Leatherjacket swarms abnormal and destructive: photos, video

Seals on a leatherjacket bait ball

A PLAGUE of leatherjackets continues to swarm in waters off Narooma and Bermagui, making life hard for commercial and recreational fishers and having an untold impact on the marine environment.

The phenomenon appears to be something new with fishers not seeing them in such numbers in local waters ever before.

The seals of Montague Island do appear to be taking advantage of these abundant fish with Narooma News editor Stan Gorton filming the marine mammals feeding on schools of small specimens of one particular species on the weekend.

After some research, the leatherjackets in the footage have been identified as threadfin leatherjackets.

The other species showing up in fish traps and on the end of fishing lines are the Chinaman or ocean leatherjackets.

According to commercial fishermen who make their living on the sea, the leatherjacket phenomenon is something new to local waters.

Naroomaís Des Creighton, 87, and his family have fished waters around Montague Island for at least 50 years.

He said he never saw leatherjackets in any numbers in his younger days and they have only showed up in the last few years.

When he was a teenager, he does remember leatherjackets being caught commercially off Sydney, but then ìthey cleaned them out and went broke.î

Bermagui trap and line fisherman Jason Moyce also recalls leatherjackets being caught on a commercial scale off Sydney back in the 1980s and 90s.

But it was only 2000 or 2001 when they started showing up in huge numbers off Sydney in his fish traps.

And since moving to Bermagui, the leatherjackets appear to have followed him down, filling his traps and making the fishing miserable in the last couple of years.

Only on Monday, Jason posted on his Facebook another photo of one of his traps chock full of Chinaman and other oceanic leatherjackets.

“I'm trying my best to rid them. Mission impossible!” he joked.

Moyce said the explosion of different kinds of leatherjacket must be having an impact on the marine environment as they have been known to pick reefs clean.

“There were reefs known for long-fin orange perch but once the jackets showed up these and other fish just disappeared,” he said.

There was a bit of a mystery as to the identity the leatherjackets in the seal feeding footage, with game fishermen referring to them as triggerfish.

But fish expert Mark McGrouther, who is the fish collection manager at the Australian Museum in Sydney, helped identify them as threadfin leatherjackets – Paramonacanthus filicauda.

More can be read about this species on the Australian Museum’s website at http://australianmuseum.net.au/Threadfin-Leatherjacket-Paramonacanthus-filicauda/

According to the website, the species is found in Australia and Papua New Guinea. In Australia it is known from the north-western coast of Western Australia, around the tropical north of the country and south to Tasmania.

McGrouther said thousands of juvenile threadfin leatherjackets washed up on New South Wales beaches in May and June 2004, and mass kills of this species have been recorded in New South Wales and Queensland in previous years.

What was going in Far South Coast waters would however remain a mystery without more scientific research.

There was increasing anecdotal evidence of northern species moving south with blue groper showing up on the north coast of Tasmania.

There is the Redmap (Range Extension Database & Mapping) project that is invites the Australian community to spot, log and map marine species that are uncommon in Australia, or along particular parts of our coast.

Anyone can report unusual phenomenon such as the leatherjackets to the website at www.redmap.org.au

In another twist to this fishy tail, another recent invader is the amberjack, a relative of favourite local fishing target the kingfish.

An amberjack was caught at Montague Island several weeks ago and then during the Narooma Flathead Classic two more were caught by two different teams on one day, one measuring 40cm and other 36cm.

More recently recreational angler Ian Jamieson caught another amberjack on the Clyde River last week.

Again, we turned to Mark McGrouther at the Australian Museum, who identified Ian’s fish as either the regular amberjack (Seriola dumerili) or the high-fin amberjack or almaco jack (Seriola rivoliana) – both relatives of much more locally common kingfish.

Both species are normally more home in tropical waters although the almaco jack has been known to frequent the South Coast.

Still, legendary fishing guide Stuart Hindson who has fished local waters for more than 30 years has never seen amberjack of any kind in the local estuaries or rivers.

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