Physiological effects of capturing Kemp's ridley sea turtles, Lepidochelys kempii, in entanglement nets

Abstract

Blood samples were collected from 58 wild Kemp's ridley sea turtles (Lepidochelys kempii) to examine the physiological effects of capture in entanglement nets. Captured turtles were placed in holding tanks or in-water cages to examine whether the postcapture holding protocol influenced the time course of recovery of blood homeostasis. Lactate concentrations at capture were 4.5 ± 0.3 and 3.5 ± 0.3 mmol/L (mean ± SE) for L. kempii assigned to the in-water-cage and holding-tank treatments, respectively. Turtles held in holding tanks for 1 h exhibited a significant increase in lactate concentration over capture levels, whereas lactate concentrations in the cage-held animals did not change. Lactate concentrations declined to less than 1.0 mmol/L by 6 and 10 h post capture for turtles in the in-water-cage and holding-tank treatments, respectively. Plasma norepinephrine (NE) and epinephrine (E) concentrations at capture were substantially elevated above base-line levels reported in the literature for comparably sized loggerhead sea turtles (Caretta caretta). Turtles in holding tanks exhibited greater reductions in NE and E at 1 h post capture than did their counterparts in the in-water cages. Although plasma Na+ and Cl- concentrations were not affected by entanglement netting, K+ concentration was elevated in tank-held L. kempii at 1 h post capture. Taken together, these data indicate that entanglement netting causes significant physiological disturbance in sea turtles and that recovery of blood homeostasis is influenced by the postcapture holding protocol.

Blood Biochemistry of Sea Turtles Captured in Gillnets in the Lower Cape Fear River, North Carolina, USA

“…We found that longer entanglement times resulted in pronounced disruptions in blood biochemistry and were associated with lower physical grades (Tables 1 and 2). In general, blood parameters that did not vary significantly with increased gillnet entanglement time fell within the range of published values for healthy, wild-caught green sea turtles (Bolten and Bjorndal 1992, Aguirre et al 1995, Hasbún et al 1998, whereas parameters that were significantly impacted by gillnet entanglement time were in agreement with literature values for sea turtles exposed to stressors (Lutz and Dunbar-Cooper 1987, Gregory et al 1996, Hoopes et al 2000, Jessop et al 2002, Harms et al 2003.…”

“…Entanglement times of as little as 30 minutes resulted in elevated plasma lactate. The highest lactate value recorded in our study (50.6 mmol/L) was 2-8 times higher than maximum values for blood lactate reported in other studies of sea turtle entanglement in fishing gear (6.2-20 mmol/L; Lutz and Dunbar-Cooper 1987, Hoopes et al 2000, Harms et al 2003. The average blood lactate concentration for green turtles in our study (30.6 6 10.2, n 5 12) was 9 times higher than average blood lactate concentration of rehabilitated captive green turtles not exposed to a stress protocol and just prior to release (3.4 6 1.1, n 5 10; C. Harms, NC State University Center for Marine Sciences and Technology, and J. Beasley, Karen Beasley Sea Turtle Rescue and Rehabilitation Center, unpublished data).…”

“…For example, a significant increase in blood K + concentration has been observed following capture and restraint in Kemp's ridley turtles (Stabenau et al 1991, Hoopes et al 2000. It is possible that K + ions are released by cells in exchange for H + ions to buffer changes in blood pH, although a K + -H + exchanger has not yet been identified in the cells of sea turtles (Rose 1977, Lutz 1997, Hoopes et al 2000, Stabenau and Vietti 2003. It is likely that the acidosis experienced by forcibly submerged sea turtles has both a respiratory and metabolic component.…”

“…Stabenau et al (1991) saw a 6-fold increase in lactate levels of Kemp's ridleys forcibly submerged in shrimp trawls for approximately 7.3 minutes. Kemp's ridley turtles captured in entanglement nets and temporarily restrained in holding tanks also experienced an increase in plasma lactate concentrations and alterations in blood ions indicative of acid-base adjustments (Hoopes et al 2000). Increases in blood lactate concentrations and a concomitant decrease in blood pH suggest a shift towards reliance on anaerobic metabolic pathways, which could be the result of intense activity associated with escape attempts or hypoxia due to forced submergence.…”

Movements and post-release mortality of juvenile sea turtles released from gillnets in the lower Cape Fear River, North Carolina, USA

“…In response to a decrease in blood pH, cells may release K + into the bloodstream in exchange for H + ions. A K + -H + exchanger has been proposed as a buffering mechanism to counteract blood acidosis in sea turtles (Rose 1977, Lutz 1997, Stabenau & Vietti 2003, Hoopes et al 2000, but the membrane proteins that may serve this function have not yet been identified in the cells of sea turtles. Increased plasma Cl -may reflect increased activity of the chloride shift mechanism of red blood cells in response to respiratory acidosis.…”