Boat traffic in Lampedusa waters (Strait of Sicily, Mediterranean Sea) and its relation to the coastal distribution of common bottlenose dolphin (Tursiops truncatus)

Abstract

The volume of boat traffic and its potential connection to the coastal distribution of the common bottlenose dolphin (Tursiops truncatus) was evaluated off Lampedusa Island (Strait of Sicily). From July to September 2006 daily surveys were carried out at eight sites along the coast, three times a day, to assess the number, type, and size of boats moving, fishing, or stationed in Lampedusa waters. The study area was divided into four geographic areas: northwest, northeast, southwest, and southeast. Data were analyzed to determine the difference in the number of boats among the areas, sampling months, and times of day. The presence of dolphins was monitored by standardized land-based observations. Dolphins (n = 139) from 38 sightings were observed throughout the study period (90 days). In order to compare the presence of dolphins among areas, a relative abundance index was used: A-EH (number of sighted specimens per effort hour). Common bottlenose dolphins appeared to be broadly distributed around Lampedusa, although this study highlighted a possible overlap between their habitat, boat traffic, and fishery, especially in the southwest.