Effects of electric fishing on the invertebrate fauna of a New Zealand stream

Electric fishing experiments were made in Woolly Creek, part of the Glenariffe system of tributaries to the Rakaia River, South Island, New Zealand, during December 1972. Two operators electric fished a 25‐m length of stream from the banks, with three runs in both upstream and downstream directions.

Large increases in drift were caused by the electric fishing process, which had a marked effect on the Ephemeroptera and the oligochaete families Tubificidae and Lumbriculidae.

The invertebrate drift leaving the experimental reach came predominantly from the downstream 10 m section, and larger numbers were caught in drift samples when fishing proceeded in a downstream direction. This was probably because the electrode passed over invertebrates which had previously entered the drift ‘higher’ upstream and re‐settled on the substrate lower in the reach.

Electric fishing caused a loss to the drift of 9.6% of the total benthos in the experimental area. This was slightly more than the 8% decrease in benthic numbers calculated from bottom samples.