Assessing the applicability of diver-based surveys for monitoring fish populations in lentic lakes

Abstract

Giving the increasing degradation of aquatic ecosystem, it is important to prioritise harmless methods when selecting appropriate research gear. This study confirmed that Underwater Visual Census (UVC) using SCUBA divers and parallel, depth-stratified transects can produce results comparable to standardized gillnet sampling in terms of fish species proportions in lentic freshwater ecosystems with sufficient water transparency. The proportions of young-of-the-year (YOY) fish were similar between the two methods. In older fish, the species proportions showed minor, non-significant variations between methods. Despite some variability in performance during UVC surveys, this variation is not necessarily indicative of an error but may reflect natural fluctuations in fish distribution. Notably, UVC detected a significantly higher number of fish individuals compared to gillnets. Our findings suggest that UVC is a viable, non-invasive alternative to gillnets for surveying nearshore fish populations, providing comparable data quality with negligible impact on the fish community.