A catfish competition in the Yadkin River has two native species fighting for survival in a river where they were once found in abundance.
Snail bullheads and flat bullheads, also known as mudcats or yellow cats, have declined significantly throughout the upper Yadkin River, due to the introduction of the non-native flathead catfish — a voracious predator that has an appetite for bullheads.
Fisheries biologists with the N.C. Wildlife Resources Commission recently completed a series of electro-fishing surveys in Surry, Yadkin and Wilkes counties and found that bullhead catch rates near Elkin had declined from a high of 120 fish collected per hour in 2005 to less than three fish collected per hour in 2012. Similar collection rates at an upstream site in the Ronda community have decreased from nearly 300 fish per hour in 2005 to 20 fish per hour in 2012.
Biologists have documented an even more extreme decline of bullheads in the Yadkin River below Idols Dam near Winston-Salem, where flathead catfish have been present for decades after being introduced into High Rock Lake downstream. No bullheads have been collected from this section of the Yadkin River since the 1980s.
Idols Dam historically had served as a barrier to help keep flathead catfish out of the upper Yadkin River, according to Kin Hodges, a fisheries biologist with the Commission. Because of this, bullheads had remained plentiful above the dam, until recently.
These latest survey results from the upper portion of the river confirm what Hodges and other biologists have long suspected — when flathead catfish are introduced in a river system, other fish populations decline significantly, either through direct predation by flathead catfish or through indirect competition for food. Bullhead catfishes, especially, seem to be susceptible to flathead catfish predation.
“Sharp declines in bullhead abundance have been documented in other river systems in North Carolina and throughout the southeast where flatheads have been introduced,” Hodges said.
Flathead catfish are the dominant predator in waters they inhabit, eating mainly live fish. Although they prey heavily on bullheads and other catfishes, shad and sunfishes, studies have shown that flatheads will eat just about anything, including carp and crayfish. As a result of their opportunistic feeding habits, flatheads commonly reach weights of 20 to 30 pounds in North Carolina. The current state record, caught in 2005 in the Cape Fear River, tipped the scales at a whopping 78 pounds.
Snail bullheads and flat bullheads, on the other hand, are much smaller catfishes that typically weigh a pound or less. Until flathead catfish were introduced into the Yadkin River, bullheads were the primary catfish species in the river and a favorite target of anglers because they were plentiful, easy to catch and good to eat.
Because flatheads are not native to North Carolina waters east of the Blue Ridge Mountains, biologists speculate that they have been introduced mainly by anglers who want to increase fishing opportunities for a large and hard-fighting fish.
While, on the surface, it might seem like a good idea to replace a population of small bullheads with significantly larger flatheads, Hodges warns that most anglers are likely to see their fishing prospects worsen.
“For starters, like most catfishes, bullheads are generalist feeders that can be easily caught by bottom-fishing with almost any sort of natural bait, while flathead catfish primarily feed on live fish,” Hodges said. “This makes flatheads less likely to be caught by anglers using traditional catfish baits such as nightcrawlers, shrimp, cut bait, chicken livers and other popular catfish baits.”
Anglers also are less likely to catch a flathead because flatheads are much less abundant in rivers than bullheads, owing to the fact that predator species like flatheads always occur in lower densities than prey species such as bullheads.
Unfortunately, once a non-native species becomes established within a river system, very little can be done to mitigate the impacts.
For this reason, the Wildlife Commission in 2005 passed a regulation that required anyone interested in stocking a public, inland fishing water to obtain a stocking permit first. The requirement protects native or legally established aquatic species from the potentially damaging effects of unauthorized stockings by allowing the Commission to assess, on a case-by-case basis, the impacts a proposed stocking may have on an established fishery.
“To prevent episodes like this one from playing out in other water bodies across the state, it is imperative that anglers do not release any species of fish into streams, rivers or lakes where they were taken,” Hodges said. “The introduction of exotic fish species into North Carolina waters is among the most significant threats to populations of both game fish and non-game fish alike.”
For more information on fishing in public, inland waters, visit www.ncwildlife.org/fishing.
Logo courtesy North Carolina Wildlife Resources Commission