As the boat slowly sailed past the St Catherine’s breakwater, on the north-east corner of Jersey, a small flock of Brent geese, winter visitors from the Arctic, took off ahead of us. Clearing the breakwater, our skipper, Richard, revved the motor, sending the inflatable leaping over the first wave and crashing down beyond it, shooting a large cloud of spray to the sides. Though Richard assured us that this was a relatively calm day, one or two of us might well have been pleased that we had not yet had breakfast.

    It was 7.15 am, and though the sky was brightening, the sun had not yet cleared the cloud that hung low over the horizon and almost obscured the French coast. Eight of us had clambered into the Jersey Seafaris boat for the 15-minute, early morning trip to Les Écréhous , a reef of rocks and small islands that lay about ten kilometres from Jersey and thirteen from France. We were accompanied by Gareth, a Marine Biologist.

    The occasional seal bobbed its head above the waves. A flock of oystercatchers flew away as we approached one of the islands. Other rocks were guarded by cormorants and shags. A solitary razorbill ignored us as we sailed past it.

    As the boat ran up onto the shingle beach of La Marmotière, the second largest island, the dawn sun broke through, transforming the drab, flat scene into one of shining facets and sharp shadows.

    Like much of Jersey, Les Écréhous are composed of granite. They and other similar reefs are remnants of a land bridge between England and France that was inundated as the glaciers of the last Ice Age melted. Belonging to the Duchy of Normandy, they became part of England following the Norman Conquest of 1066. Three centuries later, Henry III gave up his claim to the French crown, and Normandy, but held onto the Channel Islands and its rocky reefs.

    Over the centuries, Les Écréhous  were inhabited, at various times, by monks, smugglers and fishermen. Indeed, the houses of the last group still crown the highest rocks and remain in seasonal use. The highest concentration of these dwellings, dating from the 1880s, cluster around a tiny courtyard on the summit of La Marmotière.

    As we scrambled up the shingle, a thin line of surf stretched a few hundred metres across to La Blianque Île. The sea level, however, was dropping fast, and during the minutes it took for us to explore around the houses and admire the luxuriance of the lichens and succulents that covered the granite boulders, it had fallen sufficiently for a broad shingle bank to link the two islands. Elsewhere, previously hidden reefs had become rocks and rocks had become peninsulas.

    The tidal range around Jersey and Les Écréhous  is said to be the world’s second highest, extending, at times, to around twelve metres. This has helped create a unique ecology, such that, in 2005, Les Écréhous  was declared a marine area of international importance under the terms of the Ramsar Convention.

    The extent of the tidal flow, and the movement of currents around the islands has produced very clear, highly oxygenated waters, in which many species of planktonic larvae flourish. The rocky platforms offer shelter, protection and food to a high diversity of creatures. More than 100 fish species have been recorded, which include conger eel, blennies, rays, pollack, bass, Atlantic salmon, common sturgeon and Twaite shad. In addition to seals, there are bottlenose, white-beaked and Risso’s dolphins, harbour porpoise and pilot whales.

    Of more than thirty species of invertebrate living in the mud and sand, half are rare in British Isles waters. These attract large numbers of wading birds, including winter visitors and passing migrants.

    An important characteristic of these waters is that some species are found here at the northern or southern limit of their range. For example, this is the most southerly reach of the beadlet sea anemone. In contrast, it also marks the northerly limit of the giant goby, a Mediterranean fish. Gareth, our Marine Biologist informed us that a small number of the latter confine themselves to a particular pool that becomes exposed at low tide. These gobies leave the pool at high tide, but return to it when the tide falls.

    Some of the species at this limit of their natural habitats are showing signs of genetic variations, resulting from their relative isolations from the main populations.

    We spent more than an hour exploring the linked islands, and sitting on the shingle to enjoy our breakfasts, during which time Gareth explained the ecology of Les Écréhous . Then it was back into the boat for the return trip, as some of us had a second morning appointment.

    The south-east coast of Jersey, stretching from St Helier to Gorey, was declared a Ramsar site in 2000. Here, the seabed is so shallow that at low tide an area of 17.5 square kilometres becomes exposed, making this one of the largest intertidal reefs in the world.

    We drove to La Roque, on the south-east corner of the island and joined a group led by Trudie and Keith, of Jersey Walk Adventures. About two kilometres from the coast, the Seymour Tower stood on its craggy plinth, separated from us by an expanse of sand and mud flats, pools and channels and rock platforms. Some in our party accepted the offer of gumboots, others of us decided we could put up with wet feet.

    We were first taken to the holding cages that contained thousands of oysters, harvested from the beds that lay in deeper waters. The oysters would be held here for a time before being transferred to tanks exposed to ultra-violet light prior to being sent to markets, mostly in France. There were European oysters in the pools, but the farmed ones were American Pacific. Farther out among the rocks were poles festooned with farmed mussels.

    We continued through calf-deep pools and over fields of serrated, knotted and bladder wrack, kelp and carrageen. Trudie pointed out examples of velvet horn seaweed and coralline algae, and tempted us to taste sea lettuce and other rock pool delicacies. She also found a piece of seaweed clustered with small colonies of star sea squirt (botryllus schlosseri), and in one pool, a snake locks sea anemone.

    The pools and channels held myriad  shells, tops, limpets, periwinkles, whelks and the occasional ormer and oyster, half of them abandoned, half still occupied. In one pool, we saw a limpet being predated by a whelk. The roof of a small grotto, formed by boulders, was coated with a layer of orange sponges. A series of incongruous tracks across gravel beds, some of them several metres long, led to stones that had been dragged along by currents acting on bunches of seaweed rooted to them.

    Among the sand ripples were concentrations of what appeared to be dark green algae, but on closer examination, proved to consist of millions of tiny mint sauce worms (symsagittifera roscoffensis) that obtained their nutrition and their colour from a symbiotic alga. Each worm contained around 25000 algal cells.

    We came to a rock on which a large letter P was carved. This, said Keith, dated from 1740, when, following a dispute, the rights to harvest seaweed were granted to the Paine family. Evidence of much earlier, probably seasonal human activity had been found in butchered mammoth bones dating back to Neolithic times, when the land bridge still existed and forests of alder and birch covered the area.

    As we approached the Seymour Tower, a waterspout appeared over the sea to the south. Seeming to form in a lower stratum of cloud, it reached up to a higher, broader cumulus, and hovered there for several minutes before slowly fading.

    The Tower itself was built as a defensive structure during the 18th century, and stands on a tall, granite shelf. It is reached by means of a rough-hewn staircase, and contains seven bunk beds and a stove , with fridge and lighting powered by roof-mounted solar panels. It can be booked by groups of people who are happy to spend a night cut off from the land by the high tides.

    We climbed to the roof, where Trudie hoisted the Jersey pennant while we enjoyed the quite stunning view back over the rocky expanse to the coast. Despite its sometimes being compared to a moonscape, we had found it to be a magical region, teeming with a huge variety of marine life.


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