water table. Rivers, swamps, and wetlands shrank in size, but the ocean receded farther to the east, and the fresh water rivers excised valleys over land that are visible today underwater. Actual river habitat expanded, but oxbow lakes and swampy habitat decreased as the rivers became more braided. Rivers were more like chains of many branched channels, some interconnected, some separated by sand dunes. Conversely, during meltwater pulses when the Laurentide glacier melted and retreated, more moisture existed in the atmosphere, creating rainy conditions that filled up the rivers which would begin to meander again, forming oxbow lakes, wetlands, and swamps.

To contemplate Pleistocene fish, I’ve been studying Fishes of the Middle Savannah River Basin by Barton Marcy, Dean Fletcher, and F. Douglas Martin. It’s a fantastic book. Too bad there’s only one copy in the entire east central Georgia library system. I had to request an interlibrary loan to get the one I’m studying. I learned many interesting and surprising facts about the local fish fauna.

–Brook trout naturally occur in the headwater streams of the northern Savannah River, but not in the Middle Savannah River Basin (MSRB) where the water is too warm for this species to exist. During the Ice Age, I suspect waters were cool enough for them to survive, possibly as far south as the Augusta shoals. I also theorize muskellenge lived farther south during the Ice Age.

–Historically, lampreys, that primitive parasitic fish that attaches itself and feeds on bigger fish, occurred north of Augusta. This species hasn’t been recorded recently here–a possible victim of decreased water quality.

–The EPA recommends not eating fish caught in the Savannah River. Too much mercury originating from coal power plants located in the northern industrial states has been deposited in the river. Fish living in the Savannah River Plant creeks and ponds are also radioactive. This is another reason why I long for the days before people–we can’t even eat good freshwater fish.

–Flounder, hog chokers, mullets, tarpon, and needlefish–all ocean fish–swim up to the MSRB seasonally and are common here during some times of the year. This surprised me.

–The bluehead chub is an interesting keystone species. Many other species, such as the yellowfin shiner lay eggs in their nests which the chubs vigorously defend. This is more of a symbiotic relationship than a parasitic one because the increased number of offspring dilutes predation by other fish.

–Sturgeon are endangered from overfishing and habitat loss. Fishery biologists stocked them in the Savannah River, but these stocked fish didn’t always imprint on the Savannah River and were found in other rivers.

–Longnose gars are symbiotic nest associates with small mouth bass.

–Eels can travel over land during moist nights to reach other waterways.

–Quillback suckerfish are related to and look just like buffalo fish.

–The population of white catfish actually declines when humans clean up water conditions. This allows different species of fish to return and compete with them for space. Catfish are more tolerant of pollution than other species.

–Swampfish are a nocturnal species that prefers acidic swampy waters. They’re a member of the cave fish family, some of which live in underground well water.

–Top minnows can respirate in oxygen rich surface water, enabling them to survive in oxygen poor environments.

–Mosquitofish are related to guppies and killifish. They bear live young. They eat mosquito larvae and parasites that they pick off alligator skin.

–Many species of bream, such as the pumpkinseed sunfish, have smaller parasitic morphs that spawn in larger males’ nests. They sometimes accomplish this trickery by mimicking females. Parasitic morphs occur frequently in overfished waters and are evidence supporting the theory of evolution.

–The Christmas darter has red and green stripes–the colors of Christmas.

–Yellow perch are not native to the Savannah River, the southern limit of their natural range is the Santee River. However, they have been successfully introduced. They probably also occurred in the Savannah River during the Ice Age because there is a disjunct natural population in the Mobile delta in Alabama. Yellow perch begin dying when water temperatures get too high. I theorize a dramatic warming event during the early Holocene extirpated them from the river.

–The hog choker, a small species of sole that probably tastes good, used to be discarded by pioneer farmers who fed them to the hogs. The hogs had trouble swallowing the tough scales, hence the name.

Pleistocene fish fossils have been recovered in Georgia from Kingston Saltpeter Cave, Little Kettle Creek, and most coastal sites. Incidentally, kettle is an archaic word meaning fish trap.


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