Identifying critical habitat areas and developing decision making tools for the management and conservation of coastal dolphins

Abstract

Critical and important habitat areas have been defined as those which are crucial to the survival of cetacean populations and as such should be regarded as sanctuaries. There are very few cases, however, where such areas have been identified for coastal dolphin species and even fewer cases where these areas have been integrated into management plans. It is also essential that the exposure to potential threatening processes be quantified in these areas in order for management to have effective conservation outcomes. This study identified and quantified the use of critical and important habitat areas for a population of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in a marine protected area in Byron Bay, Australia. It also quantifies the exposure to encounters with recreational and commercial vessel activity within these areas, an identified potential threat to the long-term welfare of this dolphin population. Seasonal land-based surveys were made with each group of dolphins and vessels recorded using marine mammal tracking software. Dolphins demonstrated heterogeneous use of habitats with variations occurring between group compositions. Groups were observed to utilize a small (5.61km2) shallow protected area significantly more (P < 0.05) which was also used significantly (P < 0.05) more by groups with calves for resting and socializing than adult-only groups that preferred deeper waters. Of all groups observed, 40% had a vessel encounter and 72% of encounters took place in the critical habitat area with an average of 0.90 encounters/hr (S. D. = 1.11). Encounters were significantly (P < 0.05) longer with resting calf groups (¯X = 16.8 mins, S. D. = 17.7) than adult groups (¯X = 10.6 mins, S. D. = 11.5). An innovative decision making tool incorporating risk assessment strategies was developed to aid in the management of the critical habitat area and provide for the long-term welfare of dolphin populations.