Massachusetts Division of Marine Fisheries (DMF) surveys show continued growth in horseshoe crab populations, thanks to 25 years of coordinated management under the Interstate Fishery Management Plan and stronger state protections.Key survey results:
- DMF Trawl Survey (since 1982): After years of decline, abundance has reversed and reached record highs, especially south of Cape Cod. Spring 2025 saw the highest number of females ever recorded in that region.
- Massachusetts Horseshoe Crab Spawning Beach Survey: Over 300 volunteers surveyed 16 sites in 2025. Ninety percent of sites show increasing trends over the past decade, with several beaches setting new record highs. The strongest gains are in areas with the most commercial harvest, such as Nantucket Sound and Pleasant Bay.
- DMF Seine Survey (since 1984): Counts have stayed above average for 11 straight years. In 2025, the survey recorded the third-highest total in its 42-year history.
These improvements align with regulatory actions. Lunar closures began in 2010, followed by a broader spawning closure in 2024 (April 15–June 7) that protects about 90% of the spawning season. Populations north of Cape Cod remain stable, while the strongest increases are south of the Cape where most harvest occurs.
Horseshoe crabs take 9–11 years to reach maturity, so full benefits of the latest protections will take time. However, recent data already reflect the success of earlier measures…