Game fish follow warm route south

There was a summer spike in strange marine sightings in the South West/Capes region, as fish typically found in the State’s north made their way down via the warming Leeuwin Current.

Spanish mackerel, marlin and redthroat emporer were just a handful of fish species recently spotted along the South West coast, all of which generally favour the warmer northern waters.

Naturaliste Game and Sport Fishing Club president Graham Morris confirmed a series of uncommon catches in recent months, including a Spanish mackerel bagged by a Japanese tourist off the Busselton jetty.

“There’s been some yellow fin tuna and we’ve seen a lot of baldchin groper in the last few months,” he said.

“As a kid I caught one of those down here, which was a total rarity then, but it seems to be a lot more commonplace now.”

Mr Morris attributed the strange movements of marine species to fluctuations in the Leeuwin Current — a warm water passage which moves south from the North West Cape, around Cape Leeuwin and in some years can influence as far as Tasmania.

Sea temperatures all around the world are on the rise, but Department of Fisheries principal research scientist Gary Jackson said the Leeuwin Current in particular was known as a “warming hotspot” and acted as a “warm water highway” for certain marine species.

“The south western coast is recognised internationally as a part of the ocean that is warming up, on average, more quickly,” he said.

“A lot of the large fish that are highly mobile — mackerel, marlin, whale sharks, other large sharks — will move around, seeking the ocean conditions that suit them.”

Mr Morris said uncommon sightings had been on the rise for several years, such as Spanish mackerel off Augusta, mud crabs in Toby’s inlet and marlin down as far as Albany.

But Dr Jackson said just because a species was spotted in one year, did not necessarily mean it would return in the next.

“Some years the current flows more strongly than others and is linked to El Nino and La Nina cycles,” he said.

“We’ve actually got a slightly weaker period of Leeuwin current at the moment.”

From an environmental perspective, Dr Jackson said the Department of Fisheries was limited in what it could do about warming sea temperatures, but abnormal marine migrations were being monitored closely through the department’s Redmap program — a collaborative online database built on submitted information.

“We certainly have to be mindful and respond and hopefully collect information so we can inform policymakers,” he said.

If you see something unusual in the ocean, report it at www.redmap.org.au .