Multi-year migrations of four coastal shark species in the southeastern USA: trends in timing and temperature

The migrations of many coastal sharks, while often influenced by ocean temperature, remain poorly defined, limiting the ability to plan for changes in stock distribution and habitat quality as oceans warm. This study leverages regional-scale acoustic telemetry networks to document the timing and sea surface temperature (SST) associated with annual migrations of blacknose sharks Carcharhinus acronotus , finetooth sharks C. isodon , lemon sharks Negaprion brevirostris , and Atlantic sharpnose sharks Rhizoprionodon terraenovae along the US southeast coast. From 2010 to 2022, 201 sharks were tracked for an average of 3.2 yr (max 7.4 yr), with 1676 migratory movements observed between widely spaced acoustic receiver arrays. Blacknose, finetooth, and lemon sharks overwintered primarily off east-central Florida and spent spring through fall in coastal waters from northeast Florida through the Carolinas. In contrast, sharpnose sharks dispersed widely in winter but commonly migrated south into east Florida by summer. Lemon sharks were observed at the lowest SST and sharpnose sharks at the highest, with sharks generally experiencing cooler temperatures when migrating north vs. south. Boosted regression tree modeling confirmed that SST consistently helped explain seasonal arrivals along the Florida and Georgia coasts, although changes in SST and daylength were also important depending on species and location. For all species, migrations were seasonal expansions and contractions of geographic range as opposed to shifts in the center of the tagged population. These findings will help benchmark future shifts in migration patterns as oceans continue to warm and will simplify comparisons with the migration behavior of other sympatric shark species.