Common dolphin ( Delphinus delphis) habitat preferences using data from two platforms of opportunity

Abstract

Cetaceans are difficult to observe in the wild, and demand complex logistics for dedicated collection of biological data. As such, the distribution of most cetacean species is still poorly understood. Ecological niche models are useful in studying species distributions and their ecological determinants, and platforms of opportunity (e.g. commercial nautical operators) can provide an alternative source for that data in cetaceans. In this study, we modelled common dolphin ( Delphinus delphis) habitat preferences using ecological niche modelling and presence data obtained from distinct platforms of opportunity in two different areas in the Portuguese coast (west and south mainland Portugal) for the period 2005–2007. Models from southern Portugal were projected to western Portugal and vice-versa, to check for robustness in predicting the species ecological niche. Our results show that data from platforms of opportunity can result in robust ecological models and provide extremely useful information on cetacean ecology. We found that common dolphins exhibit a patchy distribution pattern over the Portuguese coastline, and identified key habitats for their occurrence. The most important variable associated with this species' distribution was chlorophyll concentration which, given the results from previous research, we hypothesise reflects an ecological specialisation on pelagic schooling fish. Given that the most abundant schooling fish species in Portugal is increasingly overexploited and in constant decline, more attention should be given to the conservation of common dolphin in Portuguese waters.