WHAT’S UNDER YOUR BOAT? A pocket ID guide to selected non-native marine species
Introduction Dealing with non-native invasive species costs the UK economy in the region of £1.7billion each year. With this in mind, this pocket guide details six non-native invasive marine species yet to become established in the Medway Swale Estuary, in the hope that those found can be dealt with as soon as possible. Please keep the booklet onboard your boat, as a reference, should you come across anything unusual. Please encourage others to pick up a copy, so that they can do the same. Report any sightings as soon as possible using our online form at www.msep.org.uk please provide a photo. For more information on non-native invasive marine species visit www.nonnativespecies.org or www.marlin.ac.uk For advice on reducing your impact on our waters, visit www.thegreenblue.org.uk
American tingle or 0yster drill (Urosalpinx cinerea) What is it? A small predatory snail that feeds on native oysters by drilling through their shells. First reported in 1927, its distribution appears to be limited to the Kent and Essex coasts. Description • Tall conical yellowish or grey shell (sometimes with brown irregular marks), with a sharply pointed spire, up to 4cm high and 2cm broad. • Up to eight rounded whorls with pronounced ridges and ribs. • Oval aperture, with an open canal at the base. Habitat Lower shore and shallow subtidal waters (to depths of between 12-15m), with a reported preference for the muddy bottoms of estuaries.
Email msep@medway.gov.uk for further copies of this booklet. © KWT
Carpet sea squirt (Didemnum vexillum) What is it? A highly invasive non-native marine animal, thought to be originally from Japan. By smothering native species, it not only poses threats to conservation but also to the fishing and shellfish industries. Description Whilst similar to some native species, the following characteristics are useful for identification: • It has a uniform pale orange, cream or off-white colour. • The surface has a firm leathery texture, with a veined marbled appearance. • Its surface has numerous open small pores, which close up out of water to produce pale spots. • It can grow either as thin flexible sheets or hang down in long rope-like growths.
© CCW
© CCW
Habitat Shallow waters, such as harbours and marinas. Usually found growing on hard surfaces, including the underside of jetties and boulders.
© KWT
Veined rapa whelk
Killer shrimp
(Rapana venosa)
(Dikerogammarus villosus)
What is it? A large predatory snail, not currently believed to be established in the UK, though several were caught in the southern North Sea in 2005. Where established, it has been responsible for the decimation of native oyster, scallop and mussel populations.
What is it? A highly voracious predator, which kills invertebrates and small fish. It quickly dominates the habitats it invades, often significantly altering their ecology.
Description • Dark veined knobbly shell, with an orange interior. • Can grow up to 18cm in length. • Large shell opening with small teeth on the outer lip. Habitat Open water systems (including estuaries), on or under soft sediment. Hard surfaces may also be used for breeding, laying eggs and by individuals. It is able to tolerate low salinity, pollution and oxygen deficiency. © George Chernilevsky
Habitat Still or flowing fresh or brackish water, often among hard surfaces or vegetation. Description • Larger than our native shrimps, Commonly 10-20mm in length but can grow up to 30mm. • A key feature is the presence of cone-shaped protrusions on its tail. • It often has a striped back.
© Environment Agency
© Environment Agency
Wakame or Japanese kelp
Wireweed
(Undaria pinnatifida)
(Sargassum muticum)
What is it? A large seaweed, native to the cold temperate areas of Japan, China and Korea, first recorded in the UK in 1994. It may compete for space with native seaweeds and fouls jetties, vessels, moorings and buoys.
What is it? A highly distinctive seaweed, native to the shores of the north-western Pacific. It competes with native seaweeds and seagrasses and is a nuisance to harbours and marinas, where it can become entangled in boat propellers.
Description • Brown in colour. • Stipe (stem) has very wavy edges or ruffles at the base. • A broad blade, flattened with a distinctive midrib. • Between 1-3 metres in length.
Description • Olive-brown in colour. • Often over 1m in length. • Tough wiry stipe with regularly alternating branches. • Small, flattened oval blades. • Spherical gas bladders. • Lateral branches hang like a washing line, out of water.
Habitat Found on hard surfaces, including man-made structures, from the low-tide mark down to a depth of 15m in clear water. May also attach itself to bottom dwelling creatures, empty shells, loose cobbles and other seaweed creatures.
Habitat Hard surfaces in shallow waters and intertidally, particularly in rockpools. It can also tolerate estuarine conditions.
© John Bishop
Spherical gas bladders
© GBNNSS
© SNH
For further information on these species and others to look out for, visit www.msep.org.uk where you can also report your sightings using our online form.
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