An evaluation of potential climate change impacts on the larval metamorphosis of Pacific Lamprey (Entosphenus tridentatus)

Larval Pacific Lamprey must undergo metamorphosis to reproduce. Physiological and environmental factors appear to impact when this metamorphosis occurs. In other lamprey species, larvae that reach a certain threshold for energy storage appear to initiate metamorphosis when exposed to cold winter water temperatures followed by a rise in spring water temperatures. Since climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.

Learn more about climate change driven increases in minimum winter water temperatures may affect the magnitude of this seasonal rise in temperatures, there is concern this might affect the rate of metamorphosis for larval Pacific Lamprey. Therefore, we conducted a laboratory study that examined rates of metamorphosis between lamprey experiencing natural winter water temperatures, and those who were exposed to minimum winter water temperatures that were truncated and prevented from falling below approximately 9°C. Larval Pacific Lamprey were collected (N = 90) and used for the experiment whose length and weight suggested that they were likely to transform in the autumn or winter of the following year. There was no significant difference between the rate of metamorphosis between fish exposed to natural water temperatures (37%) and warmed minimum water temperatures (43%), suggesting that changes in the magnitude of winter water temperatures may not have direct negative effects on the metamorphic rates of larval Pacific Lamprey. Our selective collection of larval Pacific Lamprey based on length and weight relationships resulted in relatively high metamorphic rates for reared fish compared to rates observed in other larval lamprey collections. Larvae that did not undergo metamorphosis in the autumn were of a size that models predict will undergo transformation in the following year. A new cohort of collected larvae, and fish from the original larval cohort that did not undergo metamorphosis, will be reared the following year to see if these results are repeatable and to examine if large larvae from the original cohort will transform.