From Krill to Elephant Seals, Sentinel Species Detect Hidden Ocean Shifts that Forecast Change

New research identifies species that signal changes in ocean ecosystems.

Northern elephant seals weigh in at several thousand pounds and quickly put on more weight when catching squid, fish, and other prey. They feed off the California coast in the so-called “twilight zone” of the ocean (200 to 1,000 meters deep) where sunlight disappears. The ocean’s twilight zone holds most of the world’s fish, but is difficult to assess on a large scale.

However, elephant seals may help. Scientists have found that just as elephant seals gain substantial weight in good times, they gain little when prey are scarce.

A new research paper published in Science recognizes northern elephant seals as an “ecosystem sentinel” that can provide fishing fleets, fisheries managers, and others with low-cost but high-value insight into how the ocean is changing and why. The finding builds on two earlier research papers published last year that help scientists identify which species respond to changes quickly enough to make good sentinels. They also looked at how to assemble a series of sentinel species to inform decisions affecting the West Coast economy and the environment.

The research supports NOAA Fisheries’ mission of tracking and forecast ocean changes that affect commercial and recreational fishing. The insight helps fisheries managers make more timely decisions and accurate decisions about fishing seasons and levels. Ocean sentinels may help gather the data more quickly and at lower cost than research ships, for instance.

The scientists, led by Roxanne Beltran at University of California at Santa Cruz, examined four decades of data on California’s burgeoning northern elephant seal population. They compared those numbers with recorded changes in the ocean and found that even small differences in how much prey mother elephant seals consumed made big differences in their body mass and survival of their pups.