Optimal methods for sampling Tench (Tinca tinca) in its introduced range

Monitoring the occurrence and abundance of aquatic invasive species is a significant challenge for managing freshwater ecosystems, given limited resources.Efficient sampling strategies are essential for early detection and accurate population assessment.Here, we sought to identify the most effective methods and site-selection strategies for sampling an introduced riverine population of Tench (Tinca tinca), a globally invasive fish.A comparative analysis of four fishing methods and deployment conditions revealed fyke nets and gill nets as the most effective gears for capturing numbers of Tench, particularly in areas with a speciose fish assemblage.Gill nets and electrofishing were the most effective for Tench detection.To reduce gear-related mortality of non-target fishes during capture efforts, fyke nets should be prioritized in areas with at-risk species or where high levels of bycatch are expected.Although Tench is considered to be most active at night, time of day had no effect on gear capture effectiveness.The presence of vegetation was slightly correlated with the presence of Tench, while substrate type was not, suggesting habitat preferences in Tench may be more flexible than previously thought.Positive associations between Tench and native fishes across heterogeneous sites corroborate a preference by Tench for low-flow, vegetated areas.These associations have the potential to inform site selection for sampling at the invasion front.Our study revealed gaps in knowledge of the ecological relationships between Tench and environmental variables associated with its capture.Nonetheless, our results point to methods for maximizing Tench detection and capture efficiency and for targeting habitats or sites where the species is likely to occur.This information is necessary for informing mitigation plans in established areas and supporting early detection and removal of Tench along the invasion front, with the ultimate goals of slowing its secondary spread.