Invaders of the Deep

Forest and Bird, Issue 295, 1 February 2000, Page 7

Invaders of the Deep

ix potential pests of the marine environment have been identified by the Ministry of Fisheries. A new guide ‘Beware invaders of the deep’ has been published by the Ministry which seeks public help in keeping an eye out for unwanted species. The potential pests species include crabs, a starfish, a clam, a fanworm and a green seaweed. They could be introduced to New Zealand in ballast water carried by ships, on hulls or fishing gear, or in a ship’s seachest — a cavity around the water intake of a vessel where organisms can attach. Several have already reached Australian shores where they have taken over extensive areas. The species most feared are: ¢ Mediterranean fanworm, forming high-density beds displacing other species, and fouling marine farms and boats, in shallow seas and hard seabeds within harbours. e European shore (or green) crab, an animal of sheltered rocky shores which attacks a wide range of sea creatures and threatens scallop and mussel industries. e Northern Pacific seastar which threatens aquaculture and

marine biodiversity generally, as it has done in southern parts of Australia. e Chinese mitten crab which threatens marine communities and freshwater riverbanks, digging holes and causing the riverbanks to collapse. While it carries a lung fluke which affects people, the crab is a food source for some and there are fears of deliberate introduction. e Asian clams reach population densities of more than 25,000 a square metre, smothering other bivalves. e Green seaweed smothers other plant life in shallow waters, and is used in aquaria. The fear is it could be brought into New Zealand by enthusiasts and escape into the wild environment. For the watchful beach wanderer, copies of the illustrated guide are available from biosecurity officers at the Ministry of Fisheries. (0800 INVADERS). The effect of foreign organisms in our waters has been amply demonstrated in recent years by the spread of the waterweed undaria, the date mussel, and by the Pacific oyster which has taken over the habitat of the northern rock oyster.