Cue the theme from "Jaws," because the Minnesota Department of Natural Resources is again bracing for an invasion of Asian carp.
The threat is real, said the DNR, which recently released a report to the Legislature on the impending arrival of the non-native, destructive fish. Among the recommendations are building barriers of light, sound, bubbles or electricity on waterways to keep the fish from going upstream in Minnesota waterways.
Although no figures were released in the report, it does say that the cost for these systems is "high." In 2004, the DNR proposed similar solutions that were estimated to cost from $8 million to $25 million.
Even then, the latest report says, the effort would not keep the Asian carp out and it is only a matter of time before the fish populate Minnesota waters.
"Preventing the introduction of Asian carp ... is a daunting challenge," the report said, "and unlikely to be successful in the long-term."
But, the report warns, doing nothing would allow the fish to migrate more quickly into the area and give them more time to destroy the eco-system of the state's lakes and rivers.
Bighead carp, one of the Asian varieties, can grow to 100 pounds and are so voracious they leave nothing for native species. Another variety, the silver carp, is a safety hazard because it leaps out of the water as boats pass.
One of the voracious plankton-eating fish was caught in the St. Croix River in 1994 and another in Lake Pepin in 2004 in southeastern Minnesota. Then last month a commercial fisherman caught a 29-pounder in Lake Pepin.
The sighting unsettled DNR officials because Asian carp usually don't come this far north.
The fish are common in places such as Illinois, Missouri, Iowa and the southern United States. But they have not been spotted in Minnesota for nearly three years.
So the DNR is proposing a number of steps to flog these fish. Apart from the barriers, the agency is proposing: tightening restrictions on importing carp; more vigilance on individuals releasing carp into local waters; and investigating whether these Asian carp are sold in local ethnic stores.
"Delaying the introduction," the report said, "would allow the state to consider alternative management strategies."