In the North Pacific, some of the rush hour traffic is underwater. A new study published in the Journal of Experimental Marine Biology and Ecology finds that sharks around Palmyra Atoll, southwest of Hawaii, have peak travel times on major routes in and out of the lagoons. 

The University of California, Santa Barbara–led study examined shark populations using a type of acoustic camera called dual-frequency identification sonar. Based on the images generated, the researchers found that a deep channel dredged during World War II served as a kind of “highway” for the animals in and out of the lagoon. The camera allowed researchers to see almost 1200 shark sightings over the course of almost a month.

Like human commuters, sharks tended to come and go at around the same time of the day. Shark traffic peaked just after dusk, between 7 p.m. and 8 p.m. each day. Many sharks tend to hunt mostly during the early evening hours.

The study serves as proof that acoustic cameras like this one can be used to effectively study shark behavior, allowing for more accurate monitoring of entire populations than tagging individual sharks would.