Sam Fraser-Baxter heads to the Wairarapa for one of New Zealand’s longest-running marine surveys – counting baby
On a calm, sunny day, Riversdale beach is a paradise.
While the rest of the Wairarapa beaches are rugged and rocky, Riversdale is a beautiful stretch of sandy coast; a
reprieve from the harsh elements that characterise one of New Zealand’s wildest coastlines.
The golden sands have been a drawcard for holidaymakers for decades. Today, though, a tiny, unassuming critter hiding in
the shallows is the reason Dean Stotter and Jeff Forman are visiting. The NIWA researchers have travelled to the
Wairarapa from Wellington once a month for more than 20 years to survey populations of puerulus – the young, translucent
post-larval stage of the spiny red rock lobster.
A prized delicacy, rock lobster is a highly lucrative industry in New Zealand worth more than $200 million in exports
annually. Understanding the year-to-year settlement of puerulus on our coasts helps to shape our management of the
Dean and Jeff’s work in the Wairarapa is part of a wider study investigating puerulus settlement at seven key sites
around New Zealand including Gisborne, Kaikoura and Stewart Island. Established in the late 70s, the project is one of
New Zealand’s longest running marine surveys.
At the end of October, Dean and Jeff are relieved to be working under a blue sky on a windless morning.
The survey can only be carried out at low tide when the puerulus collectors sit in about 1m of water. Two hours before
or after low tide means working in water too deep to haul them. Each month, the scientists have a three-day window to
choose from. The day with the least swell and wind is best.
But of course, this is the Wairarapa.
Through the winter months, surging swells and bitterly cold winds are a day-to-day reality. Even at the peak of summer,
sudden shifts in the weather can turn a beautiful day ugly. Despite the wild conditions in the region, Jeff says the
pair have a pretty good track record.
“Since Dean and I have been doing the surveys, we’ve only missed one month due to bad weather.”
Today, the normally relentless Wairarapa winds have let up. Jeff and Dean don their wetsuits and wade out to the
Dean lifts a collector onto a rock to count the puerulus. The collectors are rudimentary and reliable. Developed in the
70s – at the start of the project – the collectors consist of plywood boards attached to a metal weight. The boards sit
closely together, creating a perfect place for puerulus to safely settle and hide from predators.
“The first thing they want to do is hide. They’re looking for an ideal habitat and that’s what we’re providing with
these collectors,” explains Jeff.
A long knife is used to scrape out the puerulus into a catch bag for counting. Dean sorts through the weed, crabs and
other marine species to count the puerulus. He jots down the count, releases the puerulus into the water and moves on to
the next collector.
It’s a no-frills kind of science; no computers, no flashy gear, no complicated experiments. The equipment has hardly
changed since the survey started. And for good reason. Using the same collectors maintains scientific consistency, so
the researchers can accurately compare year-to-year trends in puerulus settlement.
When each of the nine collectors have been counted, Jeff and Dean wade back to shore, pack up the gear and hop back into
the truck without changing out of their wetsuits. The tide has turned and time is ticking. With the windows down, they
set off for Castlepoint, the second survey site in the region.
The life cycle of spiny red rock lobster is a journey of epic proportions.
After mating, females carry thousands of fertilised eggs under their tails for 100-150 days. In spring, the eggs hatch
as tiny larvae that are carried by currents out to sea. For the next one to two years, the larvae are at the mercy of
the ocean. Some larvae will drift as far as 1000km offshore.
After developing into puerulus – about the size of a small shrimp and transparent in appearance – they begin to swim
back to shore. How the puerulus navigate their way back to shore is a bit of a mystery. Following the sound of waves
breaking on the coast is one theory.
At the coast, puerulus settle in cracks and crevices in shallow water where they will moult and develop into juvenile
crayfish. The number of individuals that survive the journey and grow into legal sized crayfish will determine the size
of the fishery in years to come.
“There can be big differences annually. That’s what we’re trying to detect,” says Jeff.
There is a phenomenal amount of puerulus settling on the south-east coast of the North Island.
The Wairarapa eddy – a huge anti-clockwise rotating current 200km offshore – is believed to be the reason, trapping and
holding larvae as they grow into puerulus.
The second survey site is tucked inside Castlepoint; a dramatic stretch of coast formed by sandstone and sculpted by
wind and waves. Popular with tourists and fishers, crowds come to visit the iconic lighthouse and cast a line from the
As they arrive, so do the Wairarapa winds. Sheltered from the southerly breeze under the lighthouse cliff, Dean and Jeff
enter the water.
Several fur seals emerge from the shade and join the researchers in the water. Dean and Jeff are unfazed – they smile
and like clockwork, make their way through the site; hauling the collectors, scraping out wriggling puerulus and
Since joining the study in the ‘90s, Dean and Jeff have seen fluctuations in puerulus settlement. A range of factors
including ocean storminess and climate can impact the number of puerulus surviving the journey to the coast.
Recently, puerulus settlement has been very good in the Wairarapa.
When the sampling is finished, Dean and Jeff walk back to the beach, following the cliff line underneath the Castlepoint
lighthouse. They peel off their thick dive-wetsuits, pack their gear and climb into the truck as the sun drifts behind
the Wairarapa hills. They’ll be back again in a month.