Crappies and mastodons shared the same habitat. Crappies are primarily a lake fish, preferring clear still water where they prey on small minnows and insects. Mastodons often waded into lakes to feed upon submerged aquatic plants. Perhaps they even aided crappies by forcing minnows away from the cover of underwater vegetation into the open to be picked off by schools of crappie. Of course, mastodons weren’t as tied to the water as crappies and could travel overland whenever they desired.
Black crappie (Pomoxis nigromaculatus). A beautiful fish and tasty too. I once had a fish dinner of bass and crappie. The bass were meatier, but the crappie were sweeter and better tasting.
Kurt Hamlin, a curator at the Milwaukee Museum, was lucky enough to find fur on a mastodon specimen. The fur resembled that found on river otters and beavers, so we know mastodons spent a lot of time in the water.
River otter (Lutra canadensis) pelt. River otter fur is water proof and dries quickly. Mastodon fur was similar.
Although these two different species shared the same habitat, the fossil remains of mastodon and crappie have been found together at only 1 locality–The Charles Adams Mastodon Site in Livingston County, Michigan. It was a lake deposit also containing fossils of meadow vole, 1300 snail shells, 500 freshwater clam shells, and bones of white sucker fish. In Georgia mastodon fossils have also been found associated with fish remains, but not crappie. An alluvial deposit in Little Kettle Creek contained bones of channel catfish along with mastodon. The deposit in Kingston Saltpeter Cave in Bartow County contained over 500 fish bones in addition to a mastodon fossil. Here, predatory birds brought fish from the nearby Ashpole Creek, a tributary of the Etowah River. They included gar, pickerel, channel catfish, bullheads, sucker fish, chubsuckers, largemouth bass, and unidentified sunfish. Coastal fossil sites often have marine species of fish as well as mastodon.
Overall, fish populations during the Pleistocene were much higher than those of today’s waters. Then the rivers were undammed, unpolluted, and unfished by men. But in what’s now Georgia crappie populations were probably an exception. They thrive in modern artificial reservoirs formed behind the numerous hydroelectric dams. Suitable habitat during the Pleistocene was temporary and sporadic. Oxbow lakes were plentiful during interstaidals and interglacials. Cut off channels were common during stadials. But large lakes akin to modern day reservoirs were nonexistent. Instead, crappies relied on favorable habitats that constantly changed with the evershifting river patterns. They can live in rivers where water flow is obstructed and forms pools. Lower water levels with still channels, and higher water levels with wide bends that form slow moving water both provide favorable habitat. Crappies could also inhabit large beaver ponds. But the constantly changing conditions probably made crappie numbers fluctuate much more than they do in today’s reservoirs.
Centrarchid Evolution
An evolutionary tree of the centrarchid family of fishes as proposed by some scientists.
The centrarchid family of fish includes sunfish, crappie, and bass (though not white bass, striped bass, and sea bass which are in completely different families). The opportunity for speciation occurs often among this family because populations of fish get isolated when connecting streams run dry or become obstructed. This makes the centrarchid family an excellent one for evolutionary scientists to study. Scientists can look at rates of genetic divergence between closely related species and estimate the length of time it has taken since speciation occurred from a mutually ancestral species. They call this a speciation clock. Many species of centrarchids hybridize but genetic compatibility decreases with time since speciation occurred. One study found that hybrid embryo viablity declines 3% per million years of separation.
Here’s a list of centrarchid species which are strictly an American family of fish. Note: Some scientists recognize 33 species and 7 genera; others recognize 31 species and 9 genera.
Mud sunfish–Acantharchus pomotis
Shadow bass–Amploplites aribmarus
Roanoke bass–A. cavifrons
Ozark Bass–A. constellatus
Rock Bass–A. rupestris
Sacramento perch–A. choplites
Blackbanded sunfish–Ennearanthus gloriousus
Flier–Centrarchus macropterus
Redbreast Sunfish–Lepomis auridus
Green sunfish–L. cyanellos
Pumpkinseed sunfish–L. gibbosus
Orange spotted sunfish–L. humili
Warmouth–L. gulobus
Bluegill–L. marochirus
Dollar sunfish–L. marginatus
Longear sunfish–L. megalatis
Redear sunfish–L. microlophus
Red spotted sunfish–L. miniatus
Spotted sunfish–L. punctatus
Bantam sunfish–L. symmetricus
Redeye or Coosa Bass–Micropterus coosae
Spotted Bass–Micropterus punctatus
Largemouth Bass–Micropterus salmonoides
Shoal Bass–M. cataractus
Guadalupe bass–M. treculi
White crappie–Pomoxis annularis
Black crappie–P. nigromaculutus
Redeye bass
A redeye bass.
In my blog entry of a few weeks ago about the food I would eat, if I could live in Georgia 36,000 BP, I mentioned smallmouth bass as a fish I might find in my fish traps on the Broad River. At the time of European colonization of North America smallmouth (aka spotted) bass only occurred in extreme northern Georgia. It did not naturally occur in the Broad River, though it has since been introduced. During the Pleistocene, smallmouth bass may have ranged further south, but maybe not. Instead, redeye bass, a closely related species, did occur on the Broad River. Redeye bass and smallmouth bass probably evolved from a common ancestor that diverged due to the geographical separation of the watersheds where this common ancestor lived. So, I believe I would find redeye bass in my Pleistocene fish traps in the Broad River, and probably not smallmouth.
Reference:
Bolnick, Daniel; and Thomas Neal
“Tempo of Hybrid Inviability in Centrachid Fish (Telestei: Centrarchae)”
Evolution 59 (8) Augusts 2005
GeorgiaBeforePeople 