Cooperative Fish and Wildlife Research Units Program: Hawaii
Education, Research and Technical Assistance for Managing Our Natural Resources

Seasonal movements cued by environmental variables are a critical component of riverine fish life-history. Life history events for species such as blue sucker Cycleptus elongatus are likely cued by discharge and temperature and may be disrupted if those life-history events and environmental regimes are mismatched. However, this effect may be dependent upon habitat occupied when environmental cues are received by individuals. We tracked telemetered blue sucker in the Colorado River, Texas, USA from 2015-2017 and modeled the relative effects of discharge, temperature, and habitat structure on seasonal movement patterns. Tagged fish varied in their propensity to move, though most returned to original tagging locations. Decreasing temperatures and increasing discharge resulted in increased seasonal movements. Temperature and discharge had the largest effect on movement behavior but the magnitude of movements was largely dependent on year. Temperatures between 12-19 °C and discharges between 10-240 m³s^-1 resulted in greater probabilities of spawning movements. Spawning was most probable in 2015 and reduced or halted in 2016 and 2017. Future climate scenarios suggest North America will experience increased drought, warmer temperatures, and more variable weather patterns. These future scenarios could negatively impact blue sucker by disrupting environmental cues and habitat availability for seasonal life-history events. Our results suggest temperature and discharge are critical cues for the species, but that their combined effect is largely dependent on occupied habitat.