Small claws, big impact

Well into their third decade, The National Lobster Hatchery in Padstow, UK, rears the next generations of Cornish lobsters through their early stages, giving this commercially exploited species a greater chance of survival in the wild.

Words and photographs by Lewis Jefferies

Chris Weston holds out a berried lobster hen to show us the eggs around her pleopods, the feathery parts underneath her abdomen. The senior hatchery technician at The National Lobster Hatchery (NLH) in Padstow, Cornwall, UK, reveals that a single female can carry anywhere from 2,000 to 45,000 eggs depending on her size. However, only about one in 20,000 of these is expected to survive when laid in the wild. “When the hen is ready, she will do a headstand to release the eggs. They then naturally float to the surface. In the wild this usually happens at night for safety, so predators can’t see the larvae,” adds Dr Carly Daniels, head of production, science and development at NLH.

We travelled to Padstow to learn more about a unique approach to the conservation of European lobsters. Their ancestry dates to the Jurassic period when their relatives roamed the planet alongside dinosaurs. Believed to live up to 100 years in the wild, the largest European lobster ever landed weighed a staggering 9.3kg and measured 50 inches in length. European lobsters have an unmistakable appearance – dark blue armour with yellow, white, and red markings, large powerful claws and long, red antennae. Every time they moult – around once a year as adults – they may slightly change colour. The species’ mating process is complex; the female must shed her shell before mating. She has a long incubation period lasting for around nine months. The species is one of the UK’s most valuable marine species with many coastal communities relying upon it to make their living. To help support the sustainability of wild European lobster stocks, the NLH opened in 2000 with a simple idea: To rear lobster hatchlings through their smallest stages in a bid to increase their chances of survival in the wild by up to 1,000 times.

With the global human population expected to rise to more than 9 billion in the coming decades, pressure on wild caught fisheries and aquaculture is increasing. Naturally, the demand for lobster has been rising too. These pressures have, according to the hatchery, seen other lobster populations in Scandinavia and the Mediterranean completely collapse. In the UK, the hatchery’s work plays a vital role in making sure that UK stocks don’t follow the same path. Currently, lobsters in the UK are classified as common, but are vulnerable to local overexploitation, according to the The Wildlife Trusts. Stock enhancement initiatives like the one from the NLH complement fisheries management measures to help conserve and sustain exploited commercial species such as the European lobster. With added pressures created by climate change, such as warmer seas, this is an important initiative – a study conducted in the Gulf of Maine found that lobsters had considerably lower survival rates when reared in waters 3 degrees Celsius warmer than normal.

Led by researchers and scientists, the NLH closely works with fishermen, local restaurants, and the community to help maintain a sustainable fishery. When an egg-bearing female is landed, the responsible fisherman will phone the hatchery who will then send a technician out to collect the female lobster. “We usually take them into the hatchery at a later stage in the incubation, when they are ready to hatch their babies,” explains Dr Daniels, who has worked at the NLH since 2004. A female lobster carries her eggs for about nine months during which she constantly fans water over them to maintain oxygen supply and keep water quality stable. Due to the sheer number of eggs one female can carry, the NLH team seeks to extend the natural hatching season of the lobsters to ensure that the breeding tanks aren’t overcrowded. “In the brood system where we keep all our hens, we’ve got two cold water pools that are set to lower temperatures than the other tanks. This allows us to extend the natural hatching season and bring the eggs on when we are ready,” adds Dr Daniels. In the wild, the natural hatching season would normally fall between March and October. Cooling the females slows the development of the eggs and as the eggs are incubated for longer, it gives the hatchery a larger capacity and ability to hold hens at different stages of incubation.

Once the hatchlings emerge, which nearly always happens at night, hatchery staff collect the minuscule lobsters, classed as planktonic in the first two to four weeks of their life, and put them into a larval cone. It swirls them around in the water to imitate the surface of the sea where they are found as larvae. After three days of eating as much as they can, it’s time for their first moulting (they will burst out of their exoskeletons several times in the first few weeks of their lives to grow) and in only three weeks, they will look like perfect miniature lobsters with claws. The hatchery rears juveniles through their first four stages. They are kept in recirculating aquaculture systems which mimic conditions in the wild by keeping them floating. Once they reach their last larval stage, they are then transferred to the Aquahive® systems to separate individuals and prevent cannibalism. “Each Aquahive® can carry around 4,000 animals, and we have a capacity of over 24,000 in total,” says Dr Daniels. “At this stage, they become truly benthic. This means living in close relationship with the substrate bottom, so instead of floating around in the plankton the young lobsters would swim to the seabed and burrow into the sand or gravel where they would stay for two years,” explains Dr Daniels.

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Issue 30
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This feature appears in ISSUE 30: BLEACHED of Oceanographic Magazine

Issue 30
Supported by WEBSITE_sponsorlogos_blancpain
Supported by WEBSITE_sponsorlogos_blancpain

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