Rare fish spotted for first time in 27 years

Marine surveyors from the CSIRO have spotted a rare handfish species in the Bass Strait last seen nearly 30 years ago.

The narrowbody handfish (Pezichthys compressus) is a mysterious and rarely sighted species patrolling the seabed off Victoria’s southeast coast. It was first discovered in 1986 and was last seen in 1996.

That was about the time the last survey of ecosystems in the region was conducted.

Enlarged image of pezichthys compressus taken from the rv investigator's deep tow camera.
Enlarged image of Pezichthys compressus taken from the RV Investigator’s deep tow camera. Credit: Supplied.

In July, the CSIRO performed a 33-day survey of the region for the first time in 25 years. Aboard the RV Investigator, the South-East Australian Marine Ecosystem Survey (SEA-MES) undertook the same inspections of these ecosystems as its preceding missions a quarter of a century ago. In doing so, the teams, led by CSIRO research group leader Dr Rich Little, hope to understand shifts in these environments over three decades.

“Anecdotal evidence that’s coming mainly from fisheries, but other areas as well, is that the ecosystem is changed for some reason or other,” Little tells Cosmos. “We don’t know whether it’s fisheries management or whether it’s climate.”

To understand ecosystem shifts, SEA-MES employs the same techniques used in the nineties, such as using drag nets along the ocean’s benthic zone – the deepest part of a water region – and through higher levels of the water column to take species samples.

Surely analysis techniques have moved on from net dragging in the last 30 years? That is true, but by using archaic methods like these, the researchers are able to effectively compare apples with apples.

Concurrently, they used modern techniques to take water samples at depths of about 500 metres. As well as analysing water chemistry, traces of DNA will be scrutinised to determine the makeup of life within these regions.

Csiro record of a pezichthys compressus
CSIRO record of a Pezichthys compressus. Credit: Supplied.

Performing both trawling and water sampling for side-by-side data comparisons now should mean, eventually, researchers can do away with destructive net-based sampling, a goal of the Australian Government’s parks management agency.

“The trawling [and] the netting that we do, is actually quite disruptive, we’re really doing some damage to the bottom,” says Little.

“Environmental DNA is non-extractive, and so it’s non-destructive.

“Parks Australia is really interested in moving from extractive sampling, where we’re actually harming the marine parks that were set up to do the conservation, to the non-extractive sampling, which is using the DNA techniques.”

At night, nets are kept in storage as a video camera is lowered into the water and dragged along the ocean floor. This allows the spotting of benthic species, particularly rare organisms like the narrowbody handfish. eDNA samples are also taken to help identify species potentially hidden from the camera.

“There’s a lot of cryptic species… there’s species hidden in the mud, you don’t see a lot of stuff,” says Little.

“A lot of the species are afraid of the [camera] lights, so they scatter. It’s really interesting to see what DNA we are seeing in the water and what we are actually seeing on the video.”

Updating ecosystem health for marine park performance

More than 430 million hectares of Australian ocean – that’s about half the continent’s land area and equivalent to 48% of territorial waters – are protected marine parks. These are intended to help conserve species as well as provide opportunities for economic activity through tourism and fishing industries. Increasingly, Australian waters are being considered for the installation of renewable wind turbines.

Surveys like SEA-MES are important checks on the health of marine parks whether through monitoring environmental responses to human disturbances or broader climate change impacts.

And in some regions, human impacts on ecosystems are obvious. At 400-500 metres beneath the surface, SEA-MES researchers see objects like old fishing rods and lines, and milk crates. Even submarine listening devices were hauled from the deep.

Benthic zone image from the bass strait taken by the rv investigator’s deep tow camera.
Benthic zone image from the Bass Strait taken by the RV Investigator’s deep tow camera. Credit: Supplied.

Being able to record human impacts can support benchmarking for regulators, as well as for parties seeking to begin activity in the region. That could be a commercial fisher, or an energy company seeking build approvals.

“We saw a whole range of things… if you actually have a look down there, our impacts are quite stark,” Little says.

“There’s all sorts of activity out there, that whole area is just so congested with economic value, with non-market value in terms of the biodiversity, the recreational and the commercial fisheries. It’s really a contested space.

“These surveys are really just showing what the system is currently like, before it actually gets busier.”

SEA-MES is scheduled to return to waters off south-east Australia in May 2024.

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