Tailing Blue Whales

An Academy researcher is finding how the largest organism in the ocean depends on some of the smallest.

To study the largest animals on Earth, blue whales, Academy Research Associate Alejandro Acevedo looks for some of the tiniest creatures in the ocean-krill. By first locating these shrimplike crustaceans, the whales' only main food source, Acevedo can narrow in on his leviathan subjects in a deep, vast ocean.

Each spring, large swarms of krill gather off the southeastern coast of Baja California. That's when Acevedo and colleagues jump into their converted fishing boat and motor out into the protected bay to look for krill and whales. The team locates krill swarms with a sonar-based "fish finder," and Acevedo embarks in his own "panga," a small fiberglass dinghy, to locate whales and observe their behavior. When the whales surface for air, Acevedo snaps a photograph to later identify and document individuals by the coloration pattern near their dorsal fins.

Krill are euphausiid crustaceans related to shrimp. Despite their small size they are an important component of many marine food webs because of their large numbers and their tendency to aggregate at times in dense swarms. Photo: Joseph Doughtery

Bathymetric map of Loreto Bay of Baja California, Mexico, showing the location of feeding areas for blue whales and fin whales, a close relative that also eats krill in the region.

A blue whale surfacing after a dive. Blue whales prey almost exclusively on small euphausiids known as krill. Krill tend to aggregate along underwater cliffs about 300 feet deep during the day but at night migrate to the surface. Photo: Juan Carlos Salinas

In the upcoming year Acevedo and his colleagues hope to gain a better understanding of how whale behavior is related to the distribution and life cycle of krill. They will be investigating the energetic costs to whales diving for krill and how that may relate to their prey's abundance.

Acevedo, sixth from left in the back row (white shirt), surrounded by colleagues and students. The research is a collaborative effort conducted in conjunction with Don Croll and Bernie Tershy, University of California at Santa Cruz, Chris Clark, Cornell University, and Jorge Urban-Ramirez, from Universidad Autonoma de Baja California Sur.