A quick method of determining rock surface area for quantification of the invertebrate community

Stone and rock substrates provide important habitat for many types of strea m-dwelling invertebrates. Measures of the invertebrate communities inhabiti ng rock substrates are often an important component of ecological, monitori ng and disturbance studies in streams. A major obstacle to researchers exam ining rock-inhabiting invertebrates is the time and effort expended on curr ently used methods of determining rock surface area to derive invertebrate densities on these substrates. In an attempt to more efficiently determine invertebrate densities from rock substrates in streams, we tested a direct method of calculating rock surface area from rock weight or displacement vo lume. This method allows very quick determinations of rock surface area in the field. Surface area estimates made using this technique were highly cor related to those from a widely used and more time-consuming method. Measure ments made using this new method should theoretically give better surface a rea estimates than any other commonly used technique.