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Animals (Basel). 2020 Feb 6;10(2). pii: E260. doi: 10.3390/ani10020260.

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

Author information

1
Hydrobiology-Ichthyology Laboratory, Department of Ichthyology and Aquatic Environment, University of Thessaly, Fytokou str, 38446 Volos, Hellas.
2
Department of Animal Science, Faculty of Agricultural Sciences, University of Western Macedonia, 53100 Florina, Hellas.

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.

KEYWORDS:

Delphinus delphis; Density Surface Models; Stenella coeruleoalba; Tursiops truncates; distance sampling; marine mammal abundance

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