Management Plan for the Bridle Shiner in Canada [Final] 2011: Threats

The COSEWIC status report (Holm et al. in press) states that the Bridle Shiner has a limited distribution in Canada and is susceptible to increased water turbidity from agricultural practices and urban development.

Currently, known and suspected threats to the Bridle Shiner include agricultural pollution, urban and industrial pollution, local modification of natural flow regimes (e.g., channelization, artificial drainage and wetland filling), removal/destruction of riparian vegetation, removal/destruction of aquatic vegetation, large-scale fluctuation of water levels, climate change, exotic species and disease spread and commercial baitfish harvesting.

Table 5 summarizes known and suspected threats to the Bridle Shiner in Canada. In general, threats have been listed in order of perceived impact. The severity of the threats and the overall level of concern may vary depending on the individual populations.

The threat classification parameters are defined as follows:

Extent – the spatial extent of the threat (widespread/localized);
Occurrence – indicates if the threat is present or expected (current/imminent)
Frequency – the frequency with which the threat occurs (seasonal/continuous);
Causal Certainty – the level of certainty that it is a threat to the species (high, medium, low);
Severity – the severity of the threat (high, medium, low); and,
Overall Level of Concern – the composite level of concern regarding the threat to the species (high, medium, low).

Table 5. Threats to Bridle Shiner populations in Canada, listed in order of their overall level of concern, from highest to lowest (some variability may occur in the severity and level of concern at specific locations).

1. Agricultural Pollution: As its congeners of the Notropis genus, the Bridle Shiner is sensitive to environmental changes as habitat degradation and poor water quality conditions that can occur in water bodies located within intensive agricultural areas (Holm et al. in press). Therefore, the species' presence can be a good indicator of environmental conditions, particularly in agricultural environments. Backfilling of marshes, channelization, eutrophication, sediment input, as well as increased turbidity, are believed to be responsible for the decline of the species across its North American range. These negative impacts are commonly associated with agricultural practices related to crop and livestock production, and particularly corn production. In Québec, corn crops have experienced a significant expansion since 1970 throughout the range of the Bridle Shiner. Excess fertilizer (i.e., nitrogen and phosphorus), which is the principal impact of corn farming, results in the eutrophication of water bodies, thereby negatively impacting fishes (FAPAQ 2002, Vachon 2003). With the exception of the St. Lawrence River, the majority of locations where the Bridle Shiner has been observed are seriously impacted by eutrophication (Holm et al. in press, Robitaille 2005). Agricultural practices also include various contaminant inputs to which the Bridle Shiner could be exposed.

Increases in turbidity, due predominantly to agricultural practices, may prevent the Bridle Shiner from locating food and impedes the growth of submerged aquatic plants, on which the species depends (Holm et al. in press). Poor land use practices contribute to turbidity through increased input of fine particulate matter that does not settle out of the water column. Grazing and trampling of riparian vegetation by livestock decreases its capacity to act as a buffer zone and increases bank erosion, sediment re-suspension, and siltation of water bodies (FAPAQ 2002, Vachon 2003).

2. Urban and Industrial Pollution: The development and exploitation of resources, as well as urbanization, are the cause of several sources of pollution throughout the Canadian range of the Bridle Shiner. The presence of urban and industrial pollutants in aquatic environments results in a decline in water quality and can have a negative impact on various stages of the life cycle of fish.

Wastewater from cities, textile mills, pulp and paper mills and mines, contains several chemicals, such as heavy metals (e.g., lead and mercury), chlorinated hydrocarbons (e.g., dichlorodiphenyltrichloroethane [DDT] and polychlorinated biphenyls [PCBs]) and polycyclic aromatic hydrocarbons (e.g., benzopyrene). Some of these chemicals disturb the endocrine system of organisms exposed to these wastewaters and cause malformations as well as reproductive and developmental problems for many fish species that co-habit with the Bridle Shiner (e.g., White Sucker [Catostomus commersonii], Spottail Shiner [Notropis hudsonius] and Copper Redhorse [Moxostoma hubbsi]) (de Lafontaine et al. 2002, Jobling and Tyler 2003, Aravindakshan et al. 2004). In addition, increases in turbidity or water temperature that may negatively impact the Bridle Shiner can be associated with effluent releases.

3. Local Modification of Natural Flow Regimes (e.g., Channelization, Artificial Drainage and Wetland Filling): In Quebec, more than 25 000 km of streams and rivers were straightened between 1944 and 1986 (Roy 2002) to permit or increase agricultural production. This has resulted in the loss of many habitat features (e.g., instream cover, undercut banks), making the streams uniform in nature and creating changes in their hydrological regimes. Rain and snowmelt saturate soils with water and increase flow rates; this is intensified in streams that have been straightened, resulting in higher turbidity, the collapse of riverbanks and shoreline erosion (FAPAQ 2002, Robitaille 2005). This would likely have a negative impact on Bridle Shiner populations. In Ontario, the tributaries of Lake St. Francis, which have been historically inhabited by the Bridle Shiner (i.e., Wood, Finney, Gunn and Fraser creeks), are located within agricultural areas. Stretches of these tributaries are now maintained (i.e., dredged) as agricultural drains; this has negatively impacted the Bridle Shiner (B. Jacobs, Raisin Region Conservation Authority, pers. comm. 2008).

During low flow periods in summer and winter, reduced water infiltration due to runoff and drainage practices as well as increased urbanization and the related increase in impermeable surfaces (i.e., more paved areas), result in lower aquifers and interrupted base flows. In some cases this can cause stream desiccation, which could negatively impact Bridle Shiner populations (FAPAQ 2002, Robitaille 2005).

4. Removal/Destruction of Riparian Vegetation: The removal or destruction of riparian vegetation is believed to be of greater concern for Bridle Shiner populations within Québec and the extreme eastern portion of the species' Ontario distribution, in the Cornwall area. As of 2007, the percent riparian cover in the following watercourses where Bridle Shiner was historically found was: Finney Creek: 16.4%, Fraser Creek: 25.8%, Gunn Creek: 4.5%, Wood Creek: 3.5%, Sutherland Creek: 12% (not a historic location). Since 2007 this percentage has likely decreased as the trend in this region is to remove riparian zones since the land is extremely valuable for agriculture (B. Jacobs, Raisin Region Conservation Authority, pers. comm. 2011).

Any human intervention likely to result in increased turbidity can be harmful to the Bridle Shiner (Holm et al. in press). Riparian zones play a significant role in protecting water quality. They slow down and capture particles that are washed onto the soil surface and retain the soil while protecting the banks from lateral erosion. Deforestation and the removal of riparian zones to increase cultivable areas can result in an increase in runoff, water temperature, as well as sediment and nutrient loading in water bodies (FAPAQ 2002, Vachon 2003). Excessive siltation can suffocate deposited eggs, reduce oxygen availability in the substrate and reduce the abundance of food resources (Holm and Mandrak 1996).

5. Removal/Destruction of Aquatic Vegetation: As with the removal or destruction of riparian vegetation, this threat is believed to be of greater concern for Bridle Shiner populations within Quebec and the extreme eastern portion of the species’ Ontario distribution, around Cornwall. Whether it is for spawning or feeding, sites occupied by the Bridle Shiner are typically characterized by an abundance of submerged vegetation. The physical or chemical removal of aquatic macrophytes (e.g., for drain cleanouts, recreational purposes or aesthetic reasons) would be expected to negatively impact the Bridle Shiner (Holm et al. in press). Additional factors that are likely to destroy or reduce aquatic vegetation density include changes in water levels (e.g., as a result of dams), wave action of passing boats, channelization, agricultural drainage, runoffs, pollutants, and exotic plants such as Eurasian water-milfoil (Holm et al. in press, Robitaille 2005).

6. Large-Scale Fluctuation of Water Levels: Fluctuating water levels in the St. Lawrence River are a result, in part, of anthropogenic factors such as hydroelectric dams, agricultural drains and water-taking activities. The river level is controlled to limit spring flooding, facilitate commercial shipping and generate hydroelectric power. The construction of the St. Lawrence Seaway also brought about considerable changes in flow and has an ongoing effect on water levels. Dredging of the shoals and shipping lanes concentrates the flow in the main channel, reduces current velocity in shallow areas and increases sediment deposition. This leads to habitat dessication and loss of submerged aquatic vegetation.

7. Climate Change: Global climate change is expected to have significant effects on the aquatic communities of the Great Lakes and St. Lawrence basin because of major changes in hydrological cycles and in the type and availability of aquatic ecosystems (Environment Canada 2001, Lemmen and Warren 2004). Climate prediction models are becoming more powerful and accurate and they point towards major global and local climate change by the year 2020 (Bourque and Simonet 2008).

In the Great Lakes and St. Lawrence basin, forecasted drying will be associated with a reduction in annual stream flow and lake levels and by the disappearance of ponds and wetlands (Environment Canada 2001, Bourque and Simonet 2007). Models predict reduced flows in tributaries of the St. Lawrence (Croley 2003, Fagherazzi et al. 2005). Lefaivre (2005) concludes that water levels in the St. Lawrence, around Montreal, will be reduced by 0.2 m to 1.2 m and predicts a reduction in open water surfaces, particularly in the relatively shallow Lake St. Pierre area.

Within the Canadian range of the Bridle Shiner, Bourque and Simonet (2008) expect warmer winters, summer "tropicalization", and an increase in frequency, intensity, and duration of extreme climatic events. This anticipated increase in the frequency and magnitude of extreme weather events such as higher precipitation rates, accelerated runoff and snowmelt, will produce higher leaching of sediment and soil erosion and the increased transport of pollutants and nutrients into waterbodies (Environment Canada 2001). Additionally, warming trends may favour the establishment of potentially harmful exotic species that may currently be limited by cooler water temperatures (Environment Canada 2001, Drew et al. 2002). Water-taking as a result of increased demand could further alter habitats (Environment Canada 2001).

Bourque and Simonet (2008) suggest that climate change presents a greater challenge for species at risk with fragmented habitats and low migratory capacity, already coping with several stress factors.

Doka et al. (2006) achieved an assessment of the projected impacts of climate change on coastal wetland fish assemblages in the lower Great Lakes (Bridle Shiner did not occur in the area of study). They found that Pugnose Shiner was highly vulnerable to climate-induced changes in coastal wetlands and nearshore habitats. Pugnose Shiner was ranked sixth most vulnerable out of 99 species assessed. Given the similarities in the two species with respect to habitat requirements, it is reasonable to believe that Bridle Shiner would be as sensitive as the Pugnose Shiner to the impacts of climate change. Furthermore, the only remaining area where the Bridle Shiner is found in abundance is Lake St. Pierre, where the species is likely to be affected by forecasted lower water levels and a reduction in surface area covered by shallow aquatic vegetation (Robitaille 2005).

8. Exotic Species and Disease Spread: Exotic species may affect the Bridle Shiner through several different pathways, including the restructuring of aquatic food webs and competition for space, habitat and food. There are at least 185 exotic species established in the Great Lakes and 88 in the fluvial St. Lawrence (Y. De Lafontaine, Environment Canada – Centre Saint-Laurent, comm. pers. 2009, NCRAIS 2009), some of which impact native species, including species at risk. Dextrase and Mandrak (2006) indicate that while habitat loss and degradation constitute the principal threat affecting aquatic species at risk, exotic species are the second most prevalent threat, affecting 26 of 41 federally-listed freshwater fishes across Canada.

The Common Carp (Cyprinus carpio), Round Goby (Neogobius melanostomus) and Zebra Mussel are exotic species that have had a dramatic impact on many aquatic species and will continue to alter ecosystems and ecosystem processes. The effects of exotic species such as Common Carp and Round Goby on the Bridle Shiner are unknown. Common Carp could have a negative impact on the species through their habit of uprooting aquatic macrophytes essential to the survival of the Bridle Shiner. This would result in a loss of aquatic vegetation and an increase in turbidity levels. In areas where Round Goby has become abundant, the abundance of native benthic fishes (e.g., darters [Percina spp., Etheostoma spp.]) has declined (e.g., Baker 2005); however, it is unclear how the Round Goby may impact the Bridle Shiner. The Zebra Mussel may actually have a positive impact on the Bridle Shiner as its presence results in increased water clarity which would allow more light to penetrate the water, thereby encouraging aquatic macrophyte growth.

Exotic plant species are also a concern in coastal wetland areas as they can significantly change vegetation communities. For example, the introduction in the 1940s of Eurasian water-milfoil, an invasive exotic species, could have a negative impact on the Bridle Shiner. Unlike native species of milfoil, Eurasian water-milfoil forms a dense canopy over the water surface, effectively eliminating the preferred spawning habitat of the Bridle Shiner. This species is of particular concern to the Bridle Shiner as it has been associated with the decline of Blackchin Shiner, Blacknose Shiner, Pugnose Shiner, three species closely related to the Bridle Shiner, as well as the Common Shiner (Luxilus cornutus) (Lyons 1989, Holm et al. in press). The impact of the Eurasian water-milfoil on Canadian populations is consequently expected to be negative (Holm et al. in press, Auger 2006). The potential impacts of other exotic plant species, such as the water chestnut (Trapa natans) on the Bridle Shiner have not been investigated.

Diseases such as Viral Hemorrhagic Septicemia (VHS) are a concern. There are currently no known cases of VHS affecting the Bridle Shiner, and the impact of VHS on this species has not been studied. However, VHS was confirmed from a fish die-off in Hamilton Harbour (western Lake Ontario) in May 2007 (CFIA 2010) and the virus is known to be present in the Lake Ontario watershed. The Canadian Food Inspection Agency (CFIA) considers that the freshwater portion of the St. Lawrence River, east of the Moses-Saunders Dam and directly linked to Lake Ontario, constitutes a watershed which is at high risk of infection (CFIA 2010). In 2007, CFIA implemented a monitoring program to track the virus in wild fishes in Canada, with contributions by its Aquatic Animal Health Division, Fisheries and Oceans Canada (DFO), the Animal and Plant Health Inspection Service of the U.S. Department of Agriculture, the U.S. Fish and Wildlife Service, and the Great Lakes Fish Health Committee (CFIA 2010).

9. Commercial Baitfish Harvesting: In Quebec, a study assessing the impacts of the commercial baitfish industry on five fishes at risk was conducted in the fall of 2005. Over 60 Bridle Shiner were found among the more than 41 500 fish that were sampled in tanks of commercial baitfish harvesters and retailers. The majority of the Bridle Shiner was harvested by the commercial baitfish harvesters in Lake St. Pierre, confirming that the species is common in this location (Boucher et al. 2006). However, the low fishing pressure in this area and the few specimens collected by bait fishermen during the survey indicate that Bridle Shiner populations are not significantly affected. Furthermore, in a similar summer survey in 2007, no Bridle Shiner were identified in the live-wells of commercial baitfish harvesters or retailers. Results from this study also suggest that the impacts of commercial baitfish harvesting on the Bridle Shiner are very low (Garceau et al. in press). In addition, mitigation measures are included in the baitfish harvesting permit and could be adapted to Bridle Shiner management. These measures include commercial harvesting exclusion periods and zones.

In Ontario, the extent to which the Bridle Shiner is affected by baitfish harvesting remains unknown. Baitfish harvesting is regulated in Ontario and the Bridle Shiner is not a legal baitfish (Cudmore and Mandrak 2005, OMNR 2008). However, it may be subject to incidental catch should the baitfish harvest occur in areas occupied by the species.

Quebec –

Surveys : In 2006, an inventory of fish species at risk was conducted in the Montérégie and Outaouais regions to establish the distribution of Eastern Sand Darter (Ammocrypta pellucida), Channel Darter (Percina copelandi) and Bridle Shiner. Specifically, this inventory targeted the watersheds of the Châteauguay River, in Montérégie (Garceau et al. 2007), and the Ottawa River, in Outaouais (Pariseau et al. 2007). This study was conducted by the Ministère des Ressources naturelles et de la Faune (MRNF), with the collaboration of DFO and the Société Provancher d'histoire naturelle du Canada.

In 2002, an ichthyological inventory of rare fish species (Eastern Sand Darter, Channel Darter and Bridle Shiner) was carried out in the southern part of the Assomption River watershed, in the Lanaudière region. Sampling was specifically conducted in L’Assomption, Ouareau and L’Achigan rivers. This project was carried out by CARA, in collaboration with the MRNF and the Des Seigneuries ZIP (Zone d’intervention prioritaire/Area of Prime Concern) Committee (CARA 2002).

The FMN has been conducting systematic sampling of the fish communities in six areas of the St. Lawrence River upstream from Quebec City since 1995: Lake St. Francis, Lake St. Louis, the Montréal-Sorel reach (beginning in 2001), Lake St. Pierre and its archipelago, the Bécancour-Batiscan reach and the Grondines–St. Nicolas reach (La Violette et al. 2003). The locations were first sampled in 1995-1997. A second round of sampling was conducted in 2001-2006, and a third round was begun in 2007.

Baitfish Studies: In 2005, a study was conducted in collaboration with baitfish harvesters to assess the impact of the fall commercial baitfish industry on five (SARA)-listed fish species: Copper Redhorse, Grass Pickerel (Esox americanus vermiculatus), Bridle Shiner, Eastern Sand Darter and Channel Darter. A report was submitted to DFO by the Quebec MRNF with the collaboration of the Société Provancher d'histoire naturelle du Canada (Boucher et al. 2006). In the summer of 2007, another survey continued the project launched in 2005 (Garceau et al. in press). This study was carried out by the Quebec MRNF in collaboration with the Comité de concertation et de valorisation du bassin de la rivière Richelieu (COVABAR) and with the help of DFO (financial support).

Restoration work: In Quebec, restoration work in agricultural watercourses is planned or has been successfully undertaken by local non-profit organizations. Funds from the federal government’s Habitat Stewardship Program for Species at Risk are used to finance these actions.

Ontario –

Baitfish Study: A graduate student from the University of Toronto is conducting a study (initiated in 2007) to examine the impacts of baitfish harvesting on species at risk and the distribution and spread of exotic species. The study is being conducted in cooperation with DFO.

Recent Surveys: Table 6 summarizes recent (since 2000) fish surveys conducted by various organizations throughout the Ontario range of the Bridle Shiner. These surveys did not specifically target the Bridle Shiner, with the exception of the Rideau Canal survey, which targeted four species at risk, including the Bridle Shiner. Raisin Region Conservation Authority conducted fish surveys, specifically targeting Bridle Shiner in 2008, 2009, and 2010 at a number of locations where Bridle Shiner was historically found. DFO also conducted Species at Risk surveys for Bridle Shiner throughout the Rideau Canal System, and Bay of Quinte area in 2009 and 2010.

Table 6: Summary of recent fish surveys (since 2000) throughout the Ontario range of the Bridle Shiner.

a – electro-fishing from a boat; b – seine net; c – fyke net; d – minnow trap; e – hoop net; f – trap net; g –backpack electro-fishing.

Additional knowledge of the distribution, abundance and population trends of Bridle Shiner populations in Canada is required. The species has never been thoroughly studied and available information on the species is limited. It is particularly important to measure population demographics in the portions of the St. Lawrence River where the species is still abundant. Moreover, as the Bridle Shiner can be easily confused with the Blacknose Shiner and other species of blackline shiners, re-examination of preserved specimens in government and museum collections would aid in clarifying historical distribution patterns.

Current knowledge on the species’ biology comes primarily from studies carried out in New England in the 1940s by Harrington (1947, 1948a, b). Additional basic data concerning habitat and life-history requirements and threats facing Canadian Bridle Shiner populations are necessary to prioritize habitat restoration activities for the species. The expanding range of Eurasian water-milfoil, an invasive exotic plant, and its impact on Bridle Shiner populations requires further study. Habitat fragmentation by dams, water-crossings or culverts should also be regarded as a threat to the Bridle Shiner and their impacts should be studied further.

Research on Bridle Shiner genetics could help distinguish between populations or estimate population sizes. Currently, there is no information available on the genetics of the species.

Canada – In addition to (SARA), the Fisheries Act and its supporting regulations have direct or indirect applications to the management of the Bridle Shiner and its habitat. The Fisheries Act has provisions that (a) make fish passage mandatory and require the construction of fish-ways (when deemed appropriate by the Minister) (section 20); (b) prohibit the destruction of fish by means other than fishing, unless authorized (section 32); (c) prohibit the harmful alteration, disruption or destruction of fish habitat, unless authorized (section 35); and, (d) prohibit, subject to regulations, the deposit of deleterious substances into waters frequented by fish (section 36). The provisions of the Fisheries Act and supporting regulations are mostly administered by DFO. Environment Canada administers section 36 of this Actwhich pertains to the release of deleterious substances into watercourses. The Canadian Environmental Assessment Act (CEAA) requires the assessment of the environmental effects of a proposed project. Environmental effects are, among other things, “any change that the project may cause in the environment, including any change it may cause to a listed wildlife species, its critical habitat or the residences of individuals of that species, as those terms are defined in subsection 2(1) of the Species at Risk Act.” In addition, section 79 of (SARA) requires that, during the CEAA review of a project, all effects of the project on a listed species must be identified. If the project is carried out, measures must be taken that are consistent with applicable recovery strategies or action plans to avoid or lessen those effects (mitigation measures) and to monitor those effects.. Finally, Bridle Shiner habitat located within the St. Lawrence Islands National Park is afforded protection through the Canada National Parks Act and related regulations, which are administered by the Parks Canada Agency. In the Rideau Canal, habitat is protected through enforcement of the Historic Canal Regulation under the Department of Transport Act.

Quebec – Bridle Shiner habitat is protected by two pieces of Quebec’s legislation. TheWildlife Habitats Chapter IV.1 of An Act respecting the conservation and development of wildlifeprotects fish habitat on public lands. All activities that are likely to modify a biological, physical or chemical component of fish habitat are prohibited, aside from the exceptions mentioned in the regulations.

Additionally, the Environment Quality Act (EQA) protects fish habitat by prohibiting the release or emission into the environment of any contaminant likely to be prejudicial to wildlife, beyond the quantity or concentration established by the regulations, whether on private or public lands. The EQA also regulates the development and implementation of the Politique de protection des rives, du littoral et des plaines inondables (Protection policy for lakeshores, riverbanks, littoral zones and floodplains) that aims to protect lakes and streams. This policy establishes minimum standards that must, under An Act respecting land use planning and development, be adapted in development plans of regional municipalities. Additionnaly, under the terms of the Agricultural Operations Regulationof the EQA, with the exception of fords, it is prohibited as of April 1st, 2005, to allow livestock free access to water bodies and shorelines.

Ontario – In Ontario, subsection 3(5) of the Planning Act requires that decisions taken by various bodies “be consistent with” provincial policy statement issued under subsection 3(1) of that Act. Paragraph 2.1.3(a) of the Provincial Policy Statement, 2005prohibits development and site alteration in the “significant habitat of endangered species and threatened species”. This will indirectly benefit species of special concern that co-habit with endangered or threatened species. Subsection 2.1.5 of the Provincial Policy Statement, 2005 prohibits development and site alteration in fish habitat except in accordance with provincial and federal requirements which provides some protection to Bridle Shiner habitat. Stream-side development in Ontario is managed through floodplain regulations enforced by local conservation authorities. A majority of the land adjacent to the rivers inhabited by the Bridle Shiner is privately owned; however, the river-bottom is generally owned by the Crown. Subject to permission being granted by the Raisin Region Conservation Authority, aquatic habitats in the Ontario tributaries of Lake St. Francis below Highway 2, which contain Bridle Shiner populations, are protected against wetland fill-in by the Raisin Region Conservation Authority: Regulation of Development, Interference with Wetlands and Alterations to Shorelines and Watercourses (O.Reg. 175/06), which is administered by the Raisin Region Conservation Authority (Holm et al. in press). Bridle Shiner habitat may also be indirectly protected under the Environmental Assessment Act, Environmental Protection Act and the Water Resources Act.