Scientists are considering a captive breeding program to ensure the survival of an enigmatic little sea floor walking fish found only in Hobart's Derwent estuary.
Once widespread globally, the finger-sized spotted handfish is now confined to the Tasmanian waterway and may need an insurance population after recent surveys found its numbers were at dangerously low levels.
CSIRO senior research scientist Tim Lynch says the first complete survey of handfish colonies, an exhaustive run of 100 transects this winter in bone-chilling Derwent waters, found a total of just 79 fish.
"It would be very prudent to think about captive breeding of the fish at this stage," said Dr Lynch. "We're organising a workshop to cost it out, and see what we can do."
The frown-faced fish uses its hand-like fins to creep over the sea floor before pouncing on its minute prey. When threatened, it spreads the fins in display.
Listed as critically endangered by the International Union for Conservation of Nature, the handfish may be falling victim to its own habits of careful parental care, and loyalty to local habitat.
Dr Lynch said that unlike many fish which broadcast their eggs into the ocean, the handfish laid them onto the sea floor and then stood guard. But the feral north pacific seastar is demolishing its camouflaging habitat, leaving the handfish exposed to predators.
"We've been laying out small pieces of artificial spawning habitat that is inedible to the starfish, but this gradually gets submerged in the sand," he said.
Local environmental changes also to appeared to be hitting the fish. The survey checked nine previously known handfish colonies and found some in all locations. But in three, local environmental changes appeared to have overwhelmed the fish.
In one place an algal mat had formed on the sea floor from nutrient run-off. In another, yacht moorings had been laid, and at the third, council stormwater drain engineering had broken up the area.
"We found only between one and three fish in each of those places."
Despite its appeal, Dr Lynch said the hardships endured on the survey by the team meant it was unlikely the handfish would attract dive tourists.
"You have to be quite hardy," he said. "These are icy dives, the fish are tucked away behind sponges or in holes, and very difficult to see."
