The number of young lobsters is declining in the Gulf of Maine despite years of record-breaking harvests, a University of Maine marine scientist has warned.

Rick Wahle quantifies the population of baby lobsters in the gulf, a key lobster fishing area about the size of Wisconsin, at monitoring sites in New England and Canada every year. His American Lobster Settlement Index, released this month, shows monitoring sites from New Brunswick to Cape Cod had some of the lowest levels since the late 1990s or early 2000s.

The decline in baby lobsters represents an “early warning” of what might happen to the future of the lobster harvest, which is a major fishery and a focus of the tourism industry in New England, Wahle said. Lobsters take several years to grow to legal harvesting size, so the drop in young lobsters would start to affect lobstermen in future years, he said.

“If we were to see a collapse in the lobster catch, it would mean that we’re already seven to eight years into a decline in the population,” Wahle said.

For over 10 years now, lobster egg production has been rising but the number of baby lobsters has been falling, Wahle said. Scientists and fishermen are working to better understand the changes in the lobster population and their potential ramifications for the environment and the economy.

Wahle said one factor could be a declining amount of a type of copepod that baby lobsters like to feed on. Another possibility is an increase in predators of young lobsters, he said. Wahle said scientists need to better understand those issues to help prepare for the future of the lobster fishery.