The disappearing fish delicacy

Originally published by Northern News, Kaikohe on 13 March 2019.

Until the 1960s, toheroa was New Zealand's "great contribution to the epicurean world".

The kai moana was "highly esteemed by the most fastidious gourmet" and a "gift of nature ...

that has done much to advertise the Dominion all over the world", according to the NZ Railways Magazine in 1936.

Toheroa thrived on the western beaches of the North Island Ninety Mile, Ripiro and Muriwai. It abounded on the beaches of Kapiti-Horowhenua near Wellington. Mysteriously, it thrived on Oreti and Te Waewae beaches in Southland.

There were pockets elsewhere.

The surf clam was a staple of the Maori diet for centuries. In the 20th century, it seemed to be an "almost inexhaustible resource" to many.

From 1928-69, Northland factories canned about 20 tonnes of toheroa a year. In 1940, they canned 77 tonnes, the record.

Recreational fishers were just as hungry. In 1966, it's thought 12,000 cars and 50,000 people visited Ripiro beach and harvested about 1 million toheroa - in one weekend.

And then the fishery collapsed. Commercial canning was banned in 1969. Regional closures were staggered and the last legal recreational catch occurred in 1979. All that's left is a supposedly "limited" harvest for customary purposes - meaning by Maori but not exclusively - and poaching.

When the bans were imposed, it was hoped the New Zealand native would recover on it's own.

Stop the harvests and toheroa would come back.

But it's been 40-45 years and toheroa has not come back.

Despite being New Zealand's most protected shellfish, numbers have largely collapsed on Ninety Mile, Muriwai and Kapiti beaches. Ripiro is hanging on.

Only Southland's animal numbers are remotely positive.

What's going on?

In late 2015, Dr Phil Ross, a marine ecologist at the University of Waikato, and colleagues got a big Marsden Fund grant and other money to find out.

"It's the great mystery of New Zealand marine ecology," he said.

Their research is now getting published and the reading is grim. "Illegal harvesting of toheroa is widespread and frequent," they report. The customary take is probably out of control in some places.

Driving vehicles on beaches crush the beach clams or exposes them to predators and killing heat.

Other factors probably include pollution, a lack of fresh water coming onto beaches from inland, and gas bubble disease something like the bends in scuba divers.

Toheroa, in other words, largely haven't been left alone to recover.

In almost all discussions of the customary harvests of toheroa, words such as "limited" and "restricted" are used to indicate these are minor events.

But there's evidence and testimony that customary catches of toheroa are neither.

"Based on our observations ...

Illegal harvesting is common," wrote Ross and co-authors in the main paper on toheroa to come out of the Marsden funding.

Customary harvests are designed for special occasions such as hui and tangi. The Ministry for Primary Industries issues iwi with the power to issue permits and they in turn identify a kaitiaki (custodian, guardian) to issue permits and place rahui (restrictions) on beaches if needed.

New Zealand courts have prosecuted nine poachers for improperly taking more than 50 toheroa and 44 infringement notices have been issued for taking fewer than 50 clams over the past five years, according to the ministry.

Ross insists all is not lost.

Toheroa, Paphies ventricosa, is a broadcast spawner. A single adult female can spawn 15 million to 20 million eggs in one go. If conditions are right, huge numbers of junior toheroa can survive and grow.

In Northland, this happens but the clams disappear before maturing, he said. It's not clear why.

Ross and many others want the species to recover, to make occasional feeds on the beach possible again. Some dream of a renewed commercial fishery and even aquaculture.

None of that will happen without co-operation from iwi, marae, kaitiaki and individuals.

Ross wants to align western science with Matauranga Maori, or traditional knowledge in all its subtlety held by Maori.

The 36-page main Marsden paper is largely an attempt at this. The authors compare "our current scientific understanding of toheroa against the knowledge held by local experts [to] provide a comprehensive summary of toheroa-related knowledge".

"Now is an appropriate time."