Diving can be a commercial activity for the harvesting of benthic species, as mentioned above. However this is not widespread, and should generally not be taking place within an SAC. Recreational diving is much more widespread, is common within many SACs, and its effects need evaluation.

Diving can damage CFT communities in two ways. There can be direct damage as a result of the collection of animals either for food, or as souvenirs. The impacts will be of exactly the same type as from commercial harvesting (see above). The collection of specimens by sports divers is generally to be discouraged, and this concept is incorporated in the codes of practice of many diving organisations, for example: "Be conservation conscious....Do not bring up sea-fans, corals, star fish or sea urchins".

Indirect damage is a more pervasive problem, and can result from anchoring of dive boats, and from accidental damage by the divers themselves. Dive boats are generally lighter than commercial boats, and use correspondingly lighter ground tackle, but the cumulative effects in heavily used sites will be damaging. One solution could be to install permanent mooring points in popular areas, so that anchoring would not be necessary.

The damage from divers themselves whilst underwater is largely a result of inexpert techniques, and can be reduced by training, and by diver education programmes pointing out the problems that they can cause. It is by no means clear how much damage divers do cause within British CFT biotopes. On coral reefs in the tropics there is clear evidence that the damage can be substantial and result in serious degradation of reef quality (Hawkins, 1991, and references listed therein). However, the brittle and often fragile nature of hard corals contrasts with the generally more robust and flexible nature of CFT species. Also some of the obviously-damaged reefs are subject to very high visitor numbers, up to 6000 a day in the Key Largo Marine Sanctuary (Ward, 1990). British CFT communities are protected from such vast numbers by their depth, low water temperatures, and in many cases their difficulty of access, and much lower usages are recorded. In the Lundy Island Reserve the minimum estimate for 1997 was 2265 ‘diver days’ (Liza Cole, Lundy Warden, Pers. comm.). For the Skomer reserve the annual number of ‘diver days’ has ranged from 1745 to 3338 over the past ten years (Skomer MNR Annual Report for 1997). The above factors mean that mostly more experienced divers make up the bulk of the visitors. Nevertheless, the lack of evidence of obvious damage (systematic surveys for this seem to be lacking) should not be a reason to avoid caution and care. There are delicate and spectacular CFT species such as sea fans and the bryozoan Pentapora foliacea, which divers could easily damage. There is also the disturbance factor, by which frequent diving could alter the behaviour patterns and approachability of the mobile species within the community.

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