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The deep-water coral Lophelia pertusa in Norwegian waters: distribution and fishery impacts - page 10 / 12





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to its northern limit in R1 while the continental shelf is narrow and therefore provides less area of suitable substrate in R4. The link between the number of re- ports of coral areas by fishermen and the distribution of coral reefs and good fishing grounds is clear.

from trawling to the fishermen and authorities in an understandable way. Based on the results in Table 3 we therefore conclude that the damage of coral reefs in Norway amounts to between 30 and 50% of the total area.

Damaged areas

Impact on coral populations

Damaged corals were present in all inspected localit- ies except for Maurdjupet. It has been impossible to perform direct quantitative observations of how much of a reef or reef area has been impacted or destroyed. For instance, on the shallowest part of Sørmannsneset where only fragments of dead Lophelia spread around without evidence of living colonies in the surround- ings were observed (Fig. 4), one can safely conclude that the colonies have been wiped out. Otherwise, the extent of the damage given here is the best possible estimate allowed by the methodology. The few reports on damage in R4 probably reflects the low number of reefs, most of them localised in the fjords where trawling is forbidden. Because of the inherent limita- tions of the methodology, the present estimates of total coral areas are to be considered as preliminary and should be confirmed by future surveys. Still, this paper presents the first indication of the scale of the problem. It has been important to express the extent of impact

Increased mortality is the most obvious effect from mechanical impact by for instance bottom trawling. The corals are crushed or buried, and wounds in the tissue and possible microbial infection may also re- duce the health of the corals. It is not possible to evaluate the impact that destroyed reefs on the shelf have on coral populations. On a scale from intact to extinct there may be a point below which corals will not be able to maintain populations. The effect will also depend on the reproduction potential, but at present very little is known about the sexual reproduc- tion of the species (Rogers, 1999). It is reasonable to assume that they have a planktonic larva similar to their tropical counterparts (Fadlallah, 1983). Evid- ence of this is found in the North Sea, where corals have colonised submerged components of oil rigs, far away from known locations of colonies (Bell & Smith, 1999). A long-lived planktonic larva may facilitate recolonisation of damaged coral areas.

Figure 8. Two ropes belonging to a gillnet are seen in the lower part of passive fishing gear such as anchored longlines and gillnets. Iverryggen

the picture. Lophelia pertusa reefs are also damaged and torn apart by 17 May 1999 at 200 m depth.

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