In situ observations of juvenile Sea Lampreys in the Gulf of Maine from a noninvasive trawl survey

Objective This project aimed to document in situ observations of juvenile Sea Lampreys Petromyzon marinus in the Gulf of Maine using noninvasive optical survey technology and to highlight the potential of this method to help address knowledge gaps in their marine distribution, habitat use, and host associations. Methods From 2019 to 2024, a semi-annual (January and May), stratified random, noninvasive optical trawl survey was conducted in the western Gulf of Maine. Video footage was manually reviewed to identify and record occurrences of Sea Lampreys, their host species, depth, and temperature. Results In total, 46 juvenile Sea Lampreys were observed, 45 of which were attached to fish hosts. Most observations occurred during winter surveys (n = 45). Atlantic Mackerel Scomber scombrus (n = 40) were the most common host, followed by Atlantic Herring Clupea harengus (n = 3), Haddock Melanogrammus aeglefinus (n = 1), and Pollock Pollachius virens (n = 1). Observations were made at depths ranging from 32 to 133 m and at temperatures ranging from 5.1°C to 8.3°C. Conclusions These preliminary in situ observations demonstrate the utility of noninvasive optical surveys for studying the poorly understood marine phase of Sea Lampreys. This technology offers new opportunities to investigate lamprey behavior, habitat preferences, and host interactions.