Want walleye in southwestern Pennsylvania? Aim for the Allegheny River. But if you're a sucker for smallmouths and sauger, move over to the Mon.
For more than 25 years, the state Fish and Boat Commission has conducted fish population surveys in the tailwaters of regional locks and dams. But a research project that began in 2003 as a survey of baseline water quality indicators on the Monongahela River has evolved into a long-term comprehensive large river assessment program charting game and nongame fish populations at tailwaters in the Three Rivers region.
By focusing on tailwaters, which are generally among the best fish habitats, and revisiting 17 fixed points over a period of years, the Three Rivers Locks and Dams Tailwaters biologist report is slowly amassing what may be seen as the best fishing report ever compiled on these waters.
In its 10th year, the project is still in its infancy -- only 11 of the 17 sites have been charted at least once. But Fish and Boat biologist and regional fisheries manager Rick Lorson said enough comparative data has been collected for the resource to be a useful tool for anglers.
"Bear in mind that [the surveys] are still being done at different locations, and it's important to get a benchmark at all 17," he said. "But we have three locations -- Dashields Dam on the Ohio River, Freeport on the Allegheny and Maxwell on the Monongahela -- where we've visited multiple times. Two surveys are enough to make some kind of assessment -- that's standard protocol."
Annual surveys are conducted at night, mostly in May, using boat-mounted electro-fishing equipment. A "transect," or measurement, lasts for 50 minutes and parallels each bank, and each run extends from the lock wall downstream approximately 1.5 miles.
Temporarily stunned, some of the fish float to the surface and are netted. Numbers of game and nongame species are documented, as well as the length, weight and age of game fish including smallmouth bass, walleye, sauger, freshwater drum, white bass and rock bass.
Later, biologists combine the catch-rate analysis with other data to estimate the overall population as well as numbers of legal-length fish for each species at each survey site. Apples-to-apples comparisons can then be made by analyzing data from multiple years. Part of a water-quality index and fish management tool for Fish and Boat, the surveys are posted on the agency's website for use by anglers (see below).
Knowing how to read the surveys could mean the difference between tight lines and a lot of unrequited casting. For instance, one chart shows that this year's survey found 121 smallmouths in the Allegheny River at New Kensington, 53 smallmouths in the Mon at Charleroi, and 70 smallmouths in the Ohio at Monaca.
"That's the total," said Lorson. "What anglers should look at is legal-length fish."
Of the 121 smallmouths sampled at Allegheny Lock and Dam No. 3, only 21 were legal. Significantly fewer smallmouths were documented at the Ohio River at Montgomery Dam, but 50 percent of those fish were of legal size.
"I'd want to fish on the Ohio at Montgomery," said Lorson.
Analysis of data collected over time tells another story. Over the past 25 years, the Allegheny River from The Point to Freeport has produced the highest catch rates for smallmouth bass. But the Monongahela River has grown more legal-sized smallmouths than the other rivers.
During the same period, the lower Allegheny produced higher catch rates for all walleye and legal-size walleye, but the more silty Mon produced more legal sauger. In fact, the Monongahela River has the most productive sauger fishery in Pennsylvania.
"In the Mon the pools are longer and deeper, and the water is more turbid, more suited to sauger," said Lorson. "There may be lower numbers in the Allegheny, but it still has a good number of legal-length sauger. Overall, your best bet for walleye is the Allegheny, and sauger and smallmouths are best in the Mon."
The survey's white bass catch rate on the Allegheny and Monongahela slumped far below the 11-year mean rate of six fish collected per hour. But on the Ohio River the collection rate spiked to an average of more than 15 per hour. Lorson said that could be due to the cyclical nature of white bass spawning runs. Though generally under-fished, this spring the few anglers who targeted white bass at the mouths of Ohio River tributaries cleaned up -- some reported catching scores of football-sized white bass and hybrid striped bass in a single night.
Multi-year analysis of the surveys shows a weak rock bass fishery on all three rivers. But the under-appreciated freshwater drum is growing in population, particularly on the Monongahela where the state record of 19 pounds 4 ounces -- a significant haul in any species -- was caught in 1994.
The key, perhaps, to legal-length game fish populations is the yearly success of baitfish, and below the surface each river is like another world. In the 2013 electro-fishing surveys, minnows of various species made up 38 percent of the collection at New Ken on the Allegheny River, and 48 percent at the Charleroi Locks and Dam on the Mon. But on the Ohio at Montgomery, minnows comprised just 14 percent -- 39 percent of the total fish collected were suckers.
Lorson said it's too soon to tell if 2013 will be a banner year or a bummer for Three Rivers anglers.
"We don't know yet," he said. "I'd predict there should be a good number of both emerald shiners and gizzard shad. That's consistent with water conditions without a lot of rainfall in most of May and June up until the last couple of weeks."
Read the report at www.fish.state.pa.us. In the search box, type "Three Rivers Locks and Dams Tailwaters."