Bass stocking can remedy habitat loss, but is it the best solution?

Following up on anglers’ complaints of declining bass fishing, Kentucky Department of Fish and Wildlife Resources fishery biologists found fast-growing, healthy largemouth bass but low abundance of young fish.

Habitat assessment revealed heavy siltation in the off-river embayments where largemouth bass spawn. Largemouth bass are quite adaptable and can spawn successfully under a variety of less-than-ideal conditions, but the thick accumulation of unconsolidated sediment was deemed the likely cause for reduced spawning.

The solution of choice would be to remove the sediment in the spawning areas, but that solution was expensive and not compatible with water-level requirements for commercial navigation.

Artificial spawning structures were tested and found to improve spawning success, but installing enough structures throughout the Ohio River was not possible.

Kentucky Fish and Wildlife managers elected to evaluate stocking.

Two-inch long largemouth bass fingerlings were stocked at 100 fish per acre into six embayments ranging in size from 57 to 382 acres. All fish were marked so biologists could tell stocked from wild-spawned fish during future sampling events.

Catch rates of age-0 bass increased substantially after stocking, and 47 to 79 percent of age-0 bass collected throughout the four-year study were stocked fish.

Clearly, the stocked fish were adding bass to the population, and the high percentages of stocked bass validated the conclusion that poor spawning success or survival of early life stages was affecting bass abundance.

Of much greater significance was the finding that the stocked fish survived beyond their first summer and recruited to the fishery. Among the stocked embayments, 46 to 75 percent of bass larger than 8 inches were stocked fish.

While this stocking effort was successful, supporters of stocking programs must not overlook the cost. Stocking just a few of the many spawning embayments required more than 100,000 bass fingerlings. That many large fingerlings would cost about $20,000, but that many fish also is a substantial portion of the output of a large fish hatchery.

Continuing this program will put a significant drain on the agency’s budget and hatchery facilities.

I share this story because I enjoy heralding fishery management successes, but also because this management solution clearly demonstrates three important points that anglers need to understand.

First, determining the need for stocking and then evaluating its success or failure is a necessary but involved and expensive process.

Second, stocking is expensive. Kentucky only stocked several of the many spawning areas, and this program will require substantial expansion to improve bass fishing up and down the Ohio River. And sustaining the improved bass fishing will require continual stocking.

The third point is that habitat loss can ruin a fishery. In this example, the habitat loss was the result of sedimentation — an accumulation of eroded soil in bass spawning areas.

Excessive sedimentation is not unique to the Ohio River. For example, a series of dams and rock wing dikes constructed during the late 1960s and early 1970s converted the Arkansas River into the McClellan-Kerr Navigation System to provide commercial navigation from the Mississippi River to Tulsa, Okla.

Areas of aquatic habitat decreased by 9 percent throughout the Arkansas reach of this waterway during the first 26 years after it was completed. The greatest losses were in dike field (29 percent loss of area), secondary channels (old river channels paralleling the navigation channel, 23 percent loss of area), and backwater embayment habitats (10 percent loss of area).

These are the habitats where anglers fish, and they fish there because that is where the fish live.

Further, much of the remaining aquatic area in these three habitat types was less than 3 feet deep as a result of sedimentation.

A similar loss of habitat is occurring in Mississippi’s Tenn-Tom Waterway. From the mid 1980s when the waterway was completed to 2003, aquatic habitat has shrunk by 5 percent. The greatest habitat loss was in Aliceville Pool (11 percent) followed by Aberdeen (10 percent) and Columbus (8 percent). Similar to the habitat loss in the Arkansas River, greatest losses were in backwaters and cutoff bendways.

Arkansas is making efforts to restore backwater habitat and evaluating bass stocking to improve bass populations.

Sedimentation in the Tenn-Tom lakes has not progressed as far as in the Ohio and Arkansas rivers. I don’t have a crystal ball that sees the future, and I can’t predict if and when siltation of shallow-water habitats will adversely impact bass recruitment and the recruitment of other fish like crappie and sunfish that also spawn in shallow, protected areas. But I’ll take anybody’s bet that sediment-driven habitat loss won’t reverse itself without active management.

Clearly, conserving and, if necessary, restoring the spawning and rearing habitat is necessary to sustain good fishing and a more economical solution in the long run than stocking.