Comparison of fish community metrics between natural and modified open coast shorelines in Lake Ontario

Various shoreline hardening structures are used in open coast environments to reduce erosion caused by wind and wave action and protect infrastructure. As modifications to natural shorelines are increasingly applied, it is important to identify hardening techniques that have minimal negative effects on local fish communities. We compared five fish community metrics (catch, species richness, indices of biotic integrity (IBI) and productivity (HPI), and the presence of non-pelagic fishes) among seven open coast shoreline types sampled during the summer in Lake Ontario, Canada. Using an Integrated Nested Laplace Approximation approach to account for spatial autocorrelation, best fit generalized linear models were identified for each fish community metric based on shoreline types, environmental factors, and proximity features. Artificial groynes (armourstone barriers protruding into the lake) and mixed shorelines (multiple shoreline types) tended to have similar fish community metrics to natural shorelines (sand, mixed, and gravel beaches) and higher metric values than revetments (sloped armourstone shorelines). Catch declined with increasing water temperature at the time of sampling. Sampling sites in close proximity to areas that could provide shelter (e.g., harbours) had higher species richness, IBI scores, and were more likely to contain non-pelagic fishes. This suggests that while some artificial shoreline types have similar fish community metrics to more natural open coast areas and may thus be preferable, local environmental conditions and the proximity of features that can provide shelter from wind and wave action are critical considerations when planning and evaluating shoreline hardening in large waterbodies like the Laurentian Great Lakes.