Model-Based Distribution and Abundance of Three Delphinidae in the Mediterranean

Abstract

Monitoring of Delphinidae species population patterns in the Mediterranean Sea was carried out in a sequence of surveys employing different approaches. Data from seven-year surveys with small catamaran sailing boats were analyzed under model-based approaches. Density Surface Models were used to produce spatial distribution prediction of three Delphinidae species (Stenella coeruleoalba, Tursiops truncatus, and Delphinus delphis) in an extended study area covering much of the Mediterranean Sea. A classical distance sampling protocol was applied in order to calculate the detection probability of clusters. Static (depth, slope, distance from the coast, and distance from isobaths of 200 m) and nonstatic (sea surface temperature and chlorophyll) variables were used to predict the species distribution/abundance in a generalized additive model context. Stenella coeruleoalba was found to be the dominant species, with an extended distribution in the study area; its abundance was significantly affected by both depth and distance. Tursiops truncatus and Delphinus delphis illustrated a significant abundance correlation with depth and chlorophyll, respectively, while both species showed a robust longitude correlation. Our model pinpoints the significance of nondesigned transect line surveys, suggesting the importance of specific habitat areas for future monitoring and conservation aspects of marine mammals.

The conservation of the endangered Mediterranean common dolphin (Delphinus delphis): Current knowledge and research priorities

“…The Mediterranean Sea, covering approximately 2,500,000 km 2 , has, with few exceptions, narrow continental shelves and large areas of open water, with an average depth of 1,460 m (Coll et al, 2011 summer acoustic pollution, distance from mud deposits). Most of these parameters have been and continue to be modelled against common dolphin presence and distribution in Mediterranean research areas, with increasing publications in recent years (Bonizzoni et al, 2019;Cañadas & Hammond, 2008;Cañadas & Vázquez, 2017;Gannier, 2021;Giannoulaki et al, 2017;Giménez et al, 2017;Giménez, Cañadas et al, 2018;Karamitros et al, 2020;Moura et al, 2012).…”

“…The common dolphin was recently reported to be rare in the middle latitudes of the Western Mediterranean after a study that used both non‐designed longitudinal transect line surveys across the Mediterranean between 2003 and 2007 and a designed zigzag transect survey from 2018 to 2019 (Karamitros et al, 2020). However, small‐boat dedicated surveys carried out between 1988 and 2012 described the distribution of common dolphins in five French maritime regions and three southern regions of the western basin, thus providing observations of this species in the Western Mediterranean, beyond the Alboran Sea (Gannier, 2021).…”

“…As for time‐varying conditions, the chlorophyll concentration has been indicated as a possible factor affecting the distribution of the common dolphin, where it has been examined in the Mediterranean (Cañadas & Hammond, 2008; Karamitros et al, 2020; Moura et al, 2012). The rich chlorophyll concentration may result in a higher incidence of zooplankton, possibly influencing the amount of pelagic schooling fish which also constitute common dolphins' prey (Solanki, Mankodi, Nayak, & Somvanshi, 2005; Ware & Thomson, 2005).…”

Current State of Knowledge and Conservation Perspectives on the Cetaceans of the Aegean Sea

“…Only a few studies have so far investigated biotic and abiotic factors affecting cetacean distribution in the Aegean Sea [27][28][29][30][31][32][33]. Owing to this scarcity of information, our inferences on drivers of cetacean distribution are mainly based on (1) sighting and stranding data in the Aegean Sea and (2) relevant data on drivers of distribution from other areas of the Mediterranean Sea.…”

Αλιευτική Δραστηριότητα Και Στρατηγικές Διαχείρισης Της Μικρής Παράκτιας Αλιείας Στα Δωδεκάνησα

“…2.1.Περιοχή μελέτηςΣύμφωνα με το Κόκκινο Βιβλίο των Απειλούμενων Ζώων τηςΕλλάδας (2009), στα θαλασσινά νερά του Αιγαίου έχουν καταγραφεί 447 είδη ψαριών και χιλιάδες είδη άλλων οργανισμών όπως αστερίες, αχινοί, αχιβάδες, μύδια, στρείδια. Επίσης έχουν καταγραφεί 15 είδη θαλάσσιων θηλαστικών όπως η μεσογειακή φώκια (Monachus monachus), με πληθυσμό που δεν ξεπερνά τα 350 άτομα, το ζωνοδέλφινο, το κοινό δελφίνι(Karamitros et al, 2020), η φώκαινα ενώ σπανιότατα εμφανίζονται και ορισμένα είδη φαλαινών. Η αλιεία αποτελεί παραδοσιακό κλάδο οικονομικής δραστηριότητας για την περιοχή των Δωδεκανήσων στο νοτιο Αιγαίο (Περιφέρεια Νοτίου Αιγαίου, 2013).…”