Iowa lakes have been battling a terminal invader introduced by misguided individuals under the belief that it will produce a fish of a lifetime, but in reality it will lead to increasingly poor fishing and, in a few years, an eventual collapse of the lake.
Gizzard shad have shown up in Badger Creek in Madison County, Beaver Lake in Dallas County, Hawthorn Lake in Mahaska County, and twice in three years at Lake Wapello in Davis County. And now, gizzard shad have been found in Lake Sugema in Van Buren County.
"Gizzard shad have been illegally transported and intentionally stocked by ill-advised people, perhaps with the hopes of producing a trophy bass fishery, but instead they are basically destroying the lake," said Mark Flammang, fisheries biologist with the Iowa Department of Natural Resources at Lake Rathbun.
Flammang has been battling gizzard shad in Lake Hawthorn and Wapello during the past few years. Each lake had its water level lowered and fish population killed in order to start over, without any gizzard shad.
"Introducing gizzard shad is not a recipe for a quality fishery," Flammang said. "Introducing gizzard shad will lead every small system to its demise. The individuals who do this are depriving local anglers from fishing opportunities and local businesses from money spent during those fishing trips. Fishing could be basically non-existent for a number of years because it takes time to get a fish renovation planned and money to perform the kill. When we totally renovate a lake, it will be two to three years until fish grow large enough to bring the anglers back."
The local businesses around Lake Hawthorn and Lake Wapello have been missing out on the angler traffic since the shad introduction. At Lake Hawthorn, 32,000 fishing trips produce an average of $160,000 in angling benefits each year in gas, food, bait and snacks. In the time it took for the shad to decimate the fishery, and for the renovation and recovery, local businesses will see about $1.1 million less in economic activity from fishing trips. The DNR will spend $20,000 to renovate the lake.
At Lake Wapello, 40,000 anglers visit each year. Since the fishery has declined, the local economy will lose out on nearly $1.2 million by the time the fishery will have recovered. Since Wapello was stocked twice with shad, the renovation cost $35,000.
Why gizzard shad are so bad for these small systems is not completely understood, but one factor is known. Gizzard shad are more efficient at feeding on plankton than young game fish and will out-compete them for available food. There will be fewer and fewer young game fish coming in to the system until they are squeezed out all together.
"It is not an immediate decline. In the short term the adult bass will plump up. There will likely be good bluegill fishing during the first year, but the bluegill fishery will gradually decline. Bluegills will never co-exist with gizzard shad in our small systems," he said.
"Bass will be impacted, crappies, basically every fish species because shad reproduce in large numbers, grow quickly and are filter feeders over their entire life leaving no food for hatching game fish," Flammang said.
It is illegal to stock fish in any public water of the state, including game fish. The public is asked to report any of this illegal activity to their local conservation officer or by calling the Turn-in-Poachers (TIP) hotline 1-800-532-2020. Callers can remain anonymous.
SHAD TURN UP IN LAKE SUGEMA
At Lake Sugema, Flammang is working on a plan to knock the shad population back before it gets a strong foothold while at the same time not totally killing out the rest of the lake.
Each year nearly 60,000 anglers fish Lake Sugema. If Sugema was allowed to follow the path of Wapello and Hawthorn, the decline and return to quality angling would take five years and cost the local economy about $1.8 million.
"Lake Sugema is a gem in southeast Iowa. It has an outstanding walleye population, excellent bluegill and largemouth bass fishing. We have been stocking muskies in it since 2006 and have fish up to 47 inches. Finding shad in the lake was disheartening to say the least," Flammang said. "Hopefully, we'll have a final plan early next week."
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