Cf. Rabeni et al., EVALUATING TECHNIQUES FOR SAMPLING STREAM CRAYFISH (PARANEPHROPS PLANIFRONS), New Zealand Journal of Marine and Freshwater Research, 31(5), 1997, pp. 693-700
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.