Adapting a multi-species tool for single-species impact assessments: Managing fishes at risk in Canada

To assess the impacts of human activity on fishes and fish habitat, impact assessment tools use single- and multi-species approaches depending on the ecological and socio-economic objectives. In Canadian aquatic ecosystems, single- and multi-species impact assessments are guided by the Species at Risk Act and Fisheries Act, respectively. Yet, for species protected under the Species at Risk Act, the sparse data often require alternative approaches to risk assessment. The goal of this study was to evaluate whether a database-derived multi-species tool - the Habitat Ecosystem Assessment Tool (HEAT) - can be used for single-species impact assessments. Using an empirical example of proposed drain maintenance in a tributary of Lake St. Clair, the net loss of suitable habitat was evaluated across six conservation targets, ranging from single species, such as the pugnose shiner (Notropis anogenus) and the yellow perch (Perca flavescens), to the entire fish assemblage. Model outcomes were compared across various habitat suitability indices, spatial resolutions, and environmental habitat layers. The net loss of suitable habitat varied widely across conservation targets and was greatest for the rare specialist species (pugnose shiner). Single-species conservation targets were more sensitive to variation in spatial resolution and uncertainty in model input parameters. The results of this study emphasize that single- and multi-species conservation targets should not be considered equal, especially when species differ in abundance and niche breadth. This study demonstrates the flexibility of HEAT for evaluating potential impacts of human disturbance on fishes and their habitat. Future development of this tool should expand beyond physical habitat, to include other factors relevant to species distribution and survival (e.g. biotic interactions).