Boat electrofishing survey of common smelt and common bully in the Ohau Channel in December 2009

Abstract

We conducted a boat electrofishing survey of the Ohau Channel, which flows from Lake Rotorua to Lake Rotoiti, on 7 December 2009. The purpose of this was to repeat surveys that took place on 13 December 2007 and 11 December 2008 concerning the longitudinal pattern in densities of common smelt (Retropinna retropinna) and common bully (Gobiomorphus cotidianus). Due to run timing and possibly low water clarity and high water flows, catch rates were lower than those found in 2007 and 2008 as we only caught 353 fish comprising three native species and two introduced species in 2.72 km of fished distance at a total of 10 sites. Native species caught were common smelt, common bully and longfin eel (Anguilla dieffenbachii) and introduced species were rainbow trout (Oncorhynchus mykiss) and goldfish (Carassius auratus). The total are fished was 10,884 m² (1.088 ha) giving an estimated density of 3.2 fish 100 m⁻².