Largemouth Bass Become Snagged in the Food Chain : Lake Mead: There aren’t enough shad, and the striped bass have eaten too many trout. No one has any solid answers.
Lake Mead, past and present . . .
Largemouth bass are hunting shad and growing fat in the shallows of the lake’s many coves. Fishermen are hunting largemouth bass and growing adept at catching them. About 800,000 are caught in 1963, and all seems well.
Largemouth bass soon start to become scarce, for reasons that are uncertain. Fisherman Don Sollberger complains of catching bass with their lips cut and torn, explaining: “They’re rooting around in the loose rocks and gravel because they can’t find any shad.”
In 1969, striped bass are introduced to augment a failing largemouth fishery. The striper becomes king of the lake. The largemouth fisherman is replaced by the striper fisherman. One is Henderson’s Jim Brady, who changed gear and lugged in the lake-record 47-pound striper.
A record 30,000 stripers were taken by fishermen in 1978, and the count skyrocketed to more than 160,000 in ’79. The fishery thrived until the early 1980s, with fish regularly topping the 30-pound mark.
Rainbow trout, a “put-and-take” fishery dictated by the planting schedule of the Nevada Department of Wildlife, are heavily foraged upon by stripers, according to studies. The stocking is stopped, deemed too costly.
The trout disappear, and the stripers become skinny. They can no longer feed on trout, and the shad base--threadfin shad is the primary food base of largemouth and striped bass--is no longer enough to support a healthy fishery, it is learned.
Apparently, the building of the Glen Canyon Dam, 200 miles up the Colorado River, which created Lake Powell in 1963, is a major factor in the lake’s decline as a fishery. Phosphorous, in the form of phosphates leached from rocks in the Colorado drainage area, is settling upstream in Powell instead of making its way downstream to Mead.
Shad are sustained by plankton, which require a healthy level of phosphates and nitrates.
In 1981, the Clark County Wastewater Treatment plant begins an operation in which what is discharged into the water contains fewer phosphates, placing a bigger burden on the fishery.
Dr. Larry Paulson, a freshwater specialist in charge of the Lake Mead Limnilogical Research Center at the University of Nevada Las Vegas, is hired by the Nevada Department of Wildlife to attempt to fertilize a section of the lake--to determine if spot fertilization can indeed be utilized to restore this once-fabulous fishery.
“Trying to grow fish without phosphates,” he says, “is like trying to grow cows on the beach.”
In May of 1987, the largest lake fertilization project ever attempted in North America is initiated. Three hundred boats, each with five-gallon jugs, spread out over the lake’s huge Overton Arm and dump 20,000 gallons of ammonium phosphates over an area covering 20,000 acres.
A moderate algae bloom occurs, and there is a significant response in the zooplankton population, which Paulson says is responsible for an increase of juvenile shad.
It is done again in 1988, and the project seems to be going well. In 1989, another 40,000 gallons of phosphates are added.
The three-year project has recently ended.
Is Lake Mead on the road to recovery? Are three years of fertilization finally paying off?
No, says Paulson.
Either the increase in the production of small stripers in the fertilized area or the immigration of small stripers from infertile areas down the lake is the reason, he says.
The little stripers have become so numerous throughout the lake that any shad being produced are concentrating in the shallow, warmer sections of the lake and being consumed so fast that the big stripers--which reside in the deeper, colder areas--are still left with little to eat.
“The shad are warm-water critters, so in order for the big striper to get a bite to eat, he’s got to come up into the warm water to find the shad,” Paulson says. “The smaller stripers--sub-adults--can take the warm water, so they can spend all their time, or practically all their time, in that warm water, and they have a competitive advantage over the larger fish.”
Furthermore, striped bass, which are supposed to require running water to reproduce, can reproduce in the lake with apparent ease. The eggs that settle to the bottom do not suffocate because the lack of oxygen-depleting nutrients--and algae--in the system leaves plenty of oxygen for the eggs to hatch.
“When you have as much reproduction as apparently occurs in Lake Mead, and so few productive areas--it just can’t handle it,” Paulson says. “Those rascals put such a tremendous pressure on the shad that we weren’t able to sustain them into the full three years of the program.”
As for the restoration of the fishery, Paulson would like to see trout stocked again.
“From a political standpoint, stocking rainbow trout to feed striped bass is not very palatable,” he says. “Biologically, it doesn’t make any difference to the striped bass.”
Rainbow trout, he explains, are an ideal forage for the stripers because they prefer the colder and deeper water the big stripers need, and are too large for the small striped bass to eat.
“The alternative that is most attractive at the present time would be to go back to stocking trout, recognizing that there’s going to be some loss (to stripers),” he says. “One thing’s for sure, if you don’t stock trout, you can be guaranteed of two things: Not having a trout fishery, and not having a striper fishery--that’s guaranteed.”
However, to produce a pound of bass, it takes roughly six pounds of forage fish, according to Dave Buck, fisheries supervisor for the Nevada Department of Wildlife. “There’s no way you could produce enough trout and release enough trout to have any kind of an impact on the total fishery resource--it’s just not practical,” he says.
Meanwhile, upriver at Lake Powell, which is now experiencing similar problems due in large part to dams built farther up the Colorado River, biologists hope to introduce rainbow smelt, which they say will go to the deeper water and provide forage for the larger stripers.
These fish would filter down the river, into Mead and other reservoirs further downstream, and therefore opposition is heavy.
“There’s tremendous opposition everywhere we turn,” says Wayne Gustaveson, a biologist with the Utah Department of Wildlife and chairman of the Colorado River Wildlife Council. “We’re finding people in downstream states, that don’t have a stake in the benefits from introducing the smelt, are opposing it because of the potential impact on threatened and endangered species--squawfish, humpback chub, etc.”
The down side, everyone agrees, is that it costs too much to feed the trout.
But, Paulson says, “You can’t get the stripers out of the (Colorado River) system, we’re stuck with ‘em. The next thing to do is go to the public and say, ‘If we were to charge you people to produce a certain number of trout fully knowing that some of them are going to get eaten by striped bass, are you willing to pay for it?’ And I think you’d see a lot of right hands going up.”
Meanwhile, the department is spending money on other projects, such as crayfish research, with the objective of increasing crayfish in the lake, thus establishing a food base for largemouth bass.
“It’s not easy to come up with a concrete biological solution to the problems of Lake Mead,” he says. “But we haven’t given up. We continue and will continue to try to find some of the answers.”
Meanwhile, Lake Mead, with its 550 miles of scenic shoreline, remains embattled as a fishery, transformed from a largemouth bass haven--they are now less than 2% of the fish caught in the lake--into a war zone in which smaller stripers rule.
“We’ve had a changing clientele,” fisheries biologist John Hutchings said. “For every fisherman who used to come here to catch largemouth bass, there are three more in back of him who come here to fish for stripers.”
And what about the angler who used to fish here for large stripers? “He has been replaced by those who just like to fish,” Hutchings said.
