Dogs can detect carp (Cyprinus rubrofuscus) using lake water samples

• Dogs can detect the presence of carp by sniffing water samples. • They performed with high accuracy when lake water was spiked with carp scent. • Good accuracy was also found using lake water with naturalised populations of carp. • Dogs performed with high sensitivity, whereas eDNA performed with high specificity. • eDNA and scent-detection dogs may be complementary technologies. Introduced carp ( Cyprinus spp . ) have caused significant damage to freshwater ecosystems worldwide. Early detection of carp invasions increases the chances of successful eradication; however, current detection methods are resource intensive. This study evaluated dogs’ potential as a surveillance method by assessing their ability to detect carp in naturally sourced water and comparing their performance to environmental DNA detection. Water samples were presented to dogs on an automated apparatus, a system that could be applied operationally. Experiment 1 examined whether dogs could discriminate between carp-free lake water samples and lake water samples spiked with a standardised concentration of carp aquarium water (concentration equivalent to 310 kg carp/ha). Results revealed that dogs could accurately detect the standardised concentration of carp in lake water, with sensitivity and specificity values of >84 % and >77 %, respectively. Experiment 2 examined dogs’ ability to discriminate between carp-containing and carp-free lake samples with varied trophic state and carp biomass. Experiment 3 evaluated generalisation of the dogs’ carp-detection performance to novel lakes with and without naturalised populations of carp. The results suggest that dogs are capable of stimulus generalisation, classifying lakes as carp-present or carp-absent with greater-than-chance accuracy. Comparisons between dogs and eDNA revealed that both methods are susceptible to detection errors: the dogs demonstrated a liberal classification bias, whereas eDNA demonstrated a conservative classification bias; but, if used together, these methods have the potential to complement each other. Collectively, these findings indicate that dogs have potential to be used as a method for detecting aquatic species using water samples.