Harbour porpoises in the Aegean Sea, Eastern Mediterranean: the species’ presence is confirmed

A-C Cucknell,A Moscrop,A A Öztürk,A Frantzis,O Boisseau,M Romagosa,P Alexiadou,A M Tonay,C Ryan

doi:10.1186/s41200-016-0050-5

Abstract

Results are presented from the first systematic visual and acoustic line-transect survey for harbour porpoises in the Thracian Sea, northern Aegean Sea. During the vessel survey, undertaken in summer 2013, porpoises were observed on nine occasions and detected acoustically 16 times, with a total of 21 distinct encounters recorded. Harbour porpoises were encountered in three discrete blocks: north of the Island of Thasos, Greece; south and west of the city of Alexandroupolis, Greece; and in Saros Bay, Turkey. Saros Bay exhibited the highest relative acoustic encounter rate of harbour porpoises, and porpoises were observed visually there on two occasions 14 days apart, in small groups, one of which included a mother-calf pair. A comprehensive review of stranding records is also presented. The three areas identified as harbour porpoise habitat in this study coincide with the highest number of recorded stranded animals. This paper is the first to report free-swimming harbour porpoises in the Aegean Sea since 1993, and the first time ever in Turkish Aegean waters. Now that the presence of harbour porpoises has been documented, international cooperation towards long term monitoring and management measures are urgently required in order to conserve this vulnerable population.

Highlights

Harbour porpoises (Phocoena phocoena, Linnaeus 1758) are distributed widely throughout continental shelf waters of the Northern Hemisphere and are present in the eastern North Atlantic Ocean and Black Sea (Gaskin 1984; Read 1999; Hammond et al 2013)
Acoustic and visual harbour porpoise survey The harbour porpoise survey of the northern Aegean Sea included 2845 km of transect which utilised at least acoustic effort, 529 km with both visual and acoustic effort and 845 km with both double platform visual effort and acoustic effort (Fig. 2)
This study represents the first dedicated survey for harbour porpoises conducted in the Mediterranean Sea

Summary

Introduction

Harbour porpoises (Phocoena phocoena, Linnaeus 1758) are distributed widely throughout continental shelf waters of the Northern Hemisphere and are present in the eastern North Atlantic Ocean and Black Sea (Gaskin 1984; Read 1999; Hammond et al 2013). The historical presence of harbour porpoises in the Mediterranean Sea has been debated in the past (Frantzis et al 2001, 2003; Notarbartolo di Sciara 2002; Rosel et al 2003; ViaudMartínez et al 2007; Fontaine et al 2012). It is likely that the increase in harbour porpoise records in the Aegean Sea during the last two decades is due to an increased effort in reporting of stranded animals from coordinated stranding networks and improved public awareness of marine mammals (Rosel et al 2003), a genuine increase in the number of individuals in the region cannot be excluded.

Methods

Results

Conclusion