Study links Asian carp with Mis­sis­sippi River fish drop

Antelope Valley Press (Sunday) - - Second Front - By JOHN FLESHER AP En­vi­ron­men­tal Writer

TRAVERSE CITY, Mich. — Sport fish have de­clined sig­nif­i­cantly in por­tions of the Up­per Mis­sis­sippi River in­fested with Asian carp, adding ev­i­dence to fears about the in­vader’s threat to na­tive species, ac­cord­ing to a new study.

Analysis of nearly 20 years of pop­u­la­tion data sug­gests the carp are out-com­pet­ing fish prized by an­glers, such as yel­low perch, bluegill, and black and white crap­pie, the re­port said.

Sci­en­tists have long sus­pected Asian carp of starv­ing out other fish in the Mis­sis­sippi and many of its trib­u­taries. The peer-re­viewed study this month in the jour­nal Bi­o­log­i­cal In­va­sions is among the first to es­tab­lish a solid link, lead au­thor John Chick said in an in­ter­view Fri­day.

“The alarms have been out there for a long time now,” said Chick, a fish­eries bi­ol­o­gist who di­rects a Univer­sity of Illi­nois field sta­tion in Al­ton, Illi­nois. “This adds fur­ther mus­tard to the ar­gu­ment that we need to be tak­ing these things se­ri­ously. The trends that have been estab­lished here are not the trends we want to see in other places.”

Four va­ri­eties of Asian carp were im­ported in the late 1960s and early 1970s to clear al­gae and weeds from sewage ponds and fish farms. They es­caped into the Mis­sis­sippi and have mi­grated north­ward.

Big­head and sil­ver carp are the most trou­ble­some. They gorge on tiny an­i­mals and plants known as plank­ton, which vir­tu­ally all fish eat as ju­ve­niles. For some fil­ter-feed­ing species, it’s a life­long sta­ple.

Fed­eral and state agen­cies have spent heav­ily on re­search and tech­nol­ogy to keep them out of key wa­ter­ways.

In their pa­per, Chick and col­leagues there’s rarely enough data to doc­u­ment how in­va­sive species harm na­tives.

But the U.S. Army Corps of En­gi­neers has been mon­i­tor­ing fish in the Up­per Mis­sis­sippi sys­tem for more than two decades, in­clud­ing sev­eral years be­fore the carp ar­rived, us­ing elec­trofish­ing to col­lect sam­ples.

An­a­lyz­ing Corps num­bers com­piled be­tween 1994 and 2013, Chick’s team found sport fish dropped about 30 per­cent in two carp-in­fested ar­eas on the Mis­sis­sippi River and one on the Illi­nois River.

Mean­while, sport fish num­bers grew nearly 35 per­cent in three sec­tions of the Mis­sis­sippi far­ther up­stream that the carp hadn’t reached.

The trends have con­tin­ued, said Chick, who still mon­i­tors Corps data.

The study fo­cused on sil­ver carp, no­to­ri­ous for leap­ing from the wa­ter when star­tled, be­cause they’re more abun­dant in the Up­per Mis­sis­sippi than big­head carp.

It found that sport fish prob­a­bly are los­ing out dur­ing early life stages, when they’re de­pen­dent on plank­ton the carp are gob­bling up.

The re­searchers con­sid­ered other fac­tors in­clud­ing flood­ing, wa­ter tem­per­a­tures and sed­i­ment pol­lu­tion. But none was found to have played a sig­nif­i­cant role in the sport fish trends in the up­per Mis­sis­sippi.

The re­gion has drawn less at­ten­tion in the carp bat­tle than the Great Lakes, re­searchers said, but its out­door recre­ation econ­omy is val­ued at about $2.2 bil­lion.

The study is valu­able be­cause it’s based on di­rect ob­ser­va­tion of fish pop­u­la­tions over an ex­tended pe­riod, said Tammy New­comb, a fish­eries bi­ol­o­gist and Asian carp ex­pert with the Michi­gan De­part­ment of Nat­u­ral Re­sources.

“It’s an­other piece of science that con­trib­utes to the over­all sense of ur­gency” to stop the carps’ ad­vance, said New­comb, who was not part of the study.

Kevin Irons, aquatic nui­sance species man­ager with the Illi­nois De­part­ment of Nat­u­ral Re­sources, who also didn’t take part in the study, said he gen­er­ally agreed with its find­ings.

But he said it didn’t prove in­va­sive carp had caused the sport fish drop-offs and that dif­fer­ences be­tween river sec­tions such as veg­e­ta­tion also can af­fect fish num­bers.

As­so­ci­ated Press

In this June 13, 2012, file photo, Asian carp, jolted by an elec­tric cur­rent from a re­search boat, jump from the Illi­nois River near Ha­vana, Ill.

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