The Elusive Toheroa
Once dug in their thousands by seafood lovers throughout the country, New Zealand’s “national shellfish” has fallen upon hard times lately. Glenys Stace investigates the demise of a delicacy.
On an icy Southland morning, John Rance stepped on to Oreti Beach and began to dig. He had travelled all night from Dunedin to be there. Along with 20,000 other people, he had eleven magic hours in which to find five legal-size toheroa. To shellfish-lovers like John, it was an opportunity too good to miss.
“I’ve dug these things every season for the past thirty years,” he told a local reporter. “They’re the food of kings!”
“They’re worth every freezing toe,” laughed Maureen Knight, of Invercargill.
Saturday, September 8 was the day the Ministry of Agriculture and Fisheries decreed to be the 1990 open season for toheroa at Oreti Beach, one of only a handful of beaches in New Zealand where toheroa can be found. There hadn’t been an open season on Oreti since 1981, and no-one knows when or if there will be another. Some Northland beaches have been closed to toheroa digging for 20 years.
Those who could stand the biting wind and ice-cold water managed to collect their limit before the snowflakes froze their fingers. Other less rugged characters left the beach with one or two, some empty-handed. Five people were taken from the beach suffering from hypothermia. Helicopters patrolled overhead to prevent poachers escaping through the dunes with more than their limit, while fisheries officers checked bags and buckets at beach entrances.
“Last time it hailed like buggery and I said I’d never be back. Here I am, though. Someone’s got to show the grand-kids how to get them. They’ve never had the chance to do it before,” declared Hazel Hedgson, who has not missed a toheroa season for 20 years.
No doubt many Southlanders wondered whether the paltry limit of five toheroa was worth the bother. In the 1920s the daily limit on toheroa was 50 per person, and the shellfish could be taken for ten months of the year. Even in the 1950s there was an open season of two months, and the limit was a respectable 20 per day—and considering the size of the toheroa (up to 140mm long) that was a lot of fritters. These days, however, toheroa are fast becoming a distant, palate-tingling memory.
Like many boom and bust sagas, What causes the enormous fluctuations in numbers of toheroa? Will we see again the free and open seasons that our forebears enjoyed?
The little research that has been done on toheroa indicates that no one factor alone is responsible for this depletion. Climate, changes in land and sea conditions, predation and human interference possibly all play a part.
Toheroa live in the relentless, heaving surf of the west coast. The beaches tend to be extensive and flat, up to 150m from the drift line down to low tide mark, with very fine sand particles. The toheroa beds are found around the mid-tide mark, and in normal conditions that part of the beach is covered and uncovered with each rise and fall of the tide.
Fred West, a digger for the Tikinui factory, explained the structure of the beds: “The biggest toheroa lived furthest down the beach, but never lower than half tide. We would begin to dig at the lower end of the beds and work our way up. We’d move on to the next strip when the toheroa got too small to bother with, and that was quite a lot bigger than legal size. When the beds were really full, the small toheroa would be right over the top of the big ones in layers.”
Toheroa eat and breathe through a system of siphons, which act like snorkels, extending upward through the sand to the surface (see diagram). A stream of water and food particles is sucked down the inhalent siphon, passed across the gills, where oxygen is absorbed and food particles are collected, and channelled back out the exhalent siphon. When the tide recedes, the siphons are withdrawn, leaving two tell-tale holes in the moist sand.
The maximum depth of a shellfish in the sand is determined by the length of its siphons. Mature toheroa have been found at depths of 15cm, and sometimes up to 30cm.
Because toheroa live well above low water mark, there are times when they are barely covered by the incoming tide (for example, when a strong offshore wind is blowing). During such conditions the shellfish run the risk of drying out—a risk which is heightened by the fact that toheroa are unable to completely close their shells.
Following long periods of hot easterly weather, toheroa have been observed to rise to the surface of the beds, and, unless conditions improved, many would die.
It is likely that the early onset of easterly winds in 1938 caused the death of some 20 million toheroa on Ninety Mile Beach, and probably the whole west coast was affected. Alan Webb, a former commercial fisherman at Glinks Gully, recalled the event: “The beach looked like it was covered with patches of snow, dead and dying toheroa everywhere, some still half buried, others washed up on the beach. And the stench! If the wind had changed to a westerly, it could have been smelled for miles inland.” These mass mortalities have been quite common, the last occurring in 1971.
Some toheroa devotees point to the fact that the position of the best beds often coincided with areas of fresh water seepage from lakes behind the sand dunes. This run-off kept the beds moist and cool, they claim, and protected the toheroa from desiccation. While recent research has failed to prove such a correlation, there is no doubt that the reclamation of the dunes through forestry has vastly decreased the amount of fresh water seeping on to the beaches.
Toheroa breed from about October through to February. When conditions are right the females and males (of which there are roughly equal numbers) release their eggs and sperm into the water. The fertilised eggs turn into minute swimming larvae (spat) which live and grow in the plankton for about 20 days before being eventually washed up on the beach as miniature toheroa smaller than a pinhead by incoming tides.
The juveniles grow quickly (up to 65mm in the first year), but growth brings its hazards. During the summer months sea birds gorge themselves on the young shellfish for weeks on end. Black-backed gulls, voracious predators, have been seen eating toheroa all day long, regurgitating the undigested shell and continuing with their feast. Even today, at times the beach runs white when the partially digested shell is gently washed by the first ripples of the incoming tide.
The gulls eat all but the largest toheroa. The small ones they simply crush and swallow, shell and all, but they have also been observed with toheroa as large as 120mm in their beaks, soaring to about 80 metres and dropping the shellfish on the beach over and over until the shell breaks. Oystercatchers also do considerable damage to the beds, thrusting their beaks into sand, twisting open the toheroa’s shell, taking the meat and moving on to the next prey.
Paddle crabs, a more recently arrived predator, take their toll as well. They can dig down and get their sharp pincers into even the largest toheroa, snipping away at the muscles until the shell opens (see “The secret world of crabs,” New Zealand Geographic, Number 8). Their effect is greatest, however, on the tiny, newly settled shellfish, which they consume whole, in their thousands.
Snapper also feed on toheroa. Alan Webb has seen schools of snapper, heads down, tails up, feeding in the surf in large schools. Snapper take whole juvenile toheroa and also bite off the tips of the siphons of adults, killing them.
For those who have never seen it, toheroa soup is green. And here lies another possible reason for the toheroa’s decline.
In winter and early spring, the west coast waters have traditonally been saturated with phytoplankton (green algae such as diatoms and dinoflagellates) blown onshore by the westerly winds and assisted by ocean currents. These phytoplankton blooms appeared as an oily scum on the waves, and as the frothy green edge of each crest pounded on to the sand, a thick, moist deposit several centimetres deep was left on top of the toheroa beds. During such times of phytoplankton abundance the toheroa thrived, their siphons immersed in a nutrient cocktail.
In recent years, the conditions necessary to bring the plankton on shore have been absent. The near-shore currents have been unpredictable and variable, sometimes flowing north along the whole west coast, sometimes diverging below Ninety Mile Beach and flowing south all the way to Cape Egmont. Combined with unseasonal offshore winds this has meant that the phytoplankton bloom has not arrived.
If the toheroa’s decline is being caused by changes in climate and sea currents, one would expect the same to be true for its cousin and neigh-bour the tuatua. In reality, tuatua are on the increase on west coast beaches. Unlike toheroa, their beds are seldom uncovered by the tide, and extend well beyond the breakers, but on occasions the two species have been found in the same bed. This has led to the accusation that tuatua are crowding out the juvenile toheroa, but so little is known about the growth of both species that it is impossible to say for sure that one is increasing at the expense of the other.
Not all hazards the toheroa face are the consequence of their natural environment. Both Maori and Pakeha have taken a great liking to the shellfish, and, alongside pavlova and whitebait fritters, toheroa soup has undoubtedly been one of New Zealand’s great contributions to the epicurean world.
Last century toheroa were a popular item of trade, both live and dried.
But it was not until early this century that toheroa became a national obsession. A story widely circulated reported that the Prince of Wales (later to become Edward VIII) on a visit to New Zealand in 1921 asked for a second helping of the green broth. This staggering break with royal protocol was reported in newspapers all round the Empire, and helped put New Zealand on the map!
After this, no self-respecting New Zealand hotel was without toheroa soup on its menu, and the collecting and eating of toheroa became a national pastime.
The first toheroa cannery was established in the 1890s at Mahuta Gap, on Dargaville Beach, and before long four factories operated on that stretch of coastline. Toheroas were canned at Waipapakauri, Muriwai, the Wellington beaches and Te Waewae for brief periods at various times, and the last cannery closed as recently as 1971.
Was commercial exploitation to blame for the toheroa’s demise? Probably not. In 1940 the Waipapakauri cannery took only one million of an estimated 10.25 million shellfish of legal size on the beach, which hardly suggests that the canning could have had any great effect. Yet two years later there were not enough to can economically. In 1946 there was an amazing return, with estimates up to 10 million again, but in 1949 the factory manager, Reg Rule, could not find one living specimen on the beach. All through the history of the canning operations the toheroa numbers continued to fluctuate wildly reaching numbers as high as 25 million in the early 1960s.
Toheroa have an enormous procreative potential. A single mature female is capable of releasing 20 million eggs in a spawning—and there may be three spawnings in a season. The hazards, of course, are enormous, but they apply to all “broadcast spawning” marine organisms. Many eggs will be washed away before they ever meet a toheroa sperm. Some larvae will not make it back to land, and others will be eaten by filter-feeding animals along the shore and in the open ocean. However, the system guarantees wide distribution of larvae, and, when conditions are right, a huge potential settlement.
Apart from the toheroa’s natural reproductive powers, the shellfish is also capable of shifting itself from one place to another. Whole beds have been observed pulling them‑selves out of the sand and being carried away with the waves. As an incoming wave washes them up the shore, they extend their foot, burrow into the sand and hold on against the backwash. Toheroa can settle, be washed out and resettle dozens of times until they reach a desired spot fin the shore.
The human dimension in the toheroa’s decline doesn’t just relate to taking the shellfish from the beach; there is also the damage caused by vehicles on the beach. During the 1968 two-week open season on Dargaville Beach an estimated 37,000 vehicles were driven over the beds. Today, on some weekends 800-900 off-road vehicles will traverse Muriwai, and in the peak in summer some 35 tourist buses drive along Ninety Mile Beach every day.
As well as crushing juveniles with the sheer weight of the vehicle, car tracks also disturb toheroa buried deeper in the sand. As a vehicle passes overhead, the sand is slightly liquefied, and the shellfish tend to rise towards the surface.
How this affects them is not clear. As with all organisms that live between the tides, life for the toheroa is a precarious balance of many factors such as temperature, moisture, oxygen levels, food availability and living space. For example, an increase in temperature reduces the amount of oxygen available in the water trapped between sand particles, and a decrease in moisture probably has an adverse effect on the toheroa’s burrowing ability.
By drawing toheroa closer to the surface, vehicles may be increasing the animal’s vulnerability to overheating and oxygen starvation, while at the same time making it more difficult for them to burrow away from danger.
Vehicle pressure also causes toheroa to “eject” a jet of water from their mantle cavity, and this may have an effect on their ability to resist desiccation. Retired fisheries officer Don Young described the phenomenon of beds of squirting toheroa as “going through a car wash upside down.”
Poaching, of which the stories are numerous and colourful, has also had an impact. In the days when toheroa were plentiful, a serious poacher could take 1000 shellfish in a night’s work, though there are also tales of poachers with bulldozers ploughing up whole beds, sorting the shellfish at a secret location and fencing them through the local hotels.
Most poaching was less ambitious. Wily inspectors have caught groups of people with the casing of their spare tyre packed with illegal shellfish, and women with their handbags lined with plastic and full of illegal bounty. Children were sometimes encouraged to build sandcastles on toheroa beds, and later bring the spoils to their parents’ baches and caravans in sand-covered kiddy buckets. Cardigan-clad women would go for a walk along the beach and return looking two or three sizes bigger on account of toheroa concealed in internal pockets.
One still hears stories of “late night shopping on Ninety Mile Beach”, and bags of toheroa probably still pass from hand to hand in the pub with a wink and a nod, but the trade is probably declining. For one thing, the fines are hefty and prosecution is automatic if you’re caught. The maximum fine for taking toheroa today is $10,000, plus forfeiture of any property used in commission of the offence, and with the decline in numbers, it’s becoming that much more difficult to make a lucrative haul in the first place.
One of the many puzzles surrounding toheroa is the presence on beaches such as Muriwai of large, heavy toheroa shells bleached white by sun and surf. Some are 150mm in length, and all are substantially thicker than modern toheroa shells. Similar shells can be found in sand dunes and stream beds all the way up Ninety Mile Beach, often in densely packed deposits. Carbon dating suggests these shells could be over 1000 years old, but some look to be much younger than this.
One suggestion is that they are the only surviving evidence of an extinct race of heavy-shelled toheroa. Then again, perhaps the race still survives, living exclusively below the tides. Some people believe this to be the case. Fishermen off Matapio, a small island north of The Bluff on Ninety Mile Beach, claim to have seen, in relatively shallow water, large toheroa moving on the bottom. Historian Noel Hilliam, who has investigated many of the shipwrecks off Dargaville Beach, is adamant: “I know the toheroa are out there, I’ve seen them.”
Another tantalising piece of evidence is toheroa shells found on Dargaville Beach with small holes drilled in them. The holes could only have been made by carnivorous snails that live offshore. Further light on underwater toheroa may be shed when the research vessel James Cook completes a major sampling expedition in shallow coastal waters of both Northland coasts.
For the shore toheroa, research on larval development and growth in captivity may hold the key to the replenishment of the beds (see box). Let us hope so. It would be sad indeed for future generations never to know the taste that prompted a prince to ask for more.