The autumn occurrence and spatial distribution of cetaceans in the waters of Mauritania during a geophysical survey in 2012

Abstract

This study aimed to identify the occurrence and spatial distribution of cetaceans in Mauritanian waters (eastern Atlantic). A geophysical survey was conducted over 92 days between September and December 2012. Over 967 km was surveyed, with 1 017 h of observer effort recorded. Visual watches for marine mammals resulted in 228 cetacean sightings of 16 different  species, including 12 odontocetes and 4 mysticetes. The short-finned pilot whale Globicephala macrorhynchus was the most frequently encountered  odontocete, followed by the Atlantic spotted dolphin Stenella frontalis. Of the mysticetes, the sei whale Balaenoptera borealis and blue whale B.  musculus were encountered most frequently. We used generalised additive models and generalised linear models to examine the relationships  between environmental factors and cetacean distribution. The results showed depth had a significant influence on presence of the short-finned pilot whale, which preferred waters deeper than 1 800 m. The model for mysticetes identified bathymetry as a significant environmental predictor, whereas slope of the ocean floor had a positive effect but was not  significant. This study contributes to our understanding of cetaceans in Mauritanian waters, using data from a platform of opportunity.

Keywords: generalised additive model, generalised linear model, marine mammals, mysticetes, odontocetes, seismic data, short-finned pilot
whale, West Africa