Asian carp could eat well in Lake Michi­gan

Report em­pha­sizes im­por­tance of keep­ing op­por­tunis­tic fish out

Milwaukee Journal Sentinel - - Front Page -

TRA­VERSE CITY, Mich. – Asian carp are likely to find enough food to spread far­ther if they es­tab­lish breed­ing pop­u­la­tions in Lake Michi­gan, re­in­forc­ing the im­por­tance of pre­vent­ing the in­va­sive fish from gain­ing a foothold, sci­en­tists said in a pa­per re­leased Mon­day.

A study led by Univer­sity of Michi­gan re­searchers found that de­spite a drop-off in plank­ton, the tiny plants and an­i­mals on which big­head and sil­ver carp typ­i­cally feed, the lake has enough di­etary op­tions to sus­tain in­di­vid­ual fish that ven­ture away from nu­tri­ent-rich shore­line ar­eas where most would con­gre­gate.

That im­proves their prospects for col­o­niz­ing large sec­tions of Lake Michi­gan and even­tu­ally spread­ing to the other Great Lakes, said Peter Al­sip, an eco­log­i­cal mod­el­ing data an­a­lyst and lead author of the pa­per pub­lished in the jour­nal Fresh­wa­ter Bi­ol­ogy.

“Our study in­di­cates that the carp can sur­vive and grow in much larger ar­eas of the lake than pre­vi­ous stud­ies sug­gested,” Al­sip said.

Asian carp were im­ported in the late 1960s to gob­ble up al­gae in Deep South sewage la­goons and fish farms. They es­caped into the Mis­sis­sippi River and have mi­grated north­ward, branch­ing into dozens of trib­u­taries.

Pro­lific breed­ers and vo­ra­cious eaters, the in­vaders com­pete with na­tive fish for food and habi­tat. They have be­come the pri­mary fish species in the Illi­nois River, which forms part of an aquatic path­way that leads to Lake Michi­gan through a Chicago-area net­work of rivers and canals.

Au­thor­i­ties have long de­bated how to keep them out of the Great Lakes, where fishing is a $7 bil­lion in­dus­try. The U.S. Army Corps of Engi­neers this year pro­posed equip­ping the Bran­don Road Lock and Dam near Joliet, Illi­nois, with noise­mak­ers, electric bar­ri­ers

and other de­ter­rents at a cost of at least $778 mil­lion.

Some ex­perts have ques­tioned whether the carp would ven­ture from shal­low bays and wet­land ar­eas into the lake’s deeper wa­ters, where filter-feed­ing ze­bra and quagga mus­sels have coated the bot­tom and con­sumed huge vol­umes of plank­ton and nu­tri­ents such as phos­pho­rus.

But the Univer­sity of Michi­gan team said ear­lier stud­ies un­der­es­ti­mated the carps’ di­etary flex­i­bil­ity. They have shown a will­ing­ness to feed on other or­ganic ma­te­rial drift­ing in the wa­ter col­umn — in­clud­ing ex­cre­ment from the mus­sels, Al­sip said.

He and his col­leagues mod­eled lev­els of food availabili­ty and wa­ter tem­per­a­tures to es­ti­mate the well­be­ing of big­head and sil­ver carp when eat­ing mix­tures of plank­ton and non-liv­ing or­ganic ma­te­rial, or “de­tri­tus,” at differ­ent depths.

They con­cluded that the lake, with its aver­age depth of 280 feet, has enough of the mus­sels’ fe­cal pel­lets to keep the carp from starv­ing and even en­able them to grow while seek­ing other fer­tile ter­ri­tory, such as Wis­con­sin’s Green Bay, Al­sip said.

“It definitely in­creases their chance of sur­viv­ing the jour­ney,” he said.

Kevin Irons, aquatic nui­sance species pro­gram direc­tor with the Illi­nois De­part­ment of Nat­u­ral Re­sources, said Lake Michi­gan’s cold tem­per­a­tures, depths and lack of food would pose chal­lenges for the carp. But the Michi­gan study un­der­scores their har­di­ness and adapt­abil­ity, he said.

“They can fast for long pe­ri­ods of time and travel long dis­tances quickly,” Irons said.

“This re­in­forces the im­por­tance of in­vest­ing in pre­ven­tion. Pre­vent­ing them from get­ting in is go­ing to be a lot more effec­tive than con­trol­ling them af­ter they get in.”

Demo­cratic Sen. Gary Peters and Repub­li­can Rep. Bill Huizenga, both from Michi­gan, said the study ramps up pres­sure on Congress to fund pro­grams that pro­tect the lakes from the carp.

“We are on the verge of an un­stop­pable cri­sis for the Great Lakes re­gion, and now is our best chance to stop th­ese ag­gres­sive fish from crash­ing our econ­omy and en­vi­ron­ment,” said Molly Flana­gan, vice president of the Al­liance for the Great Lakes, an ad­vo­cacy group that fa­vors the Bran­don Road Lock and Dam up­grade.

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