Effects of total suspended sediment on survival of Yaqui chub eggs and larvae

Authors: Stephani L. Clark Barkalow, Scott A. Bonar

Year: 2013 (xlv)

Abstract

The effects of total suspended sediment (TSS) on Yaqui chub, Gila purpurea, are unknown, but the effects have been studied on other fish species; increases in TSS have been shown to change food supply, food acquisition by fish, and disrupt reproductive efforts. We installed 32 Nalgene stormwater samplers to collect water during flood events in Black Draw and analyzed the samples for TSS concentration to document the range of sediment levels in the drainage. TSS concentrations range from 3.0mg/L to 67340.4mg/L. We exposed Yaqui chub eggs and larvae to levels of TSS found in Black Draw in sediment suspension aquaria consisting of a 5 gallon container with a propeller to suspend sediment, collected from Black Draw. Each treatment lasted for 11 days, the duration of the longest flood event in 2011 or until all fish or eggs were deceased. At the end of the treatment period, we quantified the hatch rates for egg and survival rates for larval fish. We computed an LC50, the median lethal concentration of sediment, for both the larval and egg trials. Yaqui chub eggs were negatively impacted by TSS of greater than 5000mg/L. Testing of different sediment concentrations allows evaluation of effects of sediment on sensitive life stages of Yaqui chub. This can aid managers by identifying lethal levels of sediment so that sediment can be managed for survival of sensitive life stages.