Vertical Swim Speeds and Habitat Use of Atlantic Tarpon Inferred from Pop-up Archival Transmitting Tags

We evaluated vertical depth and thermal habitat utilization of Atlantic tarpon (Megalops atlanticus) from high-resolution temporal data on 42 recovered Pop-up Archival Transmitting (PAT) tags deployed and recovered from 2002 to 2010 to estimate vertical movement (swim speeds) rates during descents and ascents  All individuals exhibited a strong preference for near-surface depths, spending >80% of their time in water depths < 10 m.  Diel vertical distributions were described by four basic patterns, but there was substantial variation within and among individuals.  Uncommon deep-diving behaviors were apparently associated with spawning activity.  The most preferred water temperatures were around 26 ^oC during the spring and fall migratory periods, but reached > 29 ^oC in summer when tarpon were on their feeding grounds at the northern extreme of their range.  Vertical descent and ascent rates defined as changes in depths extending ≥ 2 m over time were used to estimate from tag data with 1-sec sampling intervals.  Descent rates ranged from 0.01 to 2.74 m s^-1, while ascent rates ranged from 0.01 to 4.5 m s^-1.  Peaks of “rolling and jumping” behaviors inferred from wet/dry sensor data occurred with greatest frequency just after sunset and sunrise.