Mapping serpulid worm reefs (Polychaeta Serpulidae) for conservation management

1. This study describes investigations into mapping of the biogenic reefs produced by the polychaete worm, Serpula vermicularis, for the purposes of conservation management. 2. Reef distribution throughout Loch Creran, Scotland, was mapped using a diver transect technique and was found to be restricted to a peripheral band, with a mean upper limit of distribution of 2.7 m. The mean lower limit was found to decrease with distance from the mouth of the loch, with a lower limit of 9.3m in the lower basin rising to 6.6m in the upper basin; the likely influence of a corresponding decrease in the upper depth distribution of muds is discussed. 3. Through determination of the mean width of the reef band and coastline length, the areal extent of the reef band was estimated as 108 ha, revealing Loch Creran to harbour the most extensive known development of S. vermicularis reef habitat in the world. 4. The utility of sidescan sonar in mapping serpulid reefs was examined in four of the major embayments. Reef material appeared as characteristic patterning on the sonargrams, with the morphology of individual larger reefs being discernible. 5. Sidescan sonar was found to be particularly valuable for the identification and monitoring of threats to the conservation of serpulid reefs. Sidescan sonar surveying was found to facilitate identification of loss of habitat extent resulting from anthropogenic activities such as moorings, aquaculture installations and dredging and can also be used to monitor the potentially damaging activity of otter trawling. Further improvements in the mode of deployment of sidescan sonar are discussed. © 2009 John Wiley & Sons, Ltd.