Humboldt squid on the move( Over the last five years large preda...)

Over the last five years, large, predatory Humboldt squid moved north from equatorial waters and invaded the sea off Central California, where they may be decimating populations of Pacific hake, an important commercial fish. Ironically, these squid may have benefited from the decline of large tuna and billfish in the Equatorial Pacific, which previously preyed upon and competed with the Humboldt squid for food. This biological shift is documented in an article by postdoctoral scholar Louis Zeidberg of Stanford University and senior scientist Bruce Robison of the Monterey Bay Aquarium Research Institute in the July 31, 2007 edition of the Proceedings of the National Academy of Sciences.

Humboldt squid (Dosidicus gigas) hunt in large numbers along the coasts of both North and South America, from Chile to Baja California. They have occasionally been spotted as far north as San Francisco, but never before in large numbers or over long periods of time. In recent years, mass strandings of Humboldt squid on Southern California beaches have led to speculation that the squid might be expanding their range. This study provides the first scientific records to prove that assertion.

To study changes in the abundance of Humboldt squid in Monterey Bay over time, the authors reviewed video and data from surveys of marine life carried out by Robison and his colleagues at the Monterey Bay Aquarium Research Institute (MBARI). Since 1989, Robison has used MBARI's remotely operated vehicles (ROVs) Ventana and Tiburon to videotape and count the number of midwater animals observed at specific depths in Monterey Bay. The resulting data are stored in a searchable database that allows scientists to determine exactly when and where each animal was seen.

Searching through Robison's survey data, Zeidberg found no observations of Humboldt Squid from 1989 to 1997. During 1997, however, large numbers of Humboldt squid were seen for a year or two after a strong El
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Contact: Kim Fulton-Bennett
kfb@mbari.org
831-775-1835
Monterey Bay Aquarium Research Institute
25-Jul-2007