On some of the wild sandy beaches of the West Coast of New Zealand, pounded by the surf rolling in from the Tasman Sea, there live (or rather, used to live) toheroa. Toheroa are a large bivalve mollusc, almost as large as an adult’s hand, that buries itself in the sand along these beaches in a line between high and low water, feeding by filtering algae and other plankton from the upper layers of sand. The contents of their stomachs and guts consequently have a deep green colour. They are also notable for having a long cream-coloured muscular ‘tongue,’ more or less the size and shape of a human tongue, which they use to dig themselves into the sand. The name ‘toheroa’ means ‘long tongue’ in te reo Maori.
Unlike most similar molluscs, which can seem relatively inert at first glance, the toheroa is very active – if you placed one on the surface of the wet sand, you could watch as the tongue came out, and the shellfish rapidly pulled itself down into the sand.
I say this from long memory. For most people in New Zealand, memory is all that is left of living toheroa. People of my age and older can remember gathering toheroa and eating them, usually in the form of a rich green soup. It is a taste you never forget – like nothing else in the world. But for at least the last three or four decades, toheroa have teetered on the brink of extinction, and almost all gathering of them has been forbidden. They live nowhere else in the world.
Earlier this year my 94-year-old mother moved into a rest home, and I have been helping to clear out and sell her house. Among the treasures I found there was a box containing some cans of whole cooked toheroa dating back to the 1950s. It seems almost unbelievable today that toheroa were once so abundant that they were exploited commercially in this way, but I have the proof beside me as I write. According to the label, the cannery was at Tikinui, on the northern shores of the Kaipara Harbour, although the toheroa would have come not from the harbour itself but from the surf beach a short distance over the dunes to the west.
My parents moved to New Zealand from Australia in 1956, not long before I was born, when my father was appointed managing director of ICI in New Zealand (the very frankly-named Imperial Chemical Industries). For some reason, which probably had more to do with the gastronomic preferences of previous managers than with good business practice, the company involved in canning toheroa was a subsidiary of ICI. At any rate, by the time my father took the reins, the toheroa were badly depleted by the operations of the cannery. I have heard it said that they used a mechanical digger to turn over the sand on the beach, with all the additional destruction and waste that that practice entails. Soon the operation was no longer economic, and was shut down. Some of the last remaining cans in stock were given to the lucky managing director, who made good use of them over the subsequent years.
After the end of commercial harvesting (there were two other canning operations that closed around the same time), toheroa remained open for recreational harvest, but as the numbers of shellfish continued to decline throughout the 1960s increasingly steep restrictions were imposed. The brief open seasons became a social occasion, with hundreds of people flocking to the beaches to fill their bags to the legal limit. By about 1970 a total ban was imposed on public harvest, re-opening only for one week in 1977 – this was the last occasion that I tasted freshly-gathered toheroa. Despite the bans on harvesting, the toheroa never returned in sufficient numbers to permit a harvest.
Toheroa had been an important part of the diet of Maori tribes that lived near these West Coast beaches from before the time of European settlement, and Maori conserved the resource carefully. As early as 1850 there were complaints from Maori about Europeans over-exploiting the toheroa.
Te Tiriti o Waitangi, signed in 1840 between Maori and the British Crown, guaranteed Maori use in perpetuity of their forests and fisheries; that clause of the Treaty has been a point of contention right down to the present day. In 2004 the Labour government of the day passed the Foreshore and Seabed Act, taking ownership of the foreshore and seabed to the Crown and effectively overturning customary Maori rights under the Treaty. (The drive to adopt this measure came from the growing development of commercial mussel farming operations, and the fear that Maori might use their Treaty rights to claim a share of them.)
This Act was met with broad opposition from Maori, including a hikoi (march) which culminated in a rally of 20,000 outside Parliament in May 2004. It triggered a crisis in the Labour Party, and in the long-standing tradition of support to the party from Maori. Labour Party junior minister Tariana Turia voted against the legislation and resigned from the Labour Party.
Toheroa did not feature much in these debates, having been off-limits to both commercial and recreational use for so long they had been all but forgotten. But Maori living in the regions where there are toheroa remain their guardians. The shellfish have not entirely disappeared, but their numbers remain at a small fraction of earlier levels, despite some strenuous conservation efforts. Years of work have been done by members of Te Uri o Hau, a Ngati Whatua hapu (sub-tribe) on the northern Kaipara harbour, seeding the toheroa beds with juveniles and planting the dunes further back to create favourable ecological conditions. Toheroa appear to grow best near where fresh water streams pass beneath the sand.
Why have the protections from harvesting and other conservation efforts been so limited in their success? Te Uri o Hau leader Mikaera Miru points to predation of the juveniles by pied oystercatcher as one significant factor setting back conservation work, and has called for culling the birds.
Predation by gulls has also been seen in the past. It is also known that paddle crabs are capable of eating even large adult toheroa by snipping through the shells with their pincers, although mostly the crabs eat large numbers of spat (the larval stage of the shellfish).
All of these predators are indigenous to New Zealand, and so have long coexisted with abundant toheroa prior to human habitation on these islands. However, the relative numbers of the species are very much affected by human activity. Gulls, being opportunistic scavengers as well as predators, tend to increase in number as human populations grow, congregating at rubbish dumps and other places where humans dispose of food or animal waste. Observers in the 1950s noted that the gulls gathered around the commercial toheroa operations and feasted on the shellfish that were exposed and damaged by the diggers, apparently not being able to dig toheroa from the sand themselves. By the mid-1960s the gulls were observed digging small toheroa from undisturbed beds.
But it is the paddle crabs that have been the chief beneficiaries of human activity. There has been a sharp increase in the numbers of paddle crabs since the 1970s, coinciding with expansion of commercial fishing of the paddle crabs’ predators, the large snapper, rig shark and other major commercially-fished species.
(On the reefs and rocky shores, over-fishing of snapper has similarly resulted in super-abundance of another species predated by snapper: the kina, or sea-urchin. A grazing animal, kina in such vast numbers can destroy the kelp forests, leaving the reefs as ‘kina barrens’, unable to support other species. Prominent diver Wade Doak says this is “equivalent to a massive, largely unseen deforestation of our terrestrial wilderness.”)
It is estimated that the snapper stocks in the West Coast commercial region (SNA8) have been reduced to 8% of the original stocks. The snapper fishery is further threatened by a proposal to build 200 gigantic underwater turbines in the Kaipara Harbour, to generate power from tidal motion. The Kaipara Harbour is a major spawning ground for the fish – one study has shown that 98% of the snapper on the North Island West Coast originate from the Kaipara Harbour. Te Uri o Hau is opposed to the turbines.
So the toheroa decline that began with simple over-exploitation of a natural resource by a profit-driven enterprise can not be reversed just by ending the over-exploitation and hoping that the stocks will recover. A complex web of causes and effects is at play, with over-fishing of snapper looming as the central problem.
One immediate measure that could effectively counter the problem is the establishment of further marine reserves on the West Coast. The reserves created on the East Coast have shown beyond all doubt that as soon as all fishing is stopped even in a limited area, the big predators return, the kina are kept under control, and the kelp forests, with all their variety of species, quickly recover. A glance at the map shows that there are no reserves at all on the West Coast from Cape Reinga to Taranaki – the principal range of toheroa. A reserve near the entrance to the Kaipara Harbour could not only afford some protection to the threatened toheroa, but would also be in the long-term interest of snapper fishers, both commercial and recreational.
Ultimately, however, the tendency towards marine environmental degradation can only be prevented by taking management of fisheries out of the hands of competing private enterprises, each driven by market forces to maximise its own share of the resource, even as the resource itself goes into terminal decline.