Hydrobiologia 471: 1–12, 2002. L. Watling & M. Risk (eds), Biology of Cold Water Corals. © 2002 Kluwer Academic Publishers. Printed in the Netherlands.
The deep-water coral Lophelia pertusa in Norwegian waters: distribution and fishery impacts
J.H. Fosså, P.B. Mortensen & D.M. Furevik Institute of Marine Research, P.O. Box 1870 Nordnes, N-5817 Bergen, Norway. (E-mail: firstname.lastname@example.org)
Key words: Deep-water coral, Lophelia pertusa, distribution in Norway, fishery impact
The paper presents documentation on the distribution of, and damages to, deep-water reefs of the coral Lophelia pertusa in Norwegian waters. The reef areas have traditionally been rich fishing grounds for long-line and gillnet fisheries, and the coral habitat is known to support a high diversity of benthic species. Anecdotal reports claim that trawlers often use the gear, wires, chains and trawl doors to crush the corals and clear the area before fishing starts. To get an overview of the situation, information about the distribution and damage were collected from the literature, fishermen, and our own investigations. The results show that the corals are abundant particularly on the mid Norwegian continental shelf between 200 and 400 m depth. In general it seems that the largest densities are distributed along the continental break and at ridges of morainic origin. The reports from fishermen suggested severe damage to the corals and in situ observations using ROV confirmed the presence of mechanically damaged corals located on trawling grounds. A first estimate of the fishery impact indicates that between 30 and 50% of the reef areas are damaged or impacted. Fishermen claim that catches are significantly lowered in areas where the reefs are damaged. Potential ecological consequences of the destruction are discussed.
and the associated fauna in Norway was performed by Dons (1944).
Lophelia pertusa (L., 1758) is a stony coral (Scler- actinia) belonging to the family Caryophylliidae. It is distributed throughout the world oceans except in the polar regions (Zibrowius, 1980; Cairns, 1994). The preferred temperature range seems to be 6–8 ◦C (Frederiksen et al., 1992; Freiwald, 1998) and the main depth distribution between 200 and 1000 m (Zib- rowius, 1980; Freiwald, 1998). The shallowest record of a living Lophelia reef is at 39 m in Trondheims- fjorden, Norway (Rapp & Sneli, 1999), while the deepest records extend down to 3000 m in the Atlantic (Squires, 1959).
Seven species of scleractinians occur in Norwegian waters, of which Lophelia pertusa and Madrepora oculata L., 1758 form colonies. Madrepora, however, is less abundant than Lophelia and has never been re- ported to build reefs (Dons, 1944; Frederiksen et al., 1992). Lophelia has been known for centuries to sci- entists and fishermen, especially those using passive gear such as gillnets and long-lines in deep water. The first systematic study on the distribution of Lophelia
The reefs are considered as good fishing places for net and long-line. Fishermen set their gear as close as possible to the reefs, but not directly over them, in order to avoid potential damage or loss of equip- ment. A quite parallel practice is described by Breeze et al. (1997) from Nova Scotia. Although these fishing techniques may cause breakage of corals it is assumed that the damage is of limited extent. Moderate damage probably occurred when the first small bottom trawls started, but the degree of impact probably changed dramatically with the development of larger vessels with powerful trawls, e.g. rockhopper gear, adapted to operate on rough stony bottoms and coral areas.
Bottom trawling on the banks of the Barents Sea started in the 1930s. The activity scaled up in the 1960s by the introduction of factory and wetfish trawl- ers. In the mid 1980s trawling occurred along the continental break and extended further to the banks on the shelf as a result of lower quotas for the Norwegian Arctic cod. It was at the end of the 1980s that rock- hopper gear was developed allowing larger vessels to