Restoration of a New Zealand Lagoon: Evaluation of Two Years of Introduced Fish Control Trials

Increased interest from waterway stakeholders and managers in controlling introduced fishes in selected situations, together with limited knowledge regarding effective means of doing so, makes the reporting of control projects in various environments important. This study reports the results of control trials on an introduced fish assemblage (Salmo trutta [brown trout], Perca fluviatilus [Eurasian perch], and Scardinius erythropthalmus [common rudd]) in a small lagoon in the lower North Island. The trials indicated that repeated netting was an effective means of suppressing introduced fish biomass and could potentially result in eradication if the lagoon was closed off to immigration from the adjacent lake. Increases in native fish density and diversity during the control trials indicated that the reduction in introduced fish biomass could have alleviated predation pressure on these species. In addition perch, and to a lesser degree rudd, completed regular spawning migrations into the lagoon from the lake during spring, providing opportunities for strategic control in the future.