Toolondo threat from in­fes­ta­tion

The Weekly Advertiser Horsham - - News - BY DEAN LAW­SON

Toolondo Reser­voir south of Horsham looms as a po­ten­tial test wa­ter for the re­lease of a carp-spe­cific virus, with re­search re­veal­ing it has a grow­ing in­fes­ta­tion of the pest species.

Catch­ment author­ity leader David Bren­nan said ‘dis­ap­point­ing’ wa­ter sam­ples had re­vealed the lake’s carp pop­u­la­tion had spread across the lake and would now be dif­fi­cult to con­trol.

“EDNA sam­pling re­sults have shown the carp are not sim­ply con­gre­gat­ing in iso­lated ar­eas where we might have been able to tar­get them with elec­tro-fish­ing,” he said.

“The ev­i­dence we’ve re­ceived is that they are wide­spread.”

Mr Bren­nan added the fear now was the carp would be­come the dom­i­nant fish and largest biomass in the lake and the pro­posed re­lease of a virus, de­pend­ing on safety checks, might be timely.

“It’s very dis­ap­point­ing. It has clearly iden­ti­fied that carp have heav­ily in­fil­trated the lake and as a pri­mary recre­ational wa­ter with sig­nif­i­cant his­tor­i­cal and en­vi­ron­men­tal value it might be an ideal tar­get for a virus re­lease,” he said.

“In other words, it might be a case of ‘the sooner we get the carp virus the bet­ter’.

“We’re talk­ing about a high-po­ten­tial lake – one of the best fish­ing and sight­see­ing lakes in Vic­to­ria that hasn’t had a lengthy his­tory of carp in­va­sion.

“Who knows? We might be able to stop it in its tracks.”

Wim­mera Catch­ment Man­age­ment Author­ity col­lected nine sam­ples from Toolondo’s three pri­mary wet­lands for EDNA anal­y­sis in re­sponse to re­ports of grow­ing carp catches from the lake.

EDNA tech­nol­ogy in­volves iden­ti­fy­ing cells present in wa­ter sam­ples to as­sess lev­els and types of aquatic life in a water­way.

Mr Bren­nan said the re­search had shown the lake had a range of carp age groups.

“The in­di­ca­tions are the carp have been in there a while,” he said.

“There are fish in there weigh­ing up to 10 pounds to fish that have only bred in the past 12 to 18 months.

“En­vi­ron­men­tal con­di­tions, with Toolondo be­ing a large lake with shal­low ar­eas, are also suit­able for the pop­u­la­tion to sig­nif­i­cantly in­crease.

“We’re in dis­cus­sions with Fish­eries Vic­to­ria about what op­tions and tech­niques that could be de­ployed to help con­trol the carp, but this won’t be any easy fix. As it stands now, elec­tro-fish­ing would not be an ef­fec­tive con­trol method.”

The catch­ment man­age­ment author­ity has sug­gested the Wim­mera River sys­tem, that in­cludes Toolondo, might be ideal as a virus-re­lease site as part of a Na­tional Carp Con­trol Plan.

The fu­ture of Toolondo Reser­voir, with a rep­u­ta­tion as one of the best tro­phy-trout fish­ing lakes in Aus­tralia, has been the sub­ject of con­sid­er­able de­bate.

The State Gov­ern­ment has been di­rectly in­volved in projects to pro­tect its sus­tain­abil­ity as a recre­ational fish­ery.

Wa­ter has been flow­ing into Toolondo from Rock­lands Reser­voir as part of a wa­ter-man­age­ment sched­ule.

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