Individual variation and repeatability of Atlantic tarpon Megalops atlanticus migrations in the southern US: implications for conservation and management

Individual fish movement patterns and behaviors influence population-level traits, and are important for understanding their ecology and evolution. Understanding these behaviors is key for managing and conserving migratory animal populations, including Atlantic tarpon ( Megalops atlanticus ), that support an economically important recreational fishery. Using acoustic telemetry, we tracked individual movement patterns of M. atlanticus inhabiting the eastern Gulf of Mexico and the southeast coast of the US over successive years. Net-squared displacement models revealed considerable individual-level variation in movement patterns with high individual-level repeatability in the timing of migrations and migratory pathways. Although distinct migratory subgroups existed, M. atlanticus generally migrate northward in the spring and summer to putative foraging grounds and remain in these areas for, on average, four months and then migrate southward in the fall. Subadult M. atlanticus exhibited similar migratory patterns as adults, while large juveniles exhibited either resident or nomadic behaviors. For migratory individuals, fish size did not influence movement patterns. Given that distinct migratory subgroups seasonally mixed in southern Florida for spawning activity, our study indicates that M. atlanticus along the eastern Gulf of Mexico and southeastern coast of the US should be considered a single interconnected stock. With that in mind, using M. atlanticus angler and guide knowledge, we assessed the vulnerability of M. atlanticus to potential threats across their range and along migratory pathways. Collectively, the far-ranging nature of M. atlanticus and their diversity in movement patterns highlights the need for more uniform and cohesive management and conservation efforts.