Devil in the sea of ​​a deep blue a rare sight

Marine biologists from the University of Wollongong (UOW) recorded the first verifiable record of a rare and protected fish in the water, almost twice as deep as it is thought to inhabit, and two kilometers further on the continental shelf.

The discovery of eastern blue devil fish (Paraplesiops bleekeri) well outside its range raises questions about how certain fish species respond to climate change and the need for scientists to work more closely with fishers and fishers. Scientists write what we know about the fish that inhabit the deepwater reefs.

The eastern blue devil fish are rare and endemic to the coastal reefs of eastern Australia. Their bright colors and relatively small size (adults reach 40 centimeters long) make them attractive to the aquarium industry and, as such, they are protected by the New Fisheries Laws. South Wales.

Using video cameras on the ocean floor with attached baits – devices called baited Remote Underwater Video Stations (BRUVS) – researchers from Sydney University, UNSW and NSW's Primary Industries Department have pu diving and in all weather conditions. They have the added benefit of being able to watch for hours without human interference.

Ph.D. Candidate Lachlan Fetterplace, of the UOW School of Biological Sciences, said this rare sighting was part of sequences that consisted of "stranded" samples of what was supposed to be a 75-year-old sandy habitat. kilometers of NSW coast between Jervis Bay Bawley Point.

The eastern blue devil fish was spotted at a depth of 51 meters and two kilometers down on the slope of the continental shelf as previously observed; well outside its published range of depths less than 30 meters.

"We dropped the cameras on what they thought was a sandy bottom and found unmapped reefs with overhangs and crevices," Fetterplace said. "Normally, these images would be stored on hard drives and left to collect dust at the back of the lab.

"Perhaps because the seascape was so interesting that we ran through the one-hour video sample, the electric blue, the white stripes and the shy emergence of an eastern blue devil in a crevasse for investigate a baited camera. "

The researchers report in an article recently published in the journal European Journal of Ecology they do not know historical documents in Australian museums or databases of blue devil fish from the east of more than 30 meters.

It is unlikely that commercial fishermen will encounter them because of their protected status and the complex terrain they inhabit, which is avoided for fear of damaging the nets.

A capture confirmed at a depth of 48 meters on a chartered fishing boat from an eastern blue demon was held off Sydney in February 2018 and recreational fishermen reported having accidentally captured blue devils on reefs known to be in the waters. deeper than 40 meters.

"If the range of the eastern blue devil can be corroborated to at least 50 meters and potentially far beyond, this would significantly extend the known habitat of a rare fish." This knowledge can contribute to the chance of success, while also benefiting the management of deeper offshore reefs. "

Mr Fetterplace said that climate – related changes in rangelands have been documented globally and that it is possible for the eastern blue devils and other reef fish to move their area. distribution in both latitude and depth when they are looking for cooler water.

But without deeper sampling of the deeper reefs on the continental shelf, the extent and extent of the deeper populations of Eastern Blue Devil fish and their impact on other reef fish will remain largely unknown.

The paper also extends the depth range of several other species. Samples from 17 other locations were found in large numbers, well beyond their depth of reading, with immaculate damsels, red morwongs, mado, white ears, silver brooms and ribbons crimson.

"The knowledge that fishermen can provide is potentially important to corroborate scientific observations and increase the sampling effort of rare species, and deep-sea research will greatly benefit from collaboration with fishermen and science programs." citizen.

"These observations remind us once again of how little we know about the deeper oceans and the dangers of limiting conservation and management efforts to shallow, coastal and relatively" accessible "well-studied environments.

"Many other reef fish species are probably found on deeper reefs in Australia and in coastal waters around the world, and we just are not looking deep enough yet."

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More information:
Lachlan C. Fetterplace et al. Natural history report. The devil in depth: expand the known habitat of a rare and protected fish, European Journal of Ecology (2018). DOI: 10.2478 / eje-2018-0003