Large-Scale Environmental Changes May be Responsible for Population Trends of Pacific Lamprey throughout Their Distribution

Abundance of adult Pacific Lamprey Entosphenus tridentatus is highly variable throughout their natural range. We previously used dam counts from the Columbia River, USA to identify significant relationships between population trends and availability of host species in the marine environment. Additional data from northern Russia, Canada, and the USA mirror trends in the Columbia River, while observations from lower latitudes do not (e.g., Oregon, USA). We provide data suggesting that large-scale environmental changes effect Pacific Lamprey populations in both the ocean, during the adult feeding phase, and freshwater, during spawning and early rearing. These relationships also suggest that conditions experienced during early rearing may be increasingly important with decreasing latitude.