PENTWATER, Mich. (AP) — Scientists are retrieving data from an underwater robot for the first time since it was deployed to gather information about the Lake Michigan fish food supply.

The U.S. Geological Survey and the Monterey Bay Aquarium Research Institute launched the vehicle Aug. 1. It is measuring volumes of algae and tiny animals called zooplankton, which form the base of aquatic food chains.

Experts say the findings will help develop estimates of how many predator fish Lake Michigan can support. They say it’s been hard to develop accurate measures of algae and zooplankton using conventional technologies.

The robot will ply the southern portion of the lake for 25 days, at depths ranging from 9 feet to 150 feet. It’s being removed temporarily Tuesday so scientists can download data and recharge the battery.