Distribution and abundance of the coastal population of bottlenose dolphins (Tursiops truncatus) in Ireland

Bottlenose dolphins (Tursiops truncatus) are a cosmopolitan species of cetacean distributed throughout the world´s tropical and temperate seas. Irish waters contain some of the highest concentration of this species in Europe (Evans, 1992), with widespread and abundant populations commonly found in both coastal and offshore waters (Shane et al. 1986). For management and conservation measures to be effective it is vital that up-to-date information on the population sizes, ranging patterns and spatial distribution. Three genetically discrete population have recently been described in Ireland; one resident in the Shannon Estuary, one inshore or coastal population and one offshore population (Mirimin et al., 2011, Louis et al., 2014) Research on the only known resident population of bottlenose dolphins has been carried out in the Shannon Estuary since 1993 (Berrow et al., 1996), maintaining a photo-ID catalogue of 120 to 140 individual dolphins uniquely marked dolphins using the estuary throughout the year (Ingram, 2000; Englund et al., 2008). However, little is known about the absolute abundance and distribution of the dolphins that inhabits all around the Irish coast. The Irish Whale and Dolphin Group (IWDG) has been collecting sighting records and images of bottlenose dolphins suitable for photo-identification since 2005, showing that this population is highly mobile with re-sightings of the same individuals reported all around the Irish coast, including northern Ireland (O´Brien et al., 2009) with some individuals also reported from Scotland and England (Ryan et al., 2010; Robinson et al., 2012). The research objectives of this study are to: 1. Characterize the distribution of sightings of bottlenose dolphins around the entire Irish coast 2. Provide information of the distribution and movement of individual recognizable dolphins using multi-site, mark-recapture analyses through photo-identification techniques. 3. Estimate the abundance of the coastal population of bottlenose dolphins using Irish waters.