A sampling protocol for the endangered freshwater fish, Oxleyan Pygmy Perch Nannoperca oxleyana Whitley

The conservation of the Oxleyan Pygmy Perch Nannoperca oxleyana would benefit from the adoption of a standardised, non-destructive sampling protocol that effectively and efficiently detects the presence, and quantifies the relative abundance, of extant populations. The objectives of this study were to: (i) quantify the minimum number of traps required to obtain precise relative abundance estimates, (ii) assess the effectiveness and efficiency of various trapping regimes, and (iii) compare the relative detectability and short-term mortality rates of trapping, seine netting and backpack electrofishing. 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 occasions, whereas traps set for 15 minutes did not. Positive correlations were found between set time and both overall (fish/trap) and standardised (fish/trap/minute) catch rates, although only the former relationship was significant. The addition of bait to traps did not significantly affect catch rates. Trapping, seine netting and electrofishing detection rates were 88%, 71% and 83%, respectively. Associated mortality rates were 10%, 55% and 0%, respectively. The deployment of multiple gear types increased the likelihood of detecting N. oxleyana. 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.