1. Climate Projections and Pacific Lamprey Conservation: Evidence That Larvae in Natural Conditions May Be Resilient to Climate Warming.
- Author
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Whitesel, Timothy A. and Sankovich, Paul M.
- Subjects
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GLOBAL warming , *WATER temperature , *FIELD research , *ATMOSPHERIC models , *LAMPREYS - Abstract
Simple Summary: Climate models suggest that by the year 2100, maximum stream temperatures may approach 27–31 °C in areas where larval Pacific lampreys currently rear. Whether larval Pacific lampreys in natural environments can tolerate these temperatures is unknown. We combined laboratory studies with field surveys to evaluate whether larvae in natural conditions have this ability. In a laboratory setting, some larvae were able to survive days when the maximum temperature reached 33.6 °C. The results also indicated that most larvae may be able to tolerate days when maximum temperatures reach 30.8–32.0 °C. During three years of field surveys, we observed larvae in warm areas where maximum temperatures during the day ranged from 27.7 to 33.9 °C. Our ability to find larvae in areas that were warm, and at times when they were warm, was similar to our ability to find larvae in areas that were relatively cool and at times when areas were not warm. These findings suggest larval Pacific lampreys in natural environments may be resilient to climate warming. However, it is unclear whether warming temperatures may harm larval Pacific lampreys without causing them to die. In many areas where larval Pacific lampreys currently rear, maximum stream temperatures may approach 27–31 °C during the next 75 years. Whether larval Pacific lampreys in natural conditions can tolerate these temperatures is unknown. To evaluate this ability, we conducted Direct Acute Exposure (DAE) experiments using simulated natural daily temperature (SNT) cycles in the laboratory and occupancy surveys in the Umatilla River (river). When evaluated relative to daily maximum temperatures, after seven days in DAE experiments, 78–100% of larvae survived in 29.1 °C, only larvae acclimated to 26.8 °C survived in 31.0 °C, and no larvae survived in 33.6 °C. Based on daily maximum temperatures, the ultimate upper incipient lethal temperature was estimated to be >30.8 °C using a time to death analysis and >32.0 °C using a percent mortality analysis. Some larvae acclimated to 31.0 °C were also able to survive four consecutive days with a daily maximum temperature of 33.6 °C. In 2018–2020, warm areas of the river experienced maximum temperatures in July and August that ranged from 27.7 to 33.9 °C, while cool areas experienced maximum temperatures <27.7 °C. Before, during and after the period of maximum temperatures each year, larvae occupied both areas. Detection probabilities ranged from 0.83 to 1.00 and were similar for each area and for all survey periods. This work suggests that ectothermic, larval Pacific lampreys in natural environments may be resilient to the water temperatures that are likely to result from climate warming. It is unclear whether relatively high but sublethal temperatures may impact the behavior, and ultimately survival, of larval Pacific lampreys. [ABSTRACT FROM AUTHOR]
- Published
- 2025
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