Fish as Indicators of Ecological Sustainability: Historical Sequences in Toronto Area Streams

Abstract

A weighted species association tolerance index with respect to water quality (WSATI-WQ) was crafted based on the literature on the sensitivity of different species to certain types of changes in their habitats. This index was used to compare changes through time in ecological conditions at locales in 12 subwatersheds in Toronto streams. As expected, WSATI-WQ scores were generally largest at relatively undisturbed sites and became progressively smaller with increasing deviation from an undisturbed state. Benefits from improved management of sewage have offset some of the degradation associated with earlier urbanization. It appears that modern urban stresses are less harmful to aquatic systems than were urban stresses of the past since some tolerant fish species presently live in urban streams where fish were absent 40 years ago.

Evaluation of single‐pass backpack electric fishing for stream fish community monitoring

“…2007). Two fish‐based approaches have been developed to assess the biological condition of Ontario streams: an Index of Biotic Integrity (IBI) (Steedman 1988), and two indices (SATI‐WQ and WSATI‐WQ) based on individual species tolerances of poor water quality and habitat degradation (Wichert 1994). For the calculation of IBI scores, single‐pass surveys provided representative information on fish abundance, the relative abundance of Rhinichthys spp .…”

“…Cao, Larsen & Hughes 2001). In Ontario, single‐pass backpack electric fishing surveys have been used to describe salmonid‐habitat associations (Stoneman & Jones 2000), and the effects of urbanization (Steedman 1988; Wichert 1994; Stanfield & Kilgour 2006) and impoundments on fish assemblages (Reid 2004). Single‐pass surveys are also widely applied to monitor watershed health and species of conservation concern [e.g.…”

Associations of event‐scale flow hydrology with fish richness in urbanizing Canadian watersheds of Lake Ontario

“…These changes would have increased the acceleration signal without a coincident change in urban cover. Also, improvements to sanitary sewage treatment were made since the 1940s, with improved fish richness in previously impaired streams (Wichert, ). Year served as a surrogate for temporal changes through the 42‐year study period and the bias in the database is evident in the statistically significant positive coefficient for Year in the four‐variable model analyses.…”

“…Sampling sites were selected upstream and downstream of known pollution sources, introducing additional variation into the dataset. As wastewater treatment plant effluent releases ceased, fish community richness improved, potentially masking biodiversity trends associated with urbanization (Wichert, ). The ODPD studies were conducted with seine nets (e.g., ODPD, ), whereas more recent surveys primarily use electrofishing equipment (e.g., TRCA, ). Seine nets are not as efficient as electrofishing techniques because they cannot be effectively deployed in areas with branches, rocky or very soft substrate, or in high velocity currents (Syracuse Research Corporation, ).…”

“…These changes would have increased the acceleration signal without a coincident change in urban cover. Also, improvements to sanitary sewage treatment were made since the 1940s, with improved fish richness in previously impaired streams (Wichert, 1994). The analysis did not have sufficient power to fully explore potential interactions of independent variables with respect to associations with fish richness.…”