Passive sampling approaches and seining revealed limited changes in the fish community of Point Pelee National Park over two decades

Abstract

Point Pelee National Park (PPNP) is a biodiversity hotspot in Canada. Freshwater fish sampling has been conducted sporadically in the open-water wetland ponds over the last two decades to support different objectives. We used multi-gear sampling data from 2002, 2003, 2019, and 2021 and multivariate methods to evaluate differences in fish community composition in PPNP over time. Three data formats were considered: raw counts, catch-per-unit effort (CPUE), and multi-gear mean standardized (MGMS) CPUE, with strong correlations observed in these measures among years. A total of 35,486 fishes encompassing 40 species were captured, with Bluegill (Lepomis macrochirus) and Warmouth (Lepomis gulosus) among the most frequently captured species. Differences in composition within and among ponds were observed. For example, mean Bluegill MGMS CPUE was reduced by 0.49 between 2003 and 2019 in East Cranberry Pond. Across ponds, Bluntnose Minnow (Pimephales notatus) had a relatively high MGMS CPUE in 2002 (0.02 ± 0.16 SD) and 2003 (0.01 ± 0.06 SD) but was not captured in 2019 or 2021. Six species were captured in 2002/2003 but not in 2019/2021, and vice versa. The invasive Tubenose Goby (Proterorhinus semilunaris) was detected for the first time in PPNP in 2021. The underlying causes of the compositional differences are at least in part due to differences in effort and gear-specific detection probability, but are also likely due to intermittent connectivity of wetland habitat with Lake Erie. Overall, results confirm the lack of major community shifts through time, provide insight into the spatial and temporal variability of species-specific CPUE using passive gears, and inform the design of future monitoring programs.