Most Indiana bassers have spent some time on the Ohio River, both good and bad, I'm guessing. It can be a pretty stingy place at times, and even in good times, isn't all that great. But there is a lot more to the river than the several hundred miles that border our state, and a recent study revealed some interesting fish observations.
The Ohio River is 981 mile long. The river begins in Pittsburgh, Pennsylvania, at the confluence of the Monongahela and Allegheny rivers and flows in a west–southwesterly direction, joining the Mississippi River near Cairo, Illinois. It has been studied quite a bit over history, but one of the first reasonably detailed accounts of Ohio River fishes was provided by a gentleman named Constantine Samuel Rafinesque, who in 1818 traveled the length of the river and described over 20 new species. What might be most surprising to some, was at that time, the river was fairly clear and was dominated by hard substrates except in its lowermost reaches, with shallow-water areas being common in the summer. The most famous shallow-water area was the “Falls of the Ohio” (near Louisville, Kentucky), where Rafinesque spent much of his time during an exploratory trip in 1818.
It's kind of hard to picture the Ohio River as clear and shallow running, as most of us have only ever seen it since the system of locks and dams were put in place. These structures provide commercial navigation through maintenance of a 9 ft. deep channel for the entire length of the Ohio River. These dams have transformed the once free-flowing river into a continuous series of impoundments, and subsequently altering the fish community. There are 20 such lock-and-dam structures on the Ohio River, and most of them have been in place for 40–50 years.
Researchers measured several different physical variables including water temperature, dissolved oxygen (DO), specific conductance, water depth, substrate type, water quality and instream habitat. They then used a series of fishery analysis done concurrently over the entire stretch of the river, and looked for trends in fish populations. Interestingly, these variables explained little of the patterns documented throughout the river in the study, with a couple notable exceptions - more on that in a minute.
First, a quick reference for those not familiar with Ohio River mile markers and locations to give you an idea of locations:
- Tanner's Creek - River mile 493
- Markland Dam - River mile 531
- McAlpine Dam - River mile 615
- Cannelton/Rocky Pt - River mile 721
- Smithland Pool/Golconda - River mile 902
As you can tell, most of Indiana's stretch borders the lower half of the river. Keep that in mind as you read the following findings, broken down by categories.
Category 1 (no trend) -Three species, common carp, gizzard shad, and largemouth bass, exhibited no longitudinal trend (in other words, they were found equally disperesed throughout the entire river). The gizzard shad, which is perhaps the most common fish in the river, comprised 40% of our electrofishing catch and was most commonly collected at CPEs of about 160 fish/mile throughout the length of the river. Common carp, though much less abundant than gizzard shad, were also collected at similar rates over the length of the river.
Category 2 (most abundant in the middle reach of the river) - Sauger, longear sunfish, and skipjack herring were most abundant in the middle river segment (river mile 300–600). For example, longear sunfish showed a distinct peak around river mile 497 and were less abundant in both the upper and lower reaches of the river.
Category 3 (more common in the upper half of the river) - Spotted bass and bluegill were much more common in the upper half of the river. For example, catches of spotted bass from river mile 51 to river mile 450 were typically 12 fish/mi, but in the lower half of the river catch rates were only 2.5 fish/mi.
Category 4 (more common in the upper third of the river) - Smallmouth bass were significantly more common in the upper third of the river.
Category 5 (consistent decline from upstream to downstream). Flathead catfish, freshwater drum, white bass, and hybrid stripers were all more numerous in the upper reaches, with populations declining as you traveled further downriver.
Category 6 (like category 5 but with an increase near river mi 945) - This category included channel catfish. Channel catfish catch rates were 8–24 fish/mi upstream of river mi 248, declined to a minimum of 2.5 fish/mi at river mile 745, and then increased to about 5 fish/mi at river mi 945. The measures all peaked at the upstream end of the study area, reached their minimums at river mi 745, and rebounded at river mi 945.
Category 7 (increase from upstream to downstream) - One of the few fish to "buck the trend", striped bass actually increased in numbers the further downriver you went. Similarly, blue catfish were fairly common near river mi 945, rare to common in the lower half of the river, and essentially absent from the upper half of the river.
Earlier in the post I mentioned some notable exeptions. Tourney anglers might want to take note of this neat fact. The numbers of smallmouth bass and spotted bass found were all directly related to percent cobble/boulder, and were inversely related to percent silt. So though the trend didn't hold up well across the entire river study as a whole, locally, whenever they found various rocky bottom areas in a stretch, they would find the spots and smallies. The more silt and mud in the stretch of river, the less of these two bass. That little tip should help eliminate a lot of water when searching for either of these two fish.
** Longitudinal Variation in the Ohio River Fish Community. North American Journal of Fisheries Management. Greg Seegert, Joe Vondruska, Elgin Perry, and Doug Dixon