Warm water temperatures (≥ 20oC) as a threat to adult Pacific lamprey: Implications of climate change

Interest in the effects of warmwater temperatures (≥ 20oC) on fishes has grown as biologists attempt to understand the impacts of climate change on native species. Clemens et al. (2016) hypothesized that rivers displaying warmwater temperatures and low river flows (such as may become more common with climate change in North America) may select against Pacific lamprey Entosphenus tridentatus migrating and spawning in the upper reaches of some watersheds. I provide new information from different locations that supports Clemens et al.’s hypothesis, including observations of pre-spawn mortalities of Pacific lamprey during a recent heat wave, when daily water temperatures averaged 26.6oC (range: 20.8o – 30.6oC) and additional data from the literature. These observations and data suggest that the continued warming and slowing of rivers pose a threat to Pacific lamprey in some Oregon (USA) rivers, which appears to agree with other research that suggests that lampreys will lose habitats in lower latitudes as climate change progresses.