Summary:
Striped dolphins are the most common cetacean in the Mediterranean Sea, with a declining west to east abundance gradient (Notarbartolo di Sciara & Birkun, 2010). The species is classified as a regular resident of the Levantine basin, with year round presence (Kerem et al., 2012) and the Greeks Seas (Frantzis, 2009). Its population has been characterized as “Vulnerable” (Aguilar & Gaspari, 2012) by the IUCN (Red List of the IUCN, 2008). Informed conservation management of marine mammals requires an understanding of population size and habitat preferences. For the Greek seas, such data are needed for the assessment and mitigation of anthropogenic impacts, such as fisheries interactions. This study presents large-scale estimates of abundance, density and habitat preferences of striped dolphins (Stenella coeruleoalba) over the area of the Hellenic trench. Using distance sampling analyses, dolphins were estimated to be 6613 (CV = 0.17; 95% CI 4716-9273) derived from 12 years of data. The detectability of striped dolphins was influenced from Beaufort conditions and the group size of dolphins detected. Observations had an effective range of 209 meters with most of the detections achieved in smaller distances. Striped dolphin abundance and density was higher in pelagic waters with higher depths. Habitat modelling also associated striped dolphins with waters of >500 depth, high slope, and higher sea surface temperatures (SSTs). Distributional data should inform management strategies and environmental assessments of potential anthropogenic threats to this protected species. Taking into account that data did not appear efficient for the analysis, the results presented here ideally need to be validated by a more systematic and region-wide survey of the Hellenic Trench. Nevertheless, no previous study has been conducted for the abundance of striped dolphins and these results contribute for further assessments.
Keywords:
distribution,abundance,striped dolphins, Hellenic Trench, distance sampling
