A sharp decline in baby lobsters offered an early warning of substantial losses in Maine’s Midcoast lobster population, according to a new University of Maine study that connects falling numbers across successive stages of the crustaceans’ lives.
Researchers found that an 80% decline in baby lobsters sampled between 2010 and 2022 preceded declines farther along in the population: a 70% decrease in young lobsters since 2015 and a 50% decrease in adults large enough for fishermen to catch.
The findings show how a shortage of the smallest lobsters can work its way through the population, eventually reducing the number reaching harvestable size. They also underscore the importance of monitoring lobsters years before they enter the commercial fishery.
The study’s midcoast region, extending from Brunswick to the Schoodic Peninsula, recorded the steepest declines in the Gulf of Maine. That broad study area encompasses the waters off Waldo County and much of Maine’s central coast.
The losses followed a substantial boom. From the 2000s to the 2010s, the number of lobsters sampled in the region doubled before the trend reversed.
The research adds to evidence that the Gulf of Maine’s lobster population has declined since the mid-2010s, raising questions about the future of a fishery that generated more than $461 million in Maine landings in 2025.
Published in the journal Marine Ecology Progress Series, the study brought together UMaine researchers and the Maine Department of Marine Resources. Scientists analyzed state surveys that used scuba divers, traps and trawls to sample lobsters at different depths and stages of development.
Comparing those surveys allowed researchers to trace changes from baby lobsters to adolescents and, eventually, adults. The study classified adolescent lobsters as those with shell lengths of 45 to 83 millimeters.
Lead researcher Robert Jarrett II, a recent doctoral graduate who began the work at UMaine, said central Maine provided the clearest evidence connecting changes across life stages. Researchers linked the region’s boom and subsequent decline to warmer water temperatures.
Growth rates also affected how readily those connections emerged. Faster growth in central Maine produced a more consistent pattern, while slower and more variable growth in eastern Maine likely made the relationship harder to detect.
Down East Maine experienced a similar decline in baby lobsters sampled since 2010, but a smaller decline among adults. Findings for adolescent lobsters differed among surveys.
Researchers said fewer sampling efforts in Down East Maine could help explain some of those differences, highlighting a central challenge in interpreting the results: surveys provide valuable evidence, but their coverage and methods influence what scientists can see.
Warming water further complicates that picture by changing where lobsters can live.
In midcoast and Down East Maine, deeper habitats have become more suitable for lobsters as temperatures rise. Lobsters spreading into those areas can become harder to track through surveys that cover limited locations, depths and habitat types.
Previous UMaine research found that lobster population density declined as the animals became more dispersed and shifted the habitats they occupied. The new study reinforces the need to consider those movements when interpreting changes in survey counts.
For fishermen and coastal communities, that distinction matters. A decline in lobsters sampled can reflect changes in abundance, distribution or both. By comparing multiple surveys across life stages, researchers sought a clearer understanding of the broader population trend.
Kathleen Reardon, a study co-author and the department’s senior lobster fishery scientist, said Maine’s monitoring program follows lobsters throughout their life cycle. Partnerships with the fishing industry make the surveys possible, while collaboration with UMaine helps researchers interpret extensive datasets and supplement stock assessment findings.
Southern Maine presented a different pattern. There, the number of lobsters sampled across all life stages has remained relatively stable since 2010, according to the study.
Researchers attributed the regional contrast partly to differences in water circulation. Southern Maine lacks the circulation pattern that brings cold, deep water toward the surface in other regions. Its deeper waters remain too cold for lobsters even as temperatures rise, leaving the area of suitable habitat relatively unchanged.
Those differences caution against treating Maine’s coast as a single, uniform lobster habitat. Temperature, growth, circulation and survey coverage all influence the patterns researchers observe.
Still, the study’s central finding was consistent: declines in baby lobsters preceded decreases in adolescent populations in Midcoast and Downeast Maine, affirming the smallest lobsters’ value as an early indicator for the fishery.
The work follows another recent UMaine study examining a preferred plankton food source for baby lobsters amid concerns about declining food availability and young lobster survival.
Together, the research efforts are helping scientists examine both what happens to lobsters early in life and how those changes may shape the fishery years later.
Even with extensive monitoring, researchers said, differences in survey methods and lobster behavior can make population changes difficult to interpret. Expanding sampling will remain important as environmental conditions shift.
For midcoast communities, the findings give the decline in baby lobsters a consequence extending well beyond the nursery habitat: fewer young lobsters surviving and growing through the population can ultimately mean fewer adults available to the fishing fleet.
This story appears through a media partnership with Midcoast Villager.