Distribution, and Socioeconomic Analysis of Delphinus delphis and Tursiops truncatus in Relation to Vessel Presence in the Eastern Aegean Sea
Distribution, and Socioeconomic Analysis of Delphinus delphis and Tursiops truncatus in Relation to Vessel Presence in the Eastern Aegean Sea
Objective: This study investigates population abundance and distribution of common (Delphinus delphis) and bottlenose dolphins (Tursiops truncatus) in the Eastern Aegean Sea, where there is limited knowledge of these species. Analyses were made in relation to vessel presence and socioeconomic implications. Methods: Data was collected during boat-based surveys, South of Samos Island and the Northern Dodecanese region, Greece, to determine dolphin population abundance and distribution. Interviews were conducted with native stakeholders to determine socioeconomic factors influencing populations. Results: Mark-recapture photo-identification determined 78 and 76 marked individuals for 2015 and 2017 respectively, for common dolphins, and 31 and zero marked individuals for 2015 and 2017 respectively, for bottlenose dolphins. Common dolphin abundance estimates were 147 in 2015 (95% CL= 109-212) and 180 in 2017 (95% CL= 106-323). For bottlenose dolphins, 2015 estimates were 71 (95% CL= 46-120), while 2017 were unable to be calculated. There was no pattern to either species distribution; however, most sightings occurred near Southern Samos. Considering vessel presence, bottlenose dolphins were sighted most in the presence of fishing vessels, while sightings for common dolphins varied. Bottlenose dolphins showed avoidance of areas where vessels were most present in 2017, compared to 2016, whereas common dolphins did not. Despite competition between artisanal fishermen and populations of these dolphins for the same declining resources, stakeholders had similar awareness for views regarding conservation. Conclusion: Future population fluctuations may occur if vessel traffic continually increases, fishing laws are not abided and enforced, and conservation efforts are not recognized. Additional studies, implementing larger survey areas, are necessary to better understand both species’ population structure and distribution and effects of vessel presence. Moreover, more investigation into socioeconomics, between dolphin conservation and the fishing industry are needed to identify how impactive the industry is to these populations and other cetaceans inhabiting the Eastern Aegean Sea.
