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Hossein Mehdi, Samantha C Lau, Caitlyn Synyshyn, Matthew Salena, Markelle Morphet, Jonathan Hamilton, Melissa N Muzzatti, Erin S McCallum, Jonathan D Midwood, and Sigal Balshine (2021)

A comparison of passive and active gear in fish community assessments in summer versus winter

Fisheries Research, 242(106016).

Fish populations and communities are monitored using a variety of sampling gears, each with their own inherent biases. Gear biases can arise from a number of factors, such as fish species characteristics (e.g., body shape/size, habitat requirements/preference, physiology, behaviour), species habitat requirements, as well as the abiotic characteristics of sites sampled. Such factors and their effects on gear selectivity are also heavily influenced by seasonality. Consequently, understanding the effects of seasonal changes on gear selectivity is of vital importance, especially during the winter—a season seldom studied in freshwater systems. Here, we compared the selectivity, efficiency, and degree of biodiversity in fish communities sampled using three gear types: minnow traps, Windermere traps, and electrofishing during summer and winter in Hamilton Harbour, ON, Canada. Catch per unit effort was similar among gear types in the summer, whereas in the winter, minnow traps captured the most fish. Electrofishing samples were the most species rich and species diverse, but only during the summer. Additionally, sampling efficiency and the number of different species encountered was highest when all gear types were used in combination, followed by electrofishing alone, Windermere traps alone, and minnow traps alone in both seasons. Each gear type differed in its selectivity for certain species, which was further influenced by seasonality. This resulted in the fish communities caught within each gear type being dissimilar from one another. Our study highlights the importance of understanding gear type selectivity, particularly under different climatic conditions, and outlines the importance of incorporating multiple gear types in ecological assessments of fish populations and communities.