Summary

The Oxleyan pygmy perch Nannoperca oxleyana is a small, freshwater fish found along a narrow belt of lowland, coastal habitat in mid-eastern Australia. The species is listed as endangered and a recovery plan has been prepared by NSW Department of Primary Industries to guide conservation and management programs. The conservation of the Oxleyan pygmy perch would be aided by the adoption of a standardised, non-destructive sampling protocol that effectively and efficiently detects the presence of the fish, and quantifies the relative size of remaining populations. Techniques typically used to sample Oxleyan pygmy perch include trapping, seine netting and backpack electrofishing.

The objectives of this study were to: (i) compare the relative detection and short-term mortality rates of trapping, seine netting and backpack electrofishing, (ii) quantify the minimum number of traps required to obtain precise relative abundance estimates, and (iii) assess the effectiveness and efficiency of various trapping regimes to catch the species. Previous survey data were utilised and augmented with field experiments. Ten traps provided relatively precise estimates of relative abundance. Unbaited and baited traps set for 30 and 60 minutes detected the species on all sampling occasions, whereas traps soaked for 15 minutes did not. The size of the catch increased the longer the traps were set, while the addition of bait to a trap did not affect the numbers of fish caught. Trapping detected Oxleyan pygmy perch on 88% of occasions in which the technique was used. Likewise, detection rates for seine netting and electrofishing were 71% and 83%, respectively. The use of multiple sampling techniques increased the likelihood of detecting the species. Seine netting was associated with a high mortality rate, with 55% of Oxleyan pygmy perch caught with this technique dying. In contrast, only 10% of fish caught in traps died and all fish sampling by backpack electrofishing survived.

A sampling protocol is recommended that includes saturating sites with unbaited traps set for at least 30 minutes and sampling with a backpack electrofisher. Seine netting should be reserved for situations where an electrofisher is unavailable or non-deployable.