Modeling the potential habitats of dusky, commons and bottlenose dolphins in the Humboldt Current System off Peru: The influence of non-El Niño vs. El Niño 1997-98 conditions and potential prey availability

Abstract

Odontocete cetaceans are important predators in pelagic ecosystems; however, patterns of spatial and temporal distribution in the marine ecosystem off Peru remain unknown for many species. In this study, we modeled the potential habitats for dusky (Lagenorhynchus obscurus), long-beaked common (Delphinus capensis), bottlenose (Tursiops truncatus) and short-beaked common (Delphinus delphis) dolphins using maximum entropy models to two conditions: non-El Niño and El Niño 97-98. Dolphin sightings positions, fishing net hauls with potential prey data, and oceanographic variables from 24 cruises along the southeast Pacific coast of Peru (03°30′S-18°21′S) between 1997 and 2014 were used to model potential habitats of dolphins and their prey. Our modeling predicts that during non-El Niño conditions, the different dolphin species have a segregated distribution according to the physiography. Dusky and long-beaked common dolphins use mainly habitats over neritic zones segregating partially their spatial distribution while bottlenose and short-beaked common dolphins showed potential habitats mainly over the shelf-break and oceanic waters, respectively. During El Niño 97-98, this physiographic segregation was predicted to be maintained by the models although with northward retraction for bottlenose, long and short-beaked commons dolphins. Accordingly, dusky and long-beaked common dolphin potential habitat overlapped mainly with neritic potential prey species (Peruvian anchovy, Engraulis ringens; silverside, Odonthestes regia regia; red squat lobster, Pleuroncodes monodon; common squids, Doryteuthis gahi and mackerels). Bottlenose and short-beaked common dolphin habitats were predicted to overlap mainly with oceanic potential prey (mackerels; Panama lightfish, Vinciguerria lucetia; myctophids; Humboldt squids, Dosidicus gigas and euphausiids). Our results predict that dolphins use specific physiographic areas throughout the Peruvian marine ecosystem and these habitats did not drastically change during El Niño 97-98.