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 internesting intervals remained in the vicinity of the upper Texas coast and, upon entering the postnesting 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 northwestern 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 northwestern 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 seasonal in-water distributions, abundances, population dynamics, and mortality risks to all life history stages.

Sea Turtles of the Gulf of Mexico

“…The vast majority of Kemp's ridley nesting occurs on beaches in the western Gulf (Figure 11.10), and most juveniles spend time in the Gulf of Mexico oceanic zone after they leave the beach as hatchlings (Collard and Ogren 1990;TEWG 2000;Putman et al 2010). After the oceanic juvenile stage, juveniles recruit into the neritic zone (inshore marine environment), mostly along the Gulf continental shelf but also along the U.S. Atlantic Coast (Pritchard 1969;Ogren 1989;Schmid 1998;Witzell and Schmid 2004;Seney and Landry 2011), where they continue to feed and grow for a number of years until reaching sexual maturity. Oceanic juveniles that end up in the currents of the Atlantic Ocean move into coastal habitats along the east coast of the United States from Florida to New England, and as far north as the Grand Banks and Nova Scotia (Pritchard 1969;Ogren 1989;Morreale and Standora 1999;Watson et al 2004;Morreale et al 2007;Frazier et al 2007;Landry and Seney 2008).…”

“…Data from capture-markrecapture (CMR) and satellite telemetry studies in the Gulf of Mexico have documented that juvenile turtles leave the coastal foraging areas in the fall and move to more suitable overwintering habitat in deeper or more southern waters and return to the same coastal feeding areas the following spring (Ogren 1989;Schmid 1998;Witzell and Schmid 2004;Landry et al 2005;Barichivich 2005, 2006;Renaud and Williams 2005;Schmid and Witzell 2006;Seney and Landry 2011). For example, Renaud and Williams (2005) documented the fall and winter movements of Kemp's ridleys in the Gulf of Mexico in response to changing seawater temperature using satellite telemetry.…”

“…In a related satellite telemetry study, the inshore and continental shelf waters of the northwestern Gulf of Mexico were shown to serve as developmental and migratory habitat for the Kemp's ridley sea turtle (Seney and Landry 2011). Fifteen juveniles were fitted with transmitters and released off the upper Texas coast from 2004 through 2007.…”

“…Fifteen juveniles were fitted with transmitters and released off the upper Texas coast from 2004 through 2007. Their movements were restricted to the continental shelf from Matagorda Bay, Texas, east to waters offshore Timbalier Bay, Louisiana, and during most or all of the tracking period, the juveniles remained primarily in waters less than 5 m (16.4 ft) deep (Seney and Landry 2011). While movement patterns varied among years, the juvenile Kemp's ridleys were tracked primarily during the warmer months and preferred tidal passes, bays, coastal lakes, and nearshore waters.…”

Using an ocean model to predict likely drift tracks of sea turtle carcasses in the north central Gulf of Mexico

“…Satellite-tagged Kemp's ridley sea turtles have been observed occupying near shore waters from Texas to the Florida Keys, with a 'hotspot' located from south Texas to the Florida panhandle (Shaver & Rubio 2008). This area contains abundant crab and shrimp populations and appears to be a primary foraging area for juvenile Kemp's ridley sea turtles (Shaver & Rubio 2008, Seney & Landry 2011, Lyn et al 2012.…”