Halfway between Hawaii and American Samoa lies a group of small islands and inlets. Among them is Palmyra Atoll, an almost 5-square-mile ring of coral.

The lagoons of Palmyra -  part of the Pacific Remote Islands Marine National Monument - provide sanctuary for a variety of mobile species including sharks, manta rays and turtles.

In a new study, UC Santa Barbara marine biologists applied existing technology in a novel way to monitor animals coming into and going out of a lagoon via a deep channel dredged during World War II. Their work confirmed that the route was an important "highway" for sharks and highlighted the magnitude of their channel usage. It also highlighted the time of day when shark traffic peaks. It turns out rush hour for sharks is between 7 and 8 p.m.

The researchers' findings appear in the Journal of Experimental Marine Biology and Ecology.