Changes in Oxygen Consumption of Mottled Sculpin (Cottus bairdii) in Response to Elevated Suspended Sediment Levels

Increasing sedimentation of streams in and around agricultural areas has been observed in conjunction with the production of biofuels. This increase in sediment is largely thought to have a negative impact on the organisms inhabiting these streams. We measured oxygen consumption by mottled sculpin (Cottus bairdii) to determine how this relatively common stream species responds to elevated suspended sediment levels.  We used custom respirometers to monitor oxygen consumption by fish during 3.5 hour trials. Fish <5 g were exposed to sediment levels of 0 (control), 1.00, 1.75, 2.50, and 5.00 g/L, while fish >5 g were exposed to sediment levels of 0 (control) and 1.0 g/L.  Our results indicated that mean oxygen consumption of small mottled sculpin (<5 g) was significantly higher when the fish were exposed to sediment. Oxygen consumption increased when sediment concentrations equaled 1.00 and 1.75 g/L, but did not increase significantly at levels greater than 1.75 g/L. This suggests that mottled sculpin may decrease their metabolism when they reach a threshold concentration of sediment, which would help prevent damage to their gills. While this strategy would work well over short duration exposures, chronic exposure to suspended sediment would likely lead to decreased fitness of individuals in streams impacted by increased levels of human land use.