Effect of boat moorings on seagrass beds near Perth, Western Australia

Abstract

Boat moorings have been found to produce circular scours in seagrass meadows, ranging from 3 to 300 m2. "Cyclone" moorings (which have three anchors and a swivel) are much less damaging to seagrass meadows than "swing" moorings (with a single anchor and chain). The total area of seagrass meadow lost due to moorings totals some 5.4 ha in the Rottnest Island, Warnbro Sound and Cockburn Sound regions of Western Australia, with most loss (3.14 ha) in the Rottnest region. While the relative area of seagrass meadow lost is small (<2%), there is considerable visual impact in some areas. The scours created by moorings in the seagrass canopy interfere with the physical integrity of the meadow. Though relatively small areas of seagrass are damaged by moorings, the effect is much greater than if an equivalent area was lost from the edge of a meadow.