Upper temperature limit of larval Pacific lamprey Entosphenus tridentatus: implications for conservation in a warming climate

Abstract

Climate models suggest that by 2100, maximum temperatures where many larval Pacific lamprey, Entosphenus tridentatus, rear now may approach 27–31 °C. Little information exists on whether larval Pacific lamprey can tolerate these temperatures. We used acclimated chronic exposure (ACE) and direct acute exposure (DAE) experiments to determine the water temperature that is lethal to larval Pacific lamprey and whether sublethal water temperatures influence larval burrowing behavior. After 30 days in ACE experiments, all larvae survived in temperatures averaging ≤ 27.7 °C, no larvae survived in temperatures averaging ≥ 30.7 °C and the ultimate upper incipient lethal temperature (UILT) was estimated to be 29.2 °C. After seven days in DAE experiments, all larvae survived in 27.1 °C, only larvae acclimated to 23.3 °C survived in 29.1 °C, and no larvae survived in temperatures ≥ 30.6 °C. Using a time to death analysis, estimates of the UILTs ranged from 27.5 to 30.2 °C and the ultimate UILT was estimated to be > 28.3 °C. Using a percent mortality analysis, estimates of the ultimate UILT were not definitive but indicated it may be > 30.2 °C. To burrow, larvae reared for 30 days at temperatures averaging 26.9–27.7 °C exhibited more total time, active time, and stops than those reared for 30 days at temperatures averaging 22.3–23.9 °C. Our findings suggest that larval Pacific lamprey may be resilient to the most likely temperature increase scenarios predicted by climate models. However, they may be vulnerable to the high-temperature increase scenarios and, relatively high but sublethal temperatures may impact the behavior, and ultimately survival, of larval Pacific lamprey.

Bringing partners together: A symposium on native lampreys and the Pacific Lamprey Conservation Initiative

“…2020; Wang et al. 2020, 2021; Whitesel and Uh 2023). As a result, research has addressed conservation and management actions to mitigate threats and support lamprey populations through recolonization after barrier removal (e.g., Hogg et al.…”

“…Similarly, the direction of the primary literature on native lampreys has guided the conservation and management of their aquatic habitats. This research has helped us understand the effects of identified threats on native lampreys and their habitats, such as barriers to migration (e.g., Bracken et al 2015;Schultz et al 2016;Jubb et al 2023), contaminants (e.g., Nilsen et al 2015;Linley et al 2016;Madenjian et al 2021), habitat dewatering (e.g., Rodríguez-Lozano et al 2019;Harris et al 2020), and climate change (e.g., Goertler et al 2020;Wang et al 2020Wang et al , 2021Whitesel and Uh 2023). As a result, research has addressed conservation and management actions to mitigate threats and support lamprey populations through recolonization after barrier removal (e.g., Hogg et al 2013;Jolley et al 2018;Hess et al 2021), translocation (e.g., Ward et al 2012;Hess et al 2022), lamprey-specific structures to aid passage (e.g., Moser et al 2011;Frick et al 2017;Lothian et al 2020), and habitat restoration (Roni 2003;Gonzalez et al 2017).…”

Synthesis of larval lamprey responses to dewatering: State of the science, critical uncertainties, and management implications

“…Mortality from exposure to dewatering and the salvage treatment was not more than 6% when mean air temperature was <18°C (mean water temperature ≤12°C), whereas mortality was 20% when mean air temperature was 36°C (mean water temperature = 20°C; Harris et al 2023). Larval lampreys have a high tolerance for changing water temperatures, but temperatures above 18-20°C can cause behavioral effects (e.g., slowed burrowing) and mortality occurs at around 28-30°C (Meeuwig et al 2005;Lampman et al 2021;Whitesel and Uh 2022). Thus, when water temperatures are below 18-20°C, salvage efforts may result in low direct mortality for larval lampreys.…”

“…2005; Lampman et al. 2021; Whitesel and Uh 2022). Thus, when water temperatures are below 18–20°C, salvage efforts may result in low direct mortality for larval lampreys.…”

Thermal refuge use and parasitism: Spatiotemporal variation in anchor worm and lamprey wounds on Klamath redband trout

“…Whether lampreys use thermal refuge is poorly understood. Physiological studies suggest an upper thermal limit of 30°C and an optimum of 15°C (Golovanov et al, 2019; Sankovich & Whitesel, 2019; Whitesel & Uh, 2022) (lethal temperature were only confirmed with ammocoetes), though ontogenetic and population‐level variations add uncertainty. Adult lampreys have been found in UKL in summer, during which temperatures can exceed 25°C (D. Markle and S. Colvin, personal communication).…”