Biological impacts of boating at Kawau Island, north-eastern New Zealand

Biological impacts of boating were investigated at Kawau Island, an intensively-used marine anchorage in north-eastern New Zealand. An investigation was made into the impact that the anchoring by leisure boats has on the benthic environment, in particular the fauna. If the damage to the benthic fauna by leisure boat anchoring is leading to the degradation of the local environment, then the expected pattern of use of the harbour for recreational boating is unsustainable. However, if damage could be minimised through the implementation of a management plan at the present time, then the area could continue to be viewed as a recreational resource and be managed for recreational anchoring. The investigation involved the sampling of the benthic fauna to detect disturbance or damage, and to establish the recovery period of the fauna from such damage at present use levels. The pinnid bivalve Atrina zelandica was the most conspicuous macrobenthic organism. Qualitative trends in the intensify of anchoring among sites were generally not reflected in the abundance patterns of organisms. Experimental anchoring of differing intensities damaged Atrina, which were then attacked by whelks and starfish. Anchoring scars persisted for up to 3 months, but had diminished in area and depth after I month. Despite protracted usage, popular anchoring sites are currently not clearly distinct from less popular sites. As intense anchoring is localised in a few bays over a short time, and macrobenthos can recover over the remainder of the year, benthic impacts are unlikely to require management at present. (C) 2000 Academic Press.