# Not Just Corticosterone: Further Characterization of the Endocrine Response of Kemp’s Ridley Sea Turtles (Lepidochelys kempii) Reveals Elevated Plasma Aldosterone Concentrations During Field Capture Events

## TL;DR

This study shows that capturing Kemp’s ridley sea turtles causes a strong stress response, with high levels of stress hormones like corticosterone and aldosterone, especially when using trawl nets.

## Contribution

The study reveals elevated aldosterone concentrations in Kemp’s ridley sea turtles during capture events, expanding understanding of their stress response beyond corticosterone.

## Key findings

- Turtles captured with trawl nets had significantly higher corticosterone and aldosterone levels than manually captured turtles.
- Aldosterone concentrations were positively correlated with corticosterone after capture.
- Trawl-captured turtles showed higher lactate and potassium levels, indicating greater physical exertion.

## Abstract

To develop safe management policies, it is important to understand the effects of fishing interactions and scientific research on endangered marine species. In this study, concentrations of three important hormones, corticosterone, thyroid hormone, and aldosterone, were determined for 61 healthy, wild Kemp’s ridley sea turtles (Lepidochelys kempii) that were captured for separate scientific studies using two capture methods (a trawl net towed by a boat, 40 turtles; or capture by hand or a hand-held net, 21 turtles). Hormone concentrations were assessed in relation to eight other blood parameters, such as sodium and blood sugar. Corticosterone and aldosterone concentrations were moderately high after capture, with significantly higher concentrations in turtles captured by trawl net vs. manual capture, indicating a substantial stress response. Thyroid hormone concentrations were within previously published ranges for healthy individuals of this species. Other blood data revealed evidence of physical exertion, with some markers of exertion being significantly greater in trawl-captured turtles. The results of this study indicate that captured Kemp’s ridley sea turtles have a robust hormonal stress response, resulting in high plasma concentrations of corticosterone and aldosterone. Researchers who use such methods to access sea turtles can consider these results in planning careful and efficient field studies.

To develop safe and effective management policies, it is important to understand the physiologic effects of fishing interactions and scientific research methods on endangered marine species. In the present study, validated assays for plasma corticosterone, free thyroxine (fT4), and aldosterone were used to assess the endocrine status of 61 presumed healthy, wild Kemp’s ridley sea turtles (Lepidochelys kempii) that were captured for separate ecological studies using two capture methods (trawl net n = 40; manual capture n = 21). Plasma hormone concentrations were also assessed in relation to eight clinical plasma biochemical analytes. Corticosterone and aldosterone concentrations were moderately high after capture, with significantly higher concentrations in turtles captured by trawl net vs. manual capture. Free thyroxine concentrations were within previously published ranges for healthy individuals of this species. Clinical biochemical data revealed moderately elevated potassium and lactate concentrations in many individuals, with significantly greater lactate concentrations in trawl-captured turtles. Aldosterone concentrations were positively correlated with corticosterone. The results of the present study indicate that Kemp’s ridley sea turtles have robust adrenocortical activity immediately after capture, resulting in high plasma concentrations of corticosterone and aldosterone. Researchers who use such methods to access sea turtles can consider these results in planning careful and efficient field studies.