Ellie Harrison of BBC’s Countryfile goes ormering around Lihou Island

January 27th, 2012 by Richard Lord

Richard Curtis, Lihou Island Warden, shows Ellie Harrison of BBC’s Countryfile some of the edible seaweeds growing inter-tidally around Lihou Island (click image to expand – ©RLLord)

BBC One’s Countryfile came to Guernsey in early January 2012 to film island life.

Countryfile presenter Ellie Harrison searched the intertidal area around Lihou Island off Guernsey’s west coast for the ormer, Haliotis tuberculata, which is a large marine snail that is a culinary delicacy.

Richard Curtis, Lihou Island Warden, and Ellie Harrison of BBC’s Countryfile look out to sea (click image to expand – ©RLLord)

Richard Curtis of the Lihou Charitable Trust showed Ellie some of the marine species on the shore and Mark Tabel introduced her to ormer gathering.

Mark Tabel searches for ormers around Lihou Island on the 11 January 2012 (click image to expand – ©RLLord)

The ormer is one of 56 species of abalone.

Abalone evolved as one of the earliest snails; they clung to rocks when dinosaurs roamed the earth. The oldest known abalone fossils date back 80 million years although molecular studies suggest that they evolved many millions of years earlier than this.

Abalone survived the last great extinction, which brought the Mesozoic era to a close. Their morphology has been remarkably successful to survive for so long and they have been able to colonise many coastlines around the world.

The ormer, Haliotis tuberculata, moving over rocks covered in coralline algae near Lihou Island (click image to expand – ©RLLord)

Humans have consumed abalone for several thousand years as they provided early coastal communities with an easily accessible food supply.

In ‘Haliotis’, a delightful book about the ecology and biology of the ormer published in 1929, Doris Crofts wrote, “at one time they made a staple food for many savage nations” but during the last century many abalone species declined in abundance as exploitation increased to unsustainable levels.

Haliotis was a name given to abalone by the Swedish botanist and taxonomist Carl von Linné or Linnaeus in 1740. Haliotis comes from the Greek for ‘sea’ and ‘ear’. The shape of the abalone shell resembles the shape of the human ear.

According to many publications, ‘ormer’ is a contraction of the French “oreille de mer.”  So Haliotis and ormer both mean ‘sea-ear’.

Ellie Harrison examines one of the ormers collected by Mark Tabel (click image to expand – ©RLLord)

The ormer lives as far south as North Africa and throughout the Mediterranean. It reaches the northern limit of its natural range in the Bailiwick of Guernsey.

There is a general trend for invertebrates to grow slower but larger in colder water.

Guernsey ormers grow larger than Mediterranean specimens.

Ellie Harrison discusses the technique of ormering with Mark Tabel (click image to expand – ©RLLord)

The ormer can exceed a shell length of 12 cm but they may take 12 years to reach this size in Guernsey waters. On average ormers grow at about 15 mm shell length per year until they reach maturity.

Most of this growth occurs during the warm summer months. Male ormers reach maturity at about 40 mm and females at about 50 mm shell length.

Growth rate slows down appreciably after maturity because more of the animal’s energy is put into reproduction. The smaller mature females produce several thousand eggs per year but the largest females can produce several million eggs.

Ellie Harrison tries her hand at ormering with the assistance of Mark Tabel (click image to expand – ©RLLord)

Ormers don’t mate. Male and female ormers release their sperm and eggs directly into the sea where fertilisation takes place. The larvae stay in the water column only a short time before settling to the bottom.

This means that ormers do not have the ability to disperse over a wide geographical area from one generation to another.

Dr. Daniel Geiger, who is a world authority on abalone, says that larval dispersal is only on the order of ten to 100 metres, which has implications for stock management.

Crustose coralline algae that cover rocks in pink at extreme low water produce a chemical attractant that causes ormer larvae to settle.  The newly settled larva uses its rasping tongue to clean the surface of the coralline algae of fouling organisms.

Doris Crofts writes “minute ormers are coral pink, mottled with grey and white – a convincing imitation of the coralline algae and scattered tubeworms so abundant on the under surfaces of grey granite rocks found at the extreme limit of low tide.”

A young ormer displays the shell colour of the algae it grazes on (click image to expand – ©RLLord)

Larger ormers prefer to feed on more delicate, lacy red seaweeds. Ormers require a regular supply of drifting seaweed, which they catch by stamping down on it with their shell and their muscular foot. Their foot is immensely powerful and once it tightens onto a rock it is very difficult to remove.

According to statistics held by Guernsey Sea Fisheries, during one low tide in 1965, 400 Guernsey shore gatherers harvested about 31,000 ormers.

During the 1967 season shore gatherers harvested close to 200,000 ormers and divers collected an additional 250,000 ormers in Guernsey waters but since then local harvests have fallen appreciably.

In 1876 Guernsey imposed the first regulations to limit the harvest because of a decline in ormer abundance.

For thirty years from the 1860s summer temperatures were below the long term average.

Cool summers can inhibit the ormer’s ability to reproduce and abnormally low winter temperatures, such as occurred in the winter of 1963, can kill ormers.

Ormers grow best at a seawater temperature of 20˚C, which is not yet reached in Guernsey.

Ellie Harrison emerses herself in the sea in search of the ormer (click image to expand – ©RLLord)

Dr. Robert Forster who studied the ormer in Guernsey over several decades thought that the decline in the Guernsey ormer population during the 19th century and again in the 1920s and the 1960s was probably because of periods of below average temperatures particularly during the summer months. “The recruitment of juvenile ormers is crucial to the maintenance of stocks,” he wrote.

To try and aid stock recovery, Guernsey banned diving for ormers off the island’s west coast in 1964 followed by a complete diving ban in 1973. There was also a ban on ormering during 1974, 1975 and 1976.

Even with these past regulatory efforts and the current restrictions placed on shore gatherers the ormer population hasn’t recovered to historic levels.

Sub-tidally the ormer population may be healthy but relatively few ormers live inter-tidally.

Ellie Harrison searching for ormers under a boulder (click image to expand – ©RLLord)

During the last two decades Guernsey sea temperatures have been more suited to the ormer’s requirements.

All ormers reach maturity well before they can be harvested so one would expect that the population should be growing but this doesn’t seem to be happening.

According to Dr. Geiger, ormers may not reproduce successfully if they are not living in higher enough densities. “Because ormers shed their sperm and eggs into the sea, if individual ormers are spaced too far from one another, there may not be successful fertilisation despite them spawning.”

If fertilisation does succeed the larvae have to find a place to settle. Their preferred substrate is crustose coralline algae, which they feed on. Research has shown that coralline algae attract ormer larvae with a chemical scent.

Ormer larvae swim for short periods and then rest and settle to the bottom. If the substrate they settle on isn’t suitable they swim up again, and then come down on another spot.

During ormer gathering many people leave boulders overturned. The tops of these boulders are often covered with crustose coralline algae, which the ormer larvae prefer to settle on.

Ellie Harrison searches for ormers in the waters around Lihou Island on 11 January 2012 (click image to expand – ©RLLord)

“Crustose coralline algae will suffer when there is a disturbance to the under-boulder habitat and this will cause the natural recruitment of ormers to suffer,” said Professor John Ryland of the Marine and Environmental Research Group at the University of Wales.

When the boulder is turned over and not returned to its original position, the bottom of the boulder, which is usually covered in tubeworms, is exposed. This surface is less suitable for larvae settlement.

Leaving boulders overturned kills large swathes of coralline algae.

Coralline algae must be preserved to maximise the successful settlement of ormer larvae.

In 1927 Doris Crofts wrote “disturbance of rocks bearing the seaweed food of Haliotis is mainly responsible for the shortage in Guernsey.”

And in 1975 visiting marine biologist Dr. Foster wrote “that unless there is a considerable reduction in the amount of boulder disturbance any improvement in ormer stocks will be very soon lost.”

Ellie Harrison finds a spiny starfish, Marthasterias glacialis, while searching for ormers. Ormer gatherers have reported a noticeable increase of this predatory starfish inter-tidally off Guernsey’s west coast during January 2012 (click image to expand – ©RLLord)

Countryfile featuring Guernsey will air on BBC One beginning at 7 pm on Sunday 29 January 2012.

 

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