Crayfish may crawl out of the sea to feed

Wellington's south coast could witness the march of the crayfish, as they swell in numbers and crawl out of the sea to seek new food sources.

New research on Wellington's Taputeranga Marine Reserve has showed the depleted crayfish population will recover from the effects of overfishing, but it could take as long as 40 years.

"We will see bigger crayfish, and we'll see more abundant crayfish," marine biologist professor Jonathan Gardner, of Victoria University, said.

As their population grew, crayfish off the south coast would need to look for different food sources, he said. Blue mussels did not grow in the area naturally, so food sources were limited.

"In Wellington, it means we'll have a change in both diet and behaviour."

It was likely that crayfish would begin to move into the intertidal zone, even crawling out of the ocean at night to feed on seaweed.

"It's mindblowing to think crayfish commonly used to inhabit the intertidal zone. They would crawl into crevices and under rocks."

In the past, Maori caught crayfish by feeling for them with their feet, grabbing them by their antennae and hurling them ashore.

The 854ha Taputeranga reserve was opened in 2008.

"It's only been in effect for six years, Prof Gardner said. "They are starting to come back, but it will take decades to reach the levels they were a couple of generations ago in the 1940s."

There were about four times as many crayfish then as now, the study said.

Prof Gardner said they were "opportunistic scavengers". "They prefer meat, but they'll take what they can get."

They had already been observed in the intertidal zone in the Te Tapuwae o Rongokako Marine Reserve, near Gisborne, created in 1999.

The new study compared past fishing records to the current state of the south coast.

It involved scientists from Victoria University, the University of British Columbia, and Niwa.

The lead author, PhD student Tyler Eddy, collected data over three years of diving in the area.

The Dominion Post