Monitoring a New Zealand freshwater fish community using passive integrated transponder (PIT) technology; lessons learned and recommendations for future use

One hundred and thirty individual fish were collected and passive integrated transponder (PIT) tagged in a 100-m reach of a small North Island, New Zealand stream. The positions of the fish were monitored with a hand-held portable PIT antenna over 41 occasions during day and night in 2008/2009. Redfin bully (Gobiomorphus huttoni), shortjaw kokopu (Galaxias postvectis) and koaro (Galaxias brevipinnis) were the most represented and commonly detected species (75%, 73% and 83% detection rates, respectively). Nine longfin eels (Anguilla dieffenbachii) were tagged but only two were later detected. Redfin bullies with lower condition factors than conspecifics were less likely to be detected following tag implantation. Shortjaw kokopu were less likely to be detected but more retained tags than redfins and koaro. No difference in tag detection rates was found over a range of flow levels, nor between surveying during day and night, although a small decline in detection rates occurred as water temperature decreased and with time since sampling. The PIT technique proved to have significant potential for monitoring New Zealand native stream fish communities and has many advantages over previously used techniques, particularly in relation to the collection of fine-scale spatial data on multiple species.