Divers in Tasmania have discovered a new population of red handfish, doubling the known population of the elusive and extremely rare fish and raising hopes that more may be found.

Until last week the remaining population of red handfish, Thymichthys politus, was believed to be confined to one long reef in in south-east Tasmania.

A recent survey at that site found eight individual fish at that site, prompting scientists to estimate the reef housed 20 to 40 handfish.

The second site, discovered on a similarly-sized bit of reef a short distance away, is estimated to house the same number of fish.

It was discovered after a member of the public reported seeing a red handfish in the area and a team of seven divers spent two days searching the reef.

“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,” diver Antonia Cooper said.

“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.”

You hardly ever see red handfish actually moving ... it’s just a big effort for them

University of Tasmania researcher with the Institute for Marine and Antarctic Studies, Rick Stuart-Smith, said it was possible there were other undiscovered populations.

However, Stuart-Smith, who coordinates the annual survey project, said the new populations were likely to be genetically isolated because red handfish are not built for long swims.

“If they are disturbed they can do a little burst, they will swim 50cm in a burst and then settle again,” he told Guardian Australia. “They waddle on their fins, they are just trudging along the bottom. In fact you hardly ever see them actually moving.

“Imagine something that’s seven or nine centimetres long trying to walk 1km on a rocky ocean bottom … they are sitting ducks, plus it’s just a big effort for them.”

There are three species of critically endangered handfish endemic to Tasmania. The red handfish is the rarest of those still that can still be found in the wild.

Ziebell’s handfish, Brachiopsilus ziebelli, was likely to be extinct, Stuart-Smith said.

A captive breeding program for the spotted handfish, Brachionichthys hirsutus, began in September, and the fish was made the mascot of the Dark Mofo festival.

Stuart-Smith said researchers would review the viability of a captive breeding program for red handfish now that the known wild population was large enough to cope with the capture of a few breeding pairs.