Invasive species now dominate many aquatic landscapes in most parts of the world, displacing native plants and animals by disrupting and altering ecosystems. The brown bullhead catfish (Ameiurus nebulosus) has been significantly correlated with regime shifts from macrophyte‐dominated clear water states to de‐vegetated turbid states, population declines of endemic species, and the disruption of food webs in New Zealand lakes. Conventional detection methods (e.g., visual surveys, fyke netting, electrofishing, and eDNA) for catfish are limited by their cost, invasiveness, time- consumption, and potential to be prone to error. Given that scent detection dogs are a well-established tool across a variety of fields, it was hypothesised that domestic dogs (Canis familiaris) may be able to detect the presence of catfish from water samples that have contained these fish. This could provide a new potential biosecurity monitoring tool. In this study, five pet dogs were trained to operate an automated apparatus that presented water samples for evaluation. Water samples were presented to dogs from aquaria that had previously contained, catfish, goldfish (Carassius auratus), or no fish. Experiment 1 evaluated if dogs could discriminate between samples that had contained catfish or no fish. In Experiment 2, it was evaluated if dogs can discriminate between fish species (i.e., catfish and goldfish), and at what fish biomass concentrations they can do so. Experiment 3 evaluated if dogs could indicate the presence of catfish when samples were presented at two different biomass concentrations in the same session. It was found that dogs were able to correctly identify water that had contained catfish and largely reject water samples that had contained either no fish or goldfish at above 80% accuracy at biomasses equivalent to environmental biomasses of 4.6 x 1,000 kg/ha. Preliminarily investigations of lower detection limit thresholds were investigated in the study. These results suggest further investigation is warranted to confirm the dogs’ ability to detect catfish at biologically relevant concentrations comparable to real-world sample scenarios. However, these findings support the suggestion that dogs may have an important role to play in waterway conservation and management.