Movement patterns of immature and adult female Kemp’s ridley sea turtles in the northwestern Gulf of Mexico

Abstract

The Kemp's ridley sea turtle Lepidochelys kempii is recovering from declines that reduced nesting from a single-day estimate of 10 000 to 40 000 females in 1947 to <300 during the entire 1985 nesting season. Although beach monitoring is crucial to estimating nesting population size and activity, in-water data are essential for understanding population dynamics, evaluating management strategies, and ensuring the species' continued recovery. Fifteen immature and 7 adult female ridleys were fitted with platform terminal transmitters and released off the upper Texas coast during 2004 through 2007. Immature individuals were tracked primarily during warmer months and exhibited preferences for tidal passes, bays, coastal lakes, and nearshore waters, although movement patterns varied among years. Females tracked during their inter- nesting intervals remained in the vicinity of the upper Texas coast and, upon entering the post- nesting stage, moved eastward along the 20 m isobath to foraging areas offshore of central Louisiana. Satellite telemetry indicated that inshore and continental shelf waters of the northwest- ern Gulf of Mexico serve as developmental, migratory, inter-nesting, and post-nesting habitat for the Kemp's ridley. Projected population growth will likely lead to increased use of the northwest- ern Gulf by the species and more frequent encounters with human activities. The extent of such anthropogenic interactions and need for mitigation measures should be examined and considered by natural resource managers to facilitate continued recovery of this and other sea turtle species in the Gulf of Mexico. Likewise, research efforts should be continued to better understand sea- sonal in-water distributions, abundances, population dynamics, and mortality risks to all life his- tory stages.