Stellwagen Mapping Initiative

The Stellwagen Mapping Initiative is a multi-year collaborative project to explore and survey the seafloor in Stellwagen Bank National Marine Sanctuary for underwater cultural heritage sites, such as shipwrecks, using the latest in side-scan sonar technology. This innovative mapping initiative brings together scientists, engineers, sanctuary staff, and the fishing industry. Through this initiative, NOAA hires local fishermen and their vessels as a work platform to tow side-scan sonar (a "towfish") under the guidance of a locally-contracted sonar team. The work relies on fishermen's local knowledge of sanctuary waters to enable focused, efficient exploration that helps researchers gather important maritime heritage data while also informing the fishing community of potential underwater hazards to avoid.

The National Marine Sanctuary Foundation acts as a nonprofit partner, helping to connect all involved parties.

Of the estimated 200+ shipwrecks within Stellwagen Bank National Marine Sanctuary, only 47 had been discovered prior to the launch of this public-private mapping initiative, and only 18% of the sanctuary had been surveyed with high-resolution side-scan sonar. In addition to discovering underwater cultural heritage throughout the sanctuary, the project also surveys previously documented shipwrecks and cultural heritage resources and assesses the performance of protection measures.

Knowing Where to Look

To determine potential areas with underwater cultural heritage resources, our researchers collaborate with industry partners to gather thousands of locations where fishermen have snagged their nets on underwater obstructions, known as "hangs". In order to focus on the obstructions most likely to contain underwater cultural heritage resources, these locations are analyzed using custom algorithms that rely on machine learning. Once survey locations are determined, the team develops survey plans that the fishing vessel and towfish will follow to collect sonar data. The captains then "mow the lawn", following tracklines and imaging wide swaths of the bottom of Stellwagen Bank National Marine Sanctuary.

Researchers then use the resulting acoustic data to compile mosaic imagery of the bottom and interpret the data to identify features of interest. Once a significant item of underwater cultural heritage is acoustically imaged, its location, size and description are logged for investigation by a remotely-operated vehicle (ROV) or diver. The team uses these findings in conjunction with historical research and fishing community knowledge, with the objective of sharing and educating the public and stakeholders on the collective research and discoveries.

Exceeding Expectations

This project has demonstrated remarkable success. In the first year of operations, the team's goal was to locate at least one previously-undiscovered underwater cultural heritage site, and through the collaborative model described above, they located six potential shipwreck sites! In addition, they located marine debris, known as derelict commercial fishing gear, which continues to harm sea life and poses an obstruction to fishermen. They also found unexploded ordnance, on their October 2024 trip near the southwest corner of Stellwagen Bank by a location provided by a local fisherman. Based on the imagery, the ordnance is possibly USN Mk 6 Depth Charge.

The Stellwagen Mapping Initiative embodies the value of NOAA's partnerships with the local fishing industry, as well as improving scientific methods with local experts for underwater exploration. As it grows, the collaboration will continue to increase on-the-job safety for fishermen in the region. Monitoring the condition of shipwrecks over time also provides scientists with unique vantage points for underwater ecosystems as well as feedback on sanctuary protection measures. UCH offers educational and scientific opportunities, helping us better remember and understand our history and these special underwater places.

Email [email protected] with the subject "Stellwagen Mapping Initiative" or "SMI" to get involved!