How do scientists find out what food is available to marine mammals and seabirds? They use a system of special nets called a tucker trawl. The nets open and close at different depths, allowing researchers to sample zooplankton and other small marine organisms that serve as food sources throughout the water column. Watch as researchers demonstrate how a tucker trawl works. Information gathered from tucker trawl sampling is part of an effort by researchers to better understand ocean processes impacted by natural and human-caused changes. By tracking key seabird and marine mammal forage species, national marine sanctuaries can apply the information to protect wildlife; for example, they may redirect large ships away from important feeding areas.