The fish community of Hamilton Harbour, Lake Ontario: Status, stressors, and remediation over 25 years

Abstract

Hamilton Harbour is a large (21 km2) protected harbour located at the western end of Lake Ontario that was designated as an Area of Concern in 1985 by the International Joint Commission. As part of the designation, the fish community was deemed “impaired.” One of the long-term goals of the Hamilton Harbour Remedial Action Plan is to rehabilitate the fishery to a state, at least in part, to what it was prior to the degrading effects of industrial and municipal pollution, habitat loss, and invasive species. Since the Area of Concern designation, the nearshore fish community has been monitored regularly via a federal boat electrofishing program (1988–2013) and more recently, by a trap net program (2006–2012). During the study period, the harbour underwent significant physical and biological change which was related to both lake-wide (e.g. Dreissenids) and localized harbour events (e.g. habitat restoration). The fish community was assessed temporally using two indices of ecosystem health, the Great Lakes Index of Biotic Integrity and Proportion of Piscivore Biomass, and species-specific catch trends at unaltered sites or sites modified by habitat restoration. Early on, the fish community was dominated by tolerant species characteristic of degraded, eutrophic environments and piscivore abundance was low. The fish community responded positively to ecosystem actions during the first decade that improved water quality, increased physical habitat and reduced invasive species, but further progress was confounded by the interactions with other factors in the last decade that included new invasive species and a decline in water quality. Fish community assessments in the last decade, using both the indices found that the fish community was still impaired and dominated by non-native and pollution tolerant species. The Index of Biotic Integrity was a suitable indicator of ecosystem health strengthened by a consistent assessment with the Proportion of Piscivore Biomass index. A science based refinement of the existing Index in the future would benefit the ability to assess nearshore fish assemblages in the context of conservation goals.

First signs of macroinvertebrate recovery following enhanced restoration of boreal streams used for timber floating

“…Additional stressors and human impacts, acting either at the local or regional scale, may hinder the recovery of biota after stream restoration, especially in landscapes subjected to multiple human pressures (e.g., Boston et al 2016). However, it is highly unlikely that such factors influenced our results given the very low level of anthropogenic impact in the catchment, apart from channelization for timber floating.…”

“…Often, this entails restoration of the physical complexity of degraded habitats, based on the assumption that this will enhance biodiversity, promote recolonization by more environmentally sensitive species and habitat specialists, and enhance ecosystem functioning (Palmer et al 1997, Pretty et al 2003, Kail et al 2007, Frainer et al 2017. However, the effectiveness of habitat restoration has been limited in several habitat types, including wetlands (Simenstad andThom 1996, Moreno-Mateos et al 2012), lakes (Boston et al 2016), woodlands (Wilkins et al 2003), and seagrass beds (van der Heide et al 2007). However, the effectiveness of habitat restoration has been limited in several habitat types, including wetlands (Simenstad andThom 1996, Moreno-Mateos et al 2012), lakes (Boston et al 2016), woodlands (Wilkins et al 2003), and seagrass beds (van der Heide et al 2007).…”

“…Indeed, higher physical complexity has been related to higher biodiversity in near-natural systems, and losses of biodiversity have been documented for degraded systems with reduced physical complexity (Beisel et al 2000, Passy andBlanchet 2007). However, the effectiveness of habitat restoration has been limited in several habitat types, including wetlands (Simenstad andThom 1996, Moreno-Mateos et al 2012), lakes (Boston et al 2016), woodlands (Wilkins et al 2003), and seagrass beds (van der Heide et al 2007). Similarly, follow-up studies of habitat restorations in streams and rivers have found that although physical complexity is frequently enhanced, this has often failed to generate the desired responses within target organism groups or ecosystem functions (Pretty et al 2003, Lepori et al 2005, Nilsson et al 2017, though examples of more successful outcomes exist (Miller et al 2010, Verdonschot et al 2016, Frainer et al 2017.…”

Hamilton Harbour Remedial Action Plan process: Connecting science to management decisions

“…Finally, this special issue examines the biotic community dynamics of HH, commonly referred to as "fish and wildlife" in this AOC. Presented are articles on the population trends in nesting colonial waterbirds (Zanchetta et al, 2016), comparison of HH fish community with other Lake Ontario sites (Boston et al, 2016) and aquatic vegetation trends from 1992 to 2012 in Hamilton Harbour and Cootes Paradise (Leisti et al, 2016).…”

The Use of Biotelemetry in Management of Areas of Concern in the Laurentian Great Lakes

“…Assessment of the water chemistry associated with fish habitat involves surface and water-column sampling for temperature, dissolved oxygen (DO), sediment, contaminants and metals. Current fish population monitoring schemes to quantify restoration success across multiple sites in the Great Lakes use local or regionally derived indices of biotic integrity, which consider the fish community trophic composition, including invasive species (Brousseau et al, 2011;Hoyle et al, 2012;Boston et al, 2016;Hoyle et al, 2016).…”