Baby-lobster escorts wanted
FEELING GUILTY ABOUT THAT LOBSTER YOU ATE Now’s your chance to make up for it.” That’s how training officer Hannah pitched a visit to the National Lobster Hatchery to the University of Bristol diving club.
The hatchery is in Padstow, on Cornwall’s north coast, and works to improve the lobster fishery by captive rearing of juvenile lobsters.
Once a batch of lobsters has been reared, they then have to be returned to the wild in a way that encourages as many as possible to survive the process, and continue growing to adulthood.
This is where divers can get involved, by carrying trays of baby lobsters to the seabed and releasing them as close as possible to a suitable habitat.
All very simple in principle, but the logistics soon become complicated.
Once removed from the constantly circulating water of the hatchery tanks, the baby lobsters can survive for only a few hours before having to be released into the sea, so they have to be collected from the hatchery on the morning of their release.
A baby lobster’s favourite food is… other baby lobsters, and they are very aggressive, so they need to be kept separated. The best way to do this is to keep them in the cells the hatchery uses right up until they are released on the seabed. So trays of cells have to be transported to the dive site, with empty trays and cells being returned to the hatchery afterwards.
Lobster cells are arranged into blocks of 6 by 14, or 84 baby lobsters per block, which fits nicely into a shallow plastic crate. A typical release will involve 1000 babies, or 12 crates of 84 cells. This is enough to fill the back of a big estate car.
While lobsters in the past have been released via many ports around Cornwall, and as far away as the Scilly Isles, the club I joined for the day went for the simplest option, to get them straight on a boat from Padstow.
Harlyn Dive School operates from Rock, immediately across the estuary from Padstow.
IT’S A PERFECT JUNE DAY, and already way too hot to sit about in diving suits, when dive-school owners and instructors Steve and Andrew launch their 7.8m RIB. The Bristol University group leave their drysuits off for the short journey across the river to Padstow to collect a batch of baby lobsters. I am already regretting being half suited-up.
A last-minute complication is getting the trays from the hatchery to the RIB, where the only steps suitable for loading are at the opposite end of the harbour.
This is eventually solved by hatchery manager Dom Boothroyd and one of its researchers, using their cars.
By the time everyone has looked round the hatchery, been briefed on the release and loaded the RIB, we’re joined by Fowey BSAC, which has brought its boat along to help out.
A good job too, because, although the dive school’s RIB is coded for 10 divers, the crates of lobsters take up a fair bit of space, and I take up further space with my camera kit. Moving a few divers to the other RIB for the journey out makes things a lot more comfortable.
On a calm day like today, we may have all just about squashed into one boat with the lobsters, but it would have been an awful journey in a rough sea.
Steve has a good site selected, his usual training spot, tucked into a corner at Harlyn Bay and then out round the headland.
The ideal environment for the lobsters is a mixed substrate with patches of coarse sand, silt, gravel and rocks.
The juveniles initially burrow into the seabed. When older, they move on to cracks in the rocks. This site has it all but silt, but then I suppose silt is not that common in North Cornwall.
As the first pair of divers kit up, two sets of lobster cells are removed from their crates and transferred to large, clear plastic bags. Each set has a flat cover held in place with elastic bands to stop the baby lobsters escaping early and attacking each other. The bag helps to keep it all together.
Including the Fowey divers, there is one set of lobsters for each diver and one set spare. Watching the first pair of divers struggle to get the last bit of air out of the plastic bags, Steve modifies the procedure by cutting a corner off each bag for the following sets.
With good visibility and shallow water, I watch the divers against the light sand as they head off for the reef, then watch their bubbles as they catch the gentle current out and round the headland.
Under water, the sets of lobster cells are easier to handle than anticipated. Some divers choose to hold them in one hand, while others tuck them under an arm while swimming. A nearby string
of pots suggests that fishermen consider the area good for fully grown lobsters; both Steve and Andrew have seen younger lobsters here in the past.
FINDING A SUITABLE SPOT, the divers open one set of cells at a time. The bag is pulled back or removed, then the cover peeled back from the cells to allow the babies to swim out. Some duly do so, but others are quite happy, thank you, living in their square plastic cells, and are reluctant to grasp their freedom.
Swimming along with the cover removed and all cells open, a few more come out. Nevertheless, about half of the lobsters remain. This is where strategies become interesting.
Shaking the set of cells has some effect, but also tends to shake the cells apart from each other; they are only clipped together.
Lobster release is interrupted by an impromptu underwater jigsaw puzzle, as cells are clipped together again.
The next idea is to rotate the cells.
The base of each one is a grid, so water flushes through, and baby lobsters spin out.
The only diver to carry a snorkel finds a use for it. Sliding it out from between his mask strap and Tigger hood, with which it colour-co-ordinates nicely, he uses it to encourage the last few baby lobsters to make new homes in the sand and gravel.
Just over 1000 baby lobsters have been released in an area where it is hoped that they can grow and thrive.
As larvae in the open ocean, no more than one of them would have made it this far.
Perhaps, in a few years time, the area from Harlyn Bay to Trevose Head will have a bounty of lobsters for local fishermen to harvest and visiting divers to enjoy for dinner.
I don’t eat seafood, so perhaps I can look forward to plenty of photographic subjects. In the meantime, I will get on with some of the also-bountiful North Cornwall wreck diving with Steve and Andrew.
For information or helping with lobster releases, go to www.nationallobsterhatchery.co.uk. More at www.harlyndiveschool.co.uk and www.foweydivers.co.uk
Female lobsters (hens) lay their eggs in late summer,and keep them under their tails through the winter. A hen lobster with eggs is said to be “berried”.
Some time in the next spring or summer, the eggs will hatch to release lobster larvae as plankton. An individual hen lobster will have up to 12,000 eggs, and hatching of these will be spread across a few consecutive nights.
As the larvae grow, they shed their shells through a series of metamorphic stages. Over a few weeks they will shed their shells three times, so that by stage 4 they are recognisable as tiny lobsters that settle and burrow into the seabed. In the open sea, only 0.005% of the larvae survive to this stage.
The lobsters continue to grow by shedding their shells, or exo-skeletons. With each moult they gain up to 50% in weight, and lengthen by 10-15%.
After about two years, they move on to crevices in the rocks and begin an adult life.
A hen lobster will become sexually mature at between five and seven years, ready to mate, lay eggs and repeat the process.
Regional fisheries regulations prohibit the landing of lobsters that are carrying eggs. The National Lobster Hatchery has been granted special permission to work with Padstow fishermen to hold selected berried lobsters, so that their eggs can be raised by the hatchery.
Hen lobsters are kept in brood tanks until their eggs have been hatched. Each morning, any larvae that have hatched overnight are caught using a sieve, and transferred to the larval rearing area.
They are treated with a mild disinfectant to prevent contamination, then transferred to conical tanks, where water is swirled round to keep the larvae suspended in the water and separated from each other.
During this period they are fed on minute brine shrimps. These are also used as living pills; anything that the larval lobsters need to be fed is first fed to the brine shrimps, which are then fed to the lobsters.
After a few weeks, the larvae have moulted three times and are fully mobile. In the open sea they would be settling to the seabed. In the hatchery they are separated to individual cells within larger trays of water, where they stay until released.
Here the baby lobsters are fed specially formulated pellets of food. It’s a bit like painting the Forth bridge; by the time a technician has finished adding one pellet per cell, it’s time to go back to the start and fish out any uneaten remains, then to feed all over again.
Throughout the rearing process water is circulated, filtered and kept clean to maximise survival.
After about three months, the juvenile lobsters are 2-3 cm long, big enough to be released.
From a fishing boat, they can be flushed down a long pipe to the seabed. When divers are available, the lobsters can be placed more precisely.
About 40% of larvae survive to this stage, an 8,000-fold increase over survival in the open sea.
|RESEARCH & EDUCATION|
The National Lobster Hatchery is also involved in a range of research projects centred on conditions and diet for young lobsters, toxins and diseases, and fishery management. Older and bigger lobsters produce more eggs, so there may be fishery benefits in a maximum landing size for lobsters caught. Young lobsters are also provided to other researchers.
The lobster hatchery has a visitor centre, and provides educational material for schools.
Female lobsters with their thousands of eggs are kept in a tank until they hatch, which happens overnight. Each morning the larvae are caught using a sieve and transferred to a
separate tank; the baby lobsters are kept in individual cells, each receiving a pellet of food; the larvae now look more like small lobsters, growing larger with each moult; they are kept in tanks of swirling water until they reach their third moult.