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Monitoring what seabirds eat could help people manage sardine fishing more sustainably, researchers say.

In the Gulf of California, fishing boats catch small fish such as Pacific sardines. But the amount of fish available can vary wildly over just a few years. The fisheries “have been difficult to manage sustainably, and regional economies have been shaken by their collapses,” the study authors write in Scientific Reports.

Since seabirds also eat these fish, the researchers speculated that the birds’ diets could tip off fishery managers to sardine declines in advance. They studied food regurgitated by California brown pelicans, Heermann’s gulls, and elegant terns in the region and estimated how much of the birds’ meals came from Pacific sardines or Northern anchovies.

The team found that when the gulls’ and terns’ diets were low in sardines, the sardine catch the following season was also likely to be low. A low-sardine diet for pelicans was linked to low sardine catch during the same season.

The results suggest that even when fishing boats are hauling in big loads of sardines, seabirds have already registered the sardine decline and have shifted their attention to anchovies. Keeping an eye on what seabirds are eating “may provide a useful way of monitoring the fishery and forecasting the success of the fishing fleet,” the authors conclude. Roberta Kwok | 26 February 2013

Source: Velarde, E., E. Ezcurra, and D.W. Anderson. 2013. Seabird diets provide early warning of sardine fishery declines in the Gulf of California. Scientific Reports doi: 10.1038/srep01332.

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