Summary of estimates of Kemp’s ridley (<i>Lepidochelys kempii</i>) Straight and Curved Carapace Lengths (SCL and CCL, cm) associated with Size at Sexual Maturation (SSM) and associated Age at Sexual Maturation (ASM) reported in the literature (gray-shaded rows).

<p>Summary of estimates of Kemp’s ridley (<i>Lepidochelys kempii</i>) Straight and Curved Carapace Lengths (SCL and CCL, cm) associated with Size at Sexual Maturation (SSM) and associated Age at Sexual Maturation (ASM) reported in the literature (gray-shaded rows).</p

Logistic curves fit to bootstrapped, back-calculated Gulf of Mexico Kemp’s ridley (<i>Lepidochelys kempii</i>) size and age data.

<p>A. straightline carapace lengths (notch-tip; SCL) and B. age estimates. Model fits predict that 50% of the population would become mature by 61.0 cm SCL and age 13.3 yr.</p

Summary of Generalized Additive Mixed Model (GAMM) graphical output for models incorporating all back-calculated somatic growth data for known-sex Gulf of Mexico Kemp’s ridley sea turtles (<i>Lepidochelys kempii</i>), Straightline Carapace Length (notch-tip; SCL) or age (yr), and calendar year (Year).

<p>Plots for those covariates exhibiting a significant influence on growth response are shown. Solid lines represent mean growth response centered around 0 and dashed lines represent the extent of the 95% Bayesian credible interval. The short, vertical lines above the horizontal axis (i.e., ‘rugs’) represent the distribution of samples for a given covariate. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0173999#pone.0173999.s004" target="_blank">S2 Table</a> for sample sizes and statistical output.</p

Annual somatic growth rate data for 10 cm Straightline Carapace Length (SCL) size classes for Kemp’s ridley sea turtles (<i>Lepidochelys kempii</i>) in the Gulf of Mexico (GOM) and along the US Atlantic coast yielded by skeletochronological analysis and capture-mark-recapture studies.

<p>Annual somatic growth rate data for 10 cm Straightline Carapace Length (SCL) size classes for Kemp’s ridley sea turtles (<i>Lepidochelys kempii</i>) in the Gulf of Mexico (GOM) and along the US Atlantic coast yielded by skeletochronological analysis and capture-mark-recapture studies.</p

Summary of attributes related to reproductive maturation for Gulf of Mexico Kemp’s ridley sea turtles (<i>Lepidochelys kempii</i>), as estimated from the Line of Arrested Growth (LAG) associated with the onset of rapprochement.

<p>Summary of attributes related to reproductive maturation for Gulf of Mexico Kemp’s ridley sea turtles (<i>Lepidochelys kempii</i>), as estimated from the Line of Arrested Growth (LAG) associated with the onset of rapprochement.</p

Comparison of somatic growth for Kemp’s ridleys (<i>Lepidochelys kempii</i>) in the Gulf of Mexico (GOM; white; n = 535) and the Atlantic US coast (ATL; dark gray [13]; n = 178) prior to the year 2000.

<p>A. 10 cm size class-specific back-calculated annual somatic growth rates. Horizontal black lines represent means and bars extending to either side represent 1 SE; B. Faben’s modified von Bertalanffy growth curves where <i>k</i> is the von Bertalanffy growth coefficient. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0173999#pone.0173999.t003" target="_blank">Table 3</a> for additional growth curve parameters.</p

Generalized Additive Mixed Model (GAMM) spline fits (solid line) and 95% confidence intervals (dashed lines) for growth response relative to calendar year for back-calculated annual somatic growth data for Gulf of Mexico Kemp’s ridley sea turtles (<i>Lepidochelys kempii</i>) >50 cm Straightline Carapace Length (SCL).

<p>A. 50–59.9 cm SCL (n = 339). B. 60–69.9 cm SCL (n = 285).</p

Water temperatures at different locations of the study area (full lines) and air temperature at Bob Hall Pier (dashed line) during the period 30 January to 17 February 2011 (UTC), including two of the largest hypothermic stunning events (1–8 February and 10–17 February) of the study period.

<p>Water and air temperatures two days prior to the first event were included for comparison. The bars indicate the chronology of the hypothermic stunned turtles recorded in the Upper Laguna Madre (blue), Lower Laguna Madre (red), Brazos Santiago Pass (orange) and rest of the study area (white).</p

Comparison of the seasonal recording of hypothermic stunned turtles (bars) with winter (November–March) mean water temperatures (full line) and mean water temperature during the two consecutive coldest days of the winters with starting date indicated (diamonds).

<p>Water temperatures are for the Upper Laguna Madre (Bird Island Basin). An approximate threshold of 8.0°C identifies winters with substantial numbers of hypothermic stunned turtles recorded. *Water temperatures were not available for the full 2014–2015 winter.</p

Hypothermic stunning of green sea turtles in a western Gulf of Mexico foraging habitat

<div><p>Texas waters provide one of the most important developmental and foraging habitats for juvenile green turtles (<i>Chelonia mydas</i>) in the western Gulf of Mexico, but hypothermic stunning is a significant threat and was the largest cause of green turtle strandings in Texas from 1980 through 2015; of the 8,107 green turtles found stranded, 4,529 (55.9%) were victims of hypothermic stunning. Additionally, during this time, 203 hypothermic stunned green turtles were found incidentally captured due to power plant water intake entrapment. Overall, 63.9% of 4,529 hypothermic stunned turtles were found alive, and 92.0% of those survived rehabilitation and were released. Numbers of green turtles recorded as stranded and as affected by hypothermic stunning increased over time, and were most numerous from 2007 through 2015. Large hypothermic stunning events (with more than 450 turtles documented) occurred during the winters of 2009–2010, 2010–2011, 2013–2014, and 2014–2015. Hypothermic stunning was documented between November and March, but peaked at various times depending on passage of severe weather systems. Hypothermic stunning occurred state-wide, but was most prevalent in South Texas, particularly the Laguna Madre. In the Laguna Madre, hypothermic stunning was associated with an abrupt drop in water temperatures strong northerly winds, and a threshold mean water temperature of 8.0°C predicted large turtle hypothermic stunning events. Knowledge of environmental parameters contributing to hypothermic stunning and the temporal and spatial distribution of turtles affected in the past, can aid with formulation of proactive, targeted search and rescue efforts that can ultimately save the lives of many affected individuals, and aid with recovery efforts for this bi-national stock. Such rescue efforts are required under the U.S. Endangered Species Act and respond to humanitarian concerns of the public.</p></div