Anthropogenic food patches in the marine environment, such as aquaculture farms and active trawlers, may impact on the behavior of marine mammals through modification of habitats, changes in predation pressure, or alterations in food distribution, availability, and predictability, affecting related social interactions and population demographics. This study examined patterns of association of a population of common bottlenose dolphins (Tursiops truncatus) around Lampedusa Island (Italy) during 1996-2006 and tested the hypothesis that the trawl fishery and the presence of an aquaculture farm could affect such patterns. Here, we used measures of association between pairs of individuals to assess this impact on social unit composition/cohesion and some analytical techniques to describe the structure of dolphin social networks and temporal stability of associations. Association information for 71 regularly sighted individuals was obtained from photo-identification surveys within groups observed or not at ''feeding stations.'' We found association patterns between dolphins were nonrandom. The Lampedusa population seems to be arranged into 6 clusters and organized in communities composed of animals that were either never seen in association with feeding stations (N individuals) or those that are (Y individuals), although mixed assemblages were also recorded. Both communities showed long-term preferred companions, with different degrees of social cohesion-as resulted by network measures and temporal analysis. Delineating community structure at Lampedusa Island has offered basic information for further investigations in the area, also providing novel evidences on how disparities in association patterns between bottlenose dolphin individuals may have resulted from a combination of ecological and anthropogenic factors.

Common bottlenose dolphins, Tursiops truncatus, were surveyed in offshore gas fields off Ravenna, Italy, between Spring and Autumn, 2001-2005. These visual surveys provide the first density estimates of bottlenose dolphins in the Northwestern Adriatic Sea south of the Po River. Since no study has examined the distribution of bottlenose dolphins relative to gas platforms, when dolphins were encountered, their distance from the nearest gas platform was estimated and behaviour was assessed. Dolphins were sighted on ca. 36% of survey trips, which varied in duration from 1 to 6 h. Group size ranged from 1 to~50 individuals, with no seasonal trend evident in the likelihood of encounter. Dolphin density was estimated to be approximately 80% higher within 750 m of gas platforms, relative to densities >750 m from platforms, although variability around the estimates was high. From a limited number of behavioural observations, slightly higher frequencies of feeding and milling behaviour were observed closer to gas platforms, whereas dolphins observed further away exhibited higher frequencies of socialising and travelling. Gas platforms are known to provide habitat for demersal fishes and act as aggregation points for pelagic fishes, and these data provide some support for the idea that bottlenose dolphins may utilise gas platforms opportunistically as feeding sites.

This paper represents the first quantitative assessment of the distribution and abundance of bottlenose dolphins (Tursiops truncatus) inhabiting the waters around Lampedusa Island, Italy. Eleven years of photo-identification data, collected from 1996 to 2006 by three different research groups, were brought together, reviewed and analysed to fulfil the following objectives: (i) to obtain baseline information on the abundance and residency of the local bottlenose dolphin putative population; (ii) to review the current Marine Protected Area (MPA) boundaries, especially those referred to waters around Lampedusa Island, with a view to establish a new Special Area of Conservation (SAC); and (iii) to explore the potential and limits of analysing heterogeneous datasets to improve future data collection methods. The most resident dolphins were regularly observed in six specific areas around Lampedusa Island. From a total of 148 photo-identified bottlenose dolphins, 102 were classified as well-marked. The capture histories and the distribution of sightings clearly show a number of dolphins regularly use the study area. Best estimates for the first period within the ‘core study area’ were obtained for 1998 data. The 2005 estimate was significantly larger than the 1998 estimates (z = 2.160; P < 0.05) compared to that of 1998. Implications of our results for the current MPA, for transboundary conservation initiative involving Italy, Malta and Tunisia and for directing future research within and outside the MPA are fully discussed.

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