Freshwater fish functional and taxonomic diversity above and below Niagara Falls

Karl A Lamothe,D Andrew R Drake,Justin A G Hubbard

doi:10.1007/s10641-020-01044-w

Karl A Lamothe, D Andrew R Drake + Show 1 more

Open Access

https://doi.org/10.1007/s10641-020-01044-w

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Abstract

The Niagara River, which connects two Great Lakes (Erie and Ontario) and forms a border between Canada and the United States, has experienced decades of abiotic and biotic disturbance as well as long-term restoration efforts. Given the iconic riverscape and importance as a binational fisheries resource, a biodiversity assessment of the mainstem Niagara River fish assemblage is overdue. Here, fish assemblage and habitat data from a standardized boat electrofishing program of the Niagara River were combined with species trait data related to substrate associations, diet preferences, reproductive strategies, and body size to quantify biodiversity patterns among river sections (sites above and below Niagara Falls), seasons (spring, summer, fall), and years (2015–2017). Sixty-five species were captured representing a variety of trait combinations. Significant differences in functional dispersion and divergence (i.e., functional diversity) were observed between river sections, seasons, and (or) years. The fish community captured in the lower river in spring 2015 had both the highest average functional dispersion (2.08 ± 0.32 SD) and divergence (0.88 ± 0.04 SD) compared to the other seasonal sampling efforts, but relatively few fishes were captured (n = 686). Although non-native fishes represented a small portion of the catch over the 3 years (8.6% of catch), the seasonal presence (spring and fall) of mostly introduced large-bodied salmonids expanded functional trait space in the lower river during these periods. The importance of rare species on functional diversity metrics suggests further insight on local species detection probabilities is needed to understand if differences in functional diversity reflect ecological patterns or are driven by sampling design.

Highlights

Biodiversity assessments are often used to inform species conservation and habitat management, but have traditionally focused on taxonomic metrics of diversity dependent on evolutionary history
Maintaining species richness increases the likelihood that ecosystem function will be preserved when disturbance occurs, traditional taxonomic metrics do not always correlate with the suite of ecological functions present in a community (Cadotte et al 2011)
55 species were observed in the lower Niagara River compared to 57 in the upper river

Summary

Introduction

Biodiversity assessments are often used to inform species conservation and habitat management, but have traditionally focused on taxonomic metrics of diversity dependent on evolutionary history (e.g., species richness). Maintaining species richness increases the likelihood that ecosystem function will be preserved when disturbance occurs (i.e., insurance hypothesis of biodiversity; Yachi and Loreau 1999), traditional taxonomic metrics do not always correlate with the suite of ecological functions present in a community (Cadotte et al 2011). Functional diversity metrics have been used to understand the mechanisms leading to species extinctions (Cardinale et al 2012), to evaluate the success of management actions and inform environmental protection efforts (Ikin et al 2019), and to estimate the vulnerability of ecosystems to the effects of future disturbance (Mouillot et al 2013a). Combining traditional taxonomic metrics with functional diversity metrics can provide a more robust understanding of local and regional biodiversity patterns (Cadotte 2011)

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