Larvae of the American lobster <i>Homarus americanus</i> H. Milne Edwards, 1837 (Decapoda: Astacidea: Nephropidae) in midcoast Maine USA from 2018–2023: density, seasonality, and carapace lengths

Abstract The planktonic larvae of the American lobster (Homarus americanus H. Milne Edwards, 1837) in the Gulf of Maine typically hatch in the summer and are sensitive to conditions in the water column including temperature, salinity, and prey availability. Their ability to survive at this stage has both ecological and economic impacts to New England states and disproportionately in Maine. While monitoring surveys for all other life stages of lobster have occurred consistently throughout Maine, understanding the density and seasonality of the larval supply has been a persistent data gap for the past two decades due to the difficulty in sustaining a survey over the length of the larval supply season. Our study publishes the first six years of the newest lobster monitoring survey in Maine, which spans four fixed sites in midcoast Maine. We have revisited larval sites last sampled in 2001, added new sites, and expanded the data collected to comprehensively sample density, seasonality, larval carapace lengths, temperature, salinity, and the zooplankton community composition. We document an earlier peak in Stage I larval abundance compared with historical data, explore correlations in how food availability in early stages is related to later stage densities, record multiple peaks in both postlarval densities and fluctuations both seasonally and annually in their carapace lengths, and identify high densities of postlarval lobsters in 2023. We compare the measured density and carapace lengths of larvae with temperature, salinity, and preferred prey items to aid in explaining the patterns documented by this survey. This larval survey is anticipated to continue monitoring efforts and contribute an understanding of larval lobster patterns in the Gulf of Maine.