CRAYS ARE BACK

The Riverine Herald - - FRONT PAGE - By Lach­lan Durl­ing

IT’S been more than a decade since Mur­ray cray­fish were seen in vi­able num­bers – but that’s about to change.

Re­searchers have started re­pop­u­lat­ing the lo­cal area in what they are hop­ing will be the rst stage in the re­cov­ery of the crus­tacean’s num­bers.

THE Mur­ray cray­fish is back.

Not in big num­bers yet but re­searchers have made a trial in­tro­duc­tion of 200 crays to see how they cope after the mil­len­nium drought and floods dev­as­tated lo­cal num­bers.

The crays were qui­etly re­leased in July and Na­ture Glenelg Trust re­searcher Nick Whiterod said it was look­ing good as the crays have shown a high sur­vival rate in the river.

“We’re rein­tro­duc­ing them back into a stretch of wa­ter that was im­pacted by a sig­nif­i­cant black wa­ter event, and the pop­u­la­tion just hadn’t re­ally been bounc­ing back at all,” he said.

“The black wa­ter event lasted for about six months in cer­tain ar­eas, and it af­fected an 1800km stretch along the Mur­ray.

“Our most re­cent sam­ple was last Friday and we de­tected the species, so it’s good to see that they’re hang­ing around.

“There have been a few pock­ets in and around Echuca, up­stream to­wards Co­huna as well, but noth­ing like what the num­bers were be­fore­hand.

‘‘Once the flood­ing came a lot of the flood­plain ar­eas went un­der and some of those hadn’t been in­un­dated for as many as 20 years,’’ Dr Whiterod said.

‘‘Leaf lit­ter that had been build­ing up on the bank had ac­cu­mu­lated and then when those big floods oc­curred, mi­crobes started break­ing down the leaf lit­ter and strip­ping oxy­gen from the wa­ter.

‘‘Essen­tially that’s what black wa­ter is all about — it’s wa­ter that comes off the flood plain [with] low oxy­gen lev­els or con­cen­tra­tions and it comes back into the main chan­nel and low­ers the oxy­gen concentration.’’

While Dr Whiterod was con­fi­dent the rein­tro­duc­tions would bring pop­u­la­tion num­bers up, he said this was only the be­gin­ning for the con­ser­va­tion ef­forts.

“We placed about 200 back in the river, but we feel that it wasn’t enough so that’s why we’ve planned to do it again,” he said

“Fish­eries closed off the sec­tion down­stream from Tocumwal about five years ago, and it’s not likely to open back up, sim­ply be­cause the pop­u­la­tion hasn’t been able to get back to the pre­vi­ous num­bers.”

“A ma­jor prob­lem is that they’re slow grow­ing and long liv­ing, so they’re not re­ally in a rush breed­ing wise, and that can af­fect our re­pop­u­la­tion pro­grams too as we can’t make too much of an im­pact on the pop­u­la­tion where we’re get­ting them from.”

While it could be ar­gued there have been at­tempts at rein­tro­duc­tions be­fore, this is the only of­fi­cial one.

“The translo­ca­tion we’re do­ing is in ad­di­tion to some other pro­grams but some­thing like this hasn’t been done in al­most a cen­tury, not of­fi­cially any­way,” he said.

“There have been some peo­ple try­ing to do it them­selves, but gen­er­ally the ge­netic di­ver­sity is un­known and there needs to be a pretty size­able pop­u­la­tion to make sure they sur­vive. The re­search we’ve done gives the best chance at suc­cess.”

CLAW­ING THEIR WAY BACK: Two of the Mur­ray Cray­fish re­leased near Echuca-Moama as part of a ma­jor re­stock­ing trial.

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