The future of Maine’s lobster industry may depend on a creature the size of a sesame seed.
Researchers at the University of Maine have discovered that planktonic baby lobsters, or larvae, preferentially feed on Calanus finmarchicus, a tiny, calorie-rich zooplankton species, during one of the most vulnerable stages of their lives. Their new study upholds a theory advanced by scientists in the past decade, and one that may be relevant to recent declines in Maine鈥檚 lobster harvest.
Scientists have also observed declines in both the availability of this key food source and the number of young lobsters surviving into adulthood in the Gulf of Maine.
For lobster, the larval stage is a crucial development bottleneck that determines their survival to adulthood. While many researchers have looked at the role of egg production as the main determinant of the size of upcoming harvests, a 91福利-led team has been working to provide more insight into how diet determines whether larvae survive into adulthood.
“We see evidence that larvae are eating Calanus finmarchicus at a greater rate than you would expect if they were just feeding randomly, however we also know that the geographic range of Calanus is receding northward into cooler waters, making it less readily available,” said Alex Ascher, lead research scientist at Quahog Bay Conservancy, who began this work with 91福利 as part of his Ph.D. thesis.
Calanus finmarchicus provides lobster larvae with fatty acids that are energy rich and beneficial for neural development during periods of rapid growth. Researchers from 91福利, Bigelow Laboratory of Ocean Sciences and the University of Southern Maine found that 30% of larval and post-larval lobsters sampled had traces of Calanus finmarchicus, whereas this species comprised only a few percent of the available zooplankton.
The decline in this key food source at the southern end of its range in North Atlantic ecosystems is occurring while fewer lobster larvae in the Gulf of Maine are surviving into adolescence, which in turn impacts the future number of adult lobsters available to the fishery. Maine鈥檚 lobster harvest has declined by about 40% since its peak in 2016, according to the state鈥檚 Department of Marine Resources.
After hatching from eggs on the ocean floor, larvae swim up to the ocean surface. They then drift with currents before settling to the seabed as small juveniles, eventually to become adults some 6-8 years later. Access to nutritious food during the planktonic larval stages can mean the difference between survival and starvation.
These findings also further solidify Calanus finmarchicus as a keystone species, an organism that plays a crucial role in supporting a food chain that includes a diversity of fish and invertebrates, including the endangered North Atlantic right whale. With less energy-rich food availability, lobster larvae have to depend on less nutritious resources, threatening their chance of survival.
Stage one larvae are the most vulnerable, as they are more likely to succumb to starvation compared to older larvae.
“Understanding these larval diets is a fundamental piece of knowledge that helps us to better understand fluctuations, and potentially also predict fluctuations, in the abundance of lobster larvae and future adult lobsters to be caught,” said Ascher.
Ascher is part of a collective effort across Maine and New Hampshire to use new molecular methods to examine larval lobster feeding ecology, including the role of food limitation and the specific impact of Calanus finmarchicus. He collaborated with now retired 91福利 marine sciences professor Richard Wahle, Bigelow Laboratory senior research scientists Peter Countway and David Fields, and Rachel Lasley-Rasher of the University of Southern Maine on his latest study.
To identify what lobster larvae were eating, researchers combined two approaches. They first inspected the stomach contents of lobster samples by traditional methods under a microscope. While this approach is very common in diet studies, the squishier organisms without hard parts the lobster consumed cannot always be identified with a microscope alone.
That is why Ascher also examined genetic samples known as environmental DNA (eDNA), allowing him to pinpoint food sources he couldn鈥檛 visually discern from the larval stomach contents.
“Combining the two approaches allows us to ground truth visual identifications by comparing them to diet identifications from the eDNA analysis, giving us greater certainty and expanding our coverage,” said Ascher.
The team’s findings were recently published in the open-access journal .
Ascher began the study as part of his Ph.D. thesis completed in 2023 under the Maine eDNA research initiative led by 91福利, which engaged other research and education institutions throughout the state and was funded through the National Science Foundation’s Established Program to Stimulate Competitive Research (EPSCoR).
Story by Heather Johnson, EPSCoR Communications Graduate Assistant
Contact :Daniel Timmermann, daniel.timmermann@maine.edu
