EFFECTS OF TEMPERATURE, SALINITY, AND SUSPENDED SOLIDS ON THE EARLY LIFE HISTORY STAGES OF ARKANSAS RIVER SHINER

Arkansas River shiner (ARS) Notropis girardi is a federally-threatened cyprinid native to rivers and streams of the Arkansas River Basin. It is a member of a reproductive guild of pelagic broadcast-spawning cyprinids that release non-adhesive, semi-buoyant eggs during an extended spawning season. For successful reproduction, ARS eggs require a combination of sufficient current velocity to remain suspended in the water column and substantial lengths of free-flowing rivers for successful reproduction. Environmental factors such as temperature, total dissolved solids, and total suspended solids have the potential to influence egg buoyancy and developmental rate, thereby affecting the minimal current velocity and stream fragment length required to support ARS populations. However, how environmental factors and fragmentation interact to affect ARS reproductive success is still unclear. I assessed the effects temperature, total dissolved solids, and total suspended solids have on the developmental rate of ARS early life-history stages and the minimal current velocity needed for ARS eggs to remain suspended within a water column. Results show that developmental rate of ARS eggs and larvae were positively correlated with increases in temperature. Eggs incubating in the highest total suspended solid and total dissolved solid treatments developed at a faster rate than counterparts developing at the same temperature but with lower levels of total suspended solids and total dissolved solids. Temperature was negatively correlated and total suspended solids were positively correlated with the minimum current velocity needed to keep ARS eggs in suspension. Together they explained 42% of the variation in current velocity for this experiment. Also, total dissolved solids had no effect on the current velocity and treatments with the highest total suspended solids required the highest flow velocities. The first 24 ̶ 48 hr free-float period for eggs of ARS and other pelagic broadcast-spawning cyprinid is crucial for growth and development. However, if at any point during this time they experience current velocities lower than what has been recorded in my results eggs could sink to the bottom leading to unsuccessful reproduction. More importantly, as the Great Plains ecoregion experiences changes due to both climate and land, use these results could help predict stream reaches capable of sustaining their early life-history strategies.