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Understanding population-level habitat requirements is important for the effective conservation of imperilled species, especially for those with fragmented distributions. This study examined fine-scale distribution of the threatened pugnose shiner (Notropis anogenus) in the upper St. Lawrence River, Ontario, Canada. Occupancy modelling, multivariate analyses, and co-occurrence modelling were used to identify environmental correlates of pugnose shiner distribution and species associations in an embayment area, Thompson’s Bay. The pugnose shiner was most abundant in outer bay sites that were cooler, less turbid, had a higher pH, and had more submerged aquatic vegetation than the inner bay sites. The probability of pugnose shiner occupancy increased with distance from the inner bay and with the presence of Chara vulgaris, and decreased with increasing conductivity. The pugnose shiner positively co-occurred with seven species, including the blackchin shiner and blacknose shiner, and negatively co-occurred with bluegill. Centrarchid species were dominant across Thompson’s Bay. This has important conservation implications because some native centrarchid predators are increasing in abundance, coincident with climate change, which may threaten the persistence of rare and imperilled cyprinids such as pugnose shiner.

For freshwater fishes, elevated water temperatures associated with climate warming and hypoxia can co-occur and are likely to interact as both affect oxidative metabolism. We quantified the effects of acclimation to elevated temperature and hypoxia on the thermal tolerance of pugnose shiner (Notropis anogenus), a cyprinid fish threatened in its Canadian range. In one experiment, pugnose shiner underwent two-week sequential acclimations to six increasing temperatures. Fish acclimated to warmer waters increased their critical thermal maximum (CTmax), while the agitation temperature (Tag) was 3.4 °C lower than the CTmax. In another experiment, fish were acclimated to three dissolved oxygen treatments (>95%, ∼56%, or ∼40% air saturation) for two weeks and tested under >95% and 40% conditions. CTmax was lower when measured under 40% for normoxia-acclimated fish but not for hypoxia-acclimated fish. Hypoxia-acclimated fish had higher Tag and smaller agitation windows than normoxia-acclimated fish, suggesting that hypoxia acclimation improves aspects of thermal tolerance. We examine the plasticity of thermal tolerance of pugnose shiner, showing that they may be more vulnerable to high temperatures compared with other non-imperiled Notropis species.

One third of the total global land viable for agricultural production has artificial drainage systems. These drainage systems can provide important habitat for fishes and, in some cases, imperiled fish species vulnerable to impact by drainage maintenance activities. A framework to provide quantitative assessments of the effects of maintenance activities on imperiled fish species is needed. In this study, a six-step habitat-based framework was developed to predict suitable habitat for two at-risk species in an agricultural drain: the Endangered Pugnose Shiner ( Notropis anogenus) and the Special Concern Blackstripe Topminnow ( Fundulus notatus) . Using the framework, spatial models were developed to assess the effects of proposed drain maintenance on the overall amount of suitable habitat, habitat patch size, and connectivity of habitat patches. Maintenance had a significant impact on habitat connectivity, but did not significantly reduce the habitat size of isolated patches. The amount of suitable habitat available after maintenance fell below the minimum area for population viability (MAPV) for the Pugnose Shiner, but not the Blackstripe Topminnow. Future impact assessments of drain maintenance should incorporate population viability analysis, coupled with habitat patch analysis (patch size and connectivity), to quantitatively test consequences of proposed alteration to the viability of spatially structured populations.

Increased sedimentary turbidity associated with human activities is often cited as a key stressor contributing to the decline of fishes globally. The mechanisms underlying negative effects of turbidity on fish populations have been well documented, including effects on behavior (e.g. visual impairment) and/or respiratory function (e.g. clogging of the gills); however, the long-term physiological consequences are less well understood. The decline or disappearance of several blackline shiners Notropis spp. in the Laurentian Great Lakes has been associated with increased turbidity. Here, we used non-lethal physiological methods to assess the responses of 3 blackline shiners under varying degrees of threat in Canada (Species at Risk Act; pugnose shiner N. anogenus: endangered; bridle shiner N. bifrenatus: special concern; blacknose shiner N. heterolepis: common) to increased turbidity. Fish were exposed for 3 to 6 mo to continuous low levels of turbidity (~7 nephelometric turbidity units, NTU). To test for effects on respiratory function, we measured both resting metabolic rate (RMR) and critical oxygen tension (the oxygen partial pressure at which the RMR of fish declines). No change in RMR was detected across species or in clear versus turbid treatments. However, critical oxygen tensions were negatively affected by long-term exposure to low levels of sedimentary turbidity in the 2 imperiled species, viz. pugnose and bridle shiner, but not in the more common blacknose shiner. Variation in effects of turbidity on respiratory performance suggests differential sensitivity to turbidity, which may contribute to the current conservation status of the 3 species.

The pugnose shiner, Notropis anogenus , is a small minnow that occurs in the Great Lakes basin and Upper Mississippi River basin. It was listed as ‘Endangered’ under the Canadian Species at Risk Act (SARA) and by the State of New York, largely due to its rarity, fragmented distribution, and degraded habitat. Our objective was to use species distribution modeling to better understand the spatial extent of suitable habitat for the pugnose shiner in the upper St. Lawrence River and to guide protection of habitat for this endangered species. We performed our analyses with MaxEnt, a species distribution modeling method based on maximum entropy. The pugnose shiner is associated with shallow areas of lakes or slow-moving rivers with abundant submerged aquatic vegetation. Therefore, we created a model based on depth, water velocity, and aquatic vegetation. For water depth and velocity, we used results of a two-dimensional hydrodynamic model from the Upper St. Lawrence River generated and calibrated by Environment Canada. Aquatic vegetation was estimated from a simple algorithm based on water depth and velocity. To minimize the effect of sampling bias in the analysis (i.e., sampling occurred predominantly in shallow waters), we also used restricted depth ranges in model generation. Our model produced highly significant results when depth was not restricted, and significant results for analyses with restricted depth ranges. Our results suggest an abundance of potentially suitable habitat for the pugnose shiner in the Upper St. Lawrence River, which exceeded the minimum area for viable population estimates for this species.

The use of non-lethal experiments to elucidate behavioural and physiological thresholds to environmental stressors can provide valuable data for identifying threats to, and critical habitat of, imperilled species. Increased turbidity contributes to population declines and loss of fish diversity globally, but the complex direct and indirect effects of this stressor on imperilled species are not well understood. Response to turbidity was examined in a group of closely related North American fishes (Notropis spp.), including four imperilled shiners: pugnose shiner (N. anogenus), bridle shiner (N. bifrenatus), blacknose shiner (N. heterolepis), blackchin shiner (N. heterodon), and the more common mimic shiner (N. volucellus). Two experiments quantified (i) the behavioural response of each species to progressively increasing turbidity, and (ii) critical swimming speed of fishes acclimated in turbid- and clear-water treatments to provide insights into effects of low turbidity on aerobic performance. Very low levels of turbidity (

The Pugnose Shiner is a small minnow with a fragmented distribution across the Great Lakes and Upper Mississippi River in North America. The species is listed federally as endangered in Canada, and in the United States its status varies by state, from Special Concern to Endangered (as well as Extirpated). We conducted a thorough genetic assessment of the Pugnose Shiner using both microsatellite loci and mitochondrial DNA collected for samples across the species range. Our results indicate high levels of population differentiation suggesting restricted dispersal, in some cases at very small geographical scales. We also found strong evidence of small effective population sizes and one case of a genetic bottleneck. Although significant range-wide genetic variation was observed in both microsatellite loci and mitochondrial DNA, the species is best characterized as a single evolutionarily significant unit for conservation purposes.

Pugnose shiner (Notropis anogenus) and blackchin shiner (N. heterodon) are classified as endangered and of special concern, respectively, in New York and were thought to be rare in the Thousand Islands area of the St. Lawrence River. Both species were caught in 1993–1995, at historic Thousand Islands collections sites (in 1931 and 1983) and at new locations. Blackchin shiner occurred in 11 of 50 samples and pugnose shiner in 4 of 50 in 1993–94. In 1995, sampling extended 93 km downstream and neither species were collected there. When blackchin shiner were collected, there was a high probability of also catching pugnose shiner (regression coefficient of P=0.006). Other species commonly associated with these included tessellated darter, bluntnose minnow, banded killifish and bluegill. The population status for pugnose and blackchin shiners seems unchanged in the Thousand Islands area since the 1930's. The downstream area to Massena, Middle Corridor and Lake St. Lawrence, had no pugnose shiners and ...

Since 1900, major changes have occurred in the assemblage of small littoral-zone fishes (maximum total length