Bryde’s whales (Balaenoptera brydei) in an area of upwelling off Isla San Cristóbal, Galápagos

Abstract

Bryde’s whales aggregate in the Galápagos Archipelago in an area off the north coast of Isla San Cristóbal during periods of upwelling. Seasonally, these whales are locally abundant off San Cristóbal between May and November, except in years when El Niño conditions occur. Field surveys were performed in summers 2013, 2014, and 2016 around San Cristóbal to search for the presence of Bryde’s whales, and to document their spatial relationship with 20 °C isotherm topography. Our surveys found that most sightings of these whales occurred in locations within 3–6 km of shore (water depths 70–300 m), where the 20 °C isotherm depth shoaled to an average of 31 m below the surface. The presence of Blue whales (Balaenoptera musculus), as well as Bryde’s whales was documented during 2016 upwelling. Mother-calf pairs of Bryde’s and Humpback whales were also documented off San Cristóbal in summers 2013 and 2016 and 2014, respectively. We suggest that our three summers of sightings of Bryde’s whales in an area of upwelling indicates that Isla San Cristóbal is important habitat for individuals and mother/calf pairs alike.