Responses of three PIT-tagged native fish species to floods in a small, upland stream in New Zealand

Floods are an integral part of flowing river systems, yet our understanding of freshwater fish behaviour during floods is limited. In 2008, 67 redfin bullies (Gobiomorphus huttoni), 22 shortjaw kkopu (Galaxias postvectis) and 29 karo (Galaxias brevipinnis) were tagged with passive integrated transponder (PIT) tags and monitored in a 100-m study reach before, during or after three floods. Detection patterns of tagged fish indicated that they may be displaced or may move to areas with large substrates during floods. Two individuals returned to the same locations during multiple floods, suggesting that previous experience may influence refuge selection for some individuals. While small changes in community composition occurred that could be attributed to concurrent habitat changes, overall a remarkable level of persistence of individual fish was observed in the tagged community.