The results, to be published online by early March 2006 in the journal Conservation Biology, suggest that feeding further down the food web may have played a role in low levels of reproduction observed in contemporary murrelet populations, and has likely contributed to the seabirds' listing as an endangered species, the researchers said.
"The dietary patterns of today's marbled murrelets might be artifacts of the profound changes that coastal marine ecosystems world-wide have undergone because of overfishing," said Steve Beissinger, professor of conservation biology in UC Berkeley's Department of Environmental Science, Policy, and Management and principal investigator of the study. "What better place to investigate this process than in Monterey Bay, where sardines once were king and Cannery Row formerly stood?"
The researchers decided to embark on this study when they noticed that the population of 600 marbled murrelets they were studying in central California had very low levels of reproductive success.
"You'd expect birds to nest every year, but we found that in some years, as many as 90 percent of the murrelets we were studying weren't nesting," said Beissinger. "Even in the good years, only 50 percent of the seabirds were nesting, and for those that did, many nests failed for a variety of reasons."
The researchers analyzed marbled murrelet feathers from 136 birds collected in the Monterey Bay region between 1895 and 1911. The historic feathers represent a time period prior to the onset of intensive fishing, decades before the infamous sardine fishery collapse of the late 1940s, and nearly a century before recent declines of anchovies, squid and rockfish.
Source:University of California - Berkeley