Diver discovery doubles numbers of rare walking fish

archive – Diving NewsDiver discovery doubles numbers of rare walking fish

A team of divers in Australia have discovered a new population of what is believed to be the world's rarest fish.

Red handfish (Thymichthys politus), which are notable for walking on the seabed rather than swimming, are found only off south-east Tasmania, but until now only a single population of 20-40 individuals had been identified.

The new colony was confirmed by seven divers from the University of Tasmania’s Institute for Marine & Antarctic Studies (IMAS) and the citizen-science project Reef Life Survey (RLS), following up on a reported sighting of a single fish by a member of the public.

The new site, at an undisclosed location, contains a similar number of fish to the previously known population in Frederick Henry Bay, some distance away. Both sites measure only about 50 by 20m, because the fishes’ range is limited by their method of getting around.

IMAS Technical Officer Antonia Cooper spotted the first handfish just as the team was about to give up after two days of searching.

“We were diving for approximately three and a half hours, and at about the two-hour mark we were all looking at each other thinking this is not looking promising,” said Cooper.

“My dive partner went to tell the other divers that we were going to start heading in, and I was half-heartedly flicking algae around when, lo and behold, I found a red handfish.

“Finding a new population that is definitely distinct from the existing one is very exciting. It means there’s potentially a bigger gene-pool, and also that there are potentially other populations out there that we’ve yet to find.”

IMAS scientist Dr Rick Stuart-Smith, who co-founded Reef Life Survey in 2007, described the discovery of the fish as “a huge relief, as it effectively doubles how many we think are left on the planet. We’ve already learned a lot from finding this second population because their habitat isn’t identical to that of the first population, so we can take some heart from knowing red handfish are not as critically dependent on that particular set of local conditions.”

Another species, the spotted handfish, is still observed in Tasmania, but a third, Ziebell’s handfish, is listed as endangered and feared possibly extinct. IMAS and RLS will work with the government, which helps to fund their work, to manage the red handfish sites.

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