Vertical movement rates and habitat use of Atlantic tarpon

Abstract

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 rates (swim speeds) during descents and ascents. All individuals strongly preferred shallow waters, spending >80% of their time in water depths <10 m. Diel vertical distributions followed 4 patterns, but there was substantial variation within and among individuals. Vertical descent and ascent rates, defined as changes in depths extending ≥2 m over time, were estimated from tag data with 1 s 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. Relatively uncommon deep diving behaviors might be associated with spawning activity. The most preferred water temperature was ~26°C, particularly during the spring and fall migratory periods. However, these reached >29°C in summer when tarpon were at their feeding grounds at the northern extreme of their range. Peaks of 'rolling and jumping' behaviors inferred from relative conductivity sensor data occurred with greatest frequency just after sunset and sunrise. © Inter-Research 2012.