A side note to Shawn's post on electrofishing limits and gaps. The equipment is usually depth limited. Thus there are many variables to what a shock survey reveals and how to interpret the data. Come hear Dave Willis go over electrofishing at the Conference.

Also WRT Greg's comments I agree if you can isolate all the variables to conductivity or keep them static (steady) except alkalinity (either by test or experience) the remaining variance is most likely a reflection of alkalinity. But I don't know how to quantify , measure or extrapolate alkalinity from TDS or conductivity.