EVALUATING TECHNIQUES FOR SAMPLING STREAM CRAYFISH (PARANEPHROPS PLANIFRONS)

We evaluated several capture and analysis techniques for estimating ab undance and size structure of freshwater crayfish (Paranephrops planif rons) (koura) from a forested North Island, New Zealand stream to prov ide a methodological basis for future population studies. Direct obser vation at night and collecting with baited traps were not considered u seful. A quadrat sampler was highly biased toward collecting small ind ividuals. Handnetting at night and estimating abundances using the dep letion method were not as efficient as handnetting on different dates and analysing by a mark-recapture technique. Electrofishing was effect ive in collecting koura from different habitats and resulted in the hi ghest abundance estimates, and mark-recapture estimates appeared to be more precise than depletion estimates, especially if multiple recaptu res were made. Handnetting captured more large crayfish relative to el ectrofishing or the quadrat sampler.