Sampling stream invertebrates using electroshocking techniques: implications for basic and applied research

We present a new technique using electrofishing equipment to collect and qu antitatively sample stream invertebrates. We used an electrofishing machine with a small anode to produce a localized field of pulsed direct current t o induce invertebrate drift. We quickly obtained large numbers of live inve rtebrates for experiments by passing the anode over the stream bottom upstr eam of sampling nets. We compared the results of five techniques: (i) elect roshocking inside a modified Hess sampler, (ii) repeated electroshocking ov er a large area to estimate population size by depletion, (iii) traditional Surber, (iv) Hess, and (v) individual stone sampling. Electroshocking tech niques provided estimates of invertebrate density comparable with those of traditional sampling techniques. The electroshocking depletion method that sampled a large area provided higher measures of Ephemeroptera, Plecoptera, and Trichoptera richness. Hess and area-restricted electrobug methods had similar density and diversity estimates, whereas the Surber sampler provide d low density estimates, especially for mobile taxa. Density estimates from individual stones were inflated, were biased for mayflies, and had low ric hness. Samples taken with the electroshocking method were processed 40% fas ter because these samples contained little detritus. Electroshocking techni ques can provide accurate estimates of population size and diversity, minim ize disturbance to benthic habitats, and reduce processing time.