Advancing Restoration Ecology for Freshwater Fish Habitat of the Laurentian Great Lakes

Following decades of anthropogenic activity in Lake Ontario (LO), Canada, ecological restoration on coastal wetlands has been aimed at preserving biodiversity. However, as resources are typically limited for conservation, it is essential to ensure that such efforts achieve associated goals. Knowledge co-production, a collaborative process where research is conducted in a respectful manner, has been identified as an approach to maximize efficacy for ecological restoration. Aquatic Habitat Toronto (AHT) is a unique consensus-based partnership with diverse member agencies that engage in knowledge co-production and ecological restoration Toronto Harbour (TH). One ecological concern identified by AHT are the negative impacts associated with common carp, Cyprinus carpio, which are a non-native species that established within LO and have negatively impacted freshwater ecosystems by reducing native fish diversity. With acoustic telemetry, I identified potential spawning sites throughout LO, which could be targeted for management actions such as exclusion barriers. I then completed a review examining the implementation of selective fragmentation with exclusion barriers based on biological traits including phenology, sensory capability, morphology, and behaviour. Exclusion barriers have been found to effectively decrease access to common carp spawning sites, but can also hinder movements of native species. To mitigate this issue, I explored differences in phenologies of two native species (largemouth bass Micropterus nigricans, and northern pike Esox lucius) and common carp with predictive modelling of spawning movements to operate barriers seasonally, where native fishes are permitted passage through barriers while common carp movements are inhibited. In addition to common carp exclusion barriers, other restoration techniques have been used throughout TH. To evaluate the efficacy of such restoration efforts, I used discrete and continuous sampling methods. I found that ecological restoration achieved the goals of providing habitat to largemouth bass and decreasing access to common carp with exclusion barriers; however, these barriers likely also had a negative impact on large-bodied northern pike in that their movements into wetlands were hindered. Results from this thesis add to the growing literature base of restoration ecology, providing evidence for environmental managers to mitigate adverse impacts associated with habitat alteration and non-native species for the benefit freshwater biodiversity.

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