Carmine shiner (Notropis percobromus) COSEWIC assessment and status report: chapter 10
Limiting Factors and Threats
Too little is known of the carmine shiner’s physiology or ability to adapt to different conditions to identify factors that might limit its survival. The species appears to occupy a relatively narrow ecological niche, which suggests limited adaptive ability. If the carmine shiner’s responses are similar to those of the closely related rosyface shiner, it may show long-term avoidance of pollutants (Cherry et al. 1977) and avoid water temperatures that exceed 27.2 °C (Stauffer et al. 1975). Some other factors that may be important include: the availability of key prey species, predation by other species, competition with other minnows for preferred habitat, diseases and parasites, and hybridization with other shiner species.
Manitoba Aquatic Ecosystem biologists, who are familiar with the carmine shiner, indicate that some or all of the limiting factors/threats listed below are occurring throughout the carmine shiner range (Whitemouth River, Bird River and Pinawa Channel, including the Birch River), and have been documented by Schneider-Vieira and MacDonell (1993) and Clarke (1998). Dams, weirs, and natural falls are also impacts found in the range. The actual severity of the impacts is hard to determine as specific studies have not been done, but the extent of occurrence of these impacts (in the carmine shiner range) is considered to be in the high to medium range (M. Erickson, Manitoba Water Stewardship, Winnipeg, Manitoba, pers. comm. 2006).
Carmine shiners spawn in relatively warm, clear water and frequent shallow flowing water with clean rocky substrates. They may be limited to habitats that offer these conditions, and threatened by activities that alter the turbidity or flow. The closely related rosyface shiner has a narrow range of habitat requirements and responds quickly to changes in habitat and water quality (Smith 1979; Trautman 1981; Humphries and Cashner 1994; Houston 1996). The carmine shiner may show a similar response. Flow impoundment, farmland drainage that increases sediment loads, streambed gravel removal, and stream channelization are examples of activities that have been implicated in the decline or disappearance of the rosyface shiner from streams. Increased bank erosion and consequent siltation probably have negative effects on their eggs, fry, and food supply.
The Carmine Shiner Recovery Team (2005) undertook a detailed threats assessment for each waterbody where the species is known to occur. Four primary categories of threat were identified: habitat loss/degradation, overexploitation, species introductions, and pollution.
Habitat Loss/Degradation
Habitat loss and/or degradation associated with flow regulation, shoreline development, landscape changes and climate change is likely in some reaches of the rivers inhabited by carmine shiners, and may pose a threat to the species. At present it is probably the most significant threat to survival of the carmine shiners, but is difficult to assess given the uncertainties in the species’ distribution and life history requirements.
Because carmine shiners frequent shallow riffles with clear water in summer, flow alterations that affect these conditions may pose a threat to their existence. Hydroelectric development has altered flow in the Winnipeg River. Development on the river mainstem began in 1909 at Pointe du bois, and ended in 1955 with the completion of the station at McArthur Falls (Manitoba Hydro). These stations are still in operation and are unlikely to be removed in the foreseeable future. Another station on the Pinawa Channel was completed in 1906. It was retired in 1951 and has been partially razed. These developments impounded reaches of the river creating forebays, flooding vegetation, and eliminating rapids. Whether these changes increased turbidity and decreased riffle habitat sufficiently to cause a decline in the abundance of carmine shiners in the system is unknown. Over time the turbidity will decrease as flooded shorelines naturalize.
Other activities such as land drainage for farming, highways, and peat extraction; the installation of weirs and river crossings; and removal of nearby vegetation for forestry or agriculture may also affect drainage and thereby flow patterns. The effects of many of these activities on shorelines and runoff can be mitigated. Water removal for domestic use, lawn or agricultural irrigation and for watering livestock can also reduce flow, particularly during dry years.
Peat moss mining occurs in reaches of the watershed upstream from the area known to have carmine shiners. The concern is what effect peat moss removal will have on the hydrography and turbidity of the river. How extensive can peat moss removal be before water storage capacity in the peat is sufficiently reduced so that the stream, or some of its tributaries, become at risk for flash-floods as a result of heavy rainfalls? Similarly, how much can the storage capacity be reduced before the stream is at risk from low flows during dry years? How important is winter water discharge from peatlands in maintaining sufficient flows to keep some open water in rapid or riffle sections, and hence, keep enough oxygen in the water for winter survival? The present operations may not constitute a threat to the biota of the Whitemouth River, but, as "the thin edge of the wedge", they do present a potential future threat, for which more information is needed to assess its importance.
In the past (up to the middle 1990s) water has been drawn from the Whitemouth and other southeastern Manitoba rivers during the winter for pressure testing of sections of newly constructed or repaired pipelines which transect them. The threat, in this case may arise from two areas. First is the abrupt, and large in relation to typical winter natural discharge, change in flows in the affected stream. Increased flow in a recipient stream may break up ice cover, scour the stream bottom, and erode banks, all of which would lead to large increases in turbidity that fish could not avoid under winter conditions. Decreased flow in a donor stream could be so great over the span of a week or more, that instream flow could be interrupted, or nearly so, resulting in shallow areas freezing to the bottom and pools in which fish might survive. Finally, since the water used in these tests is not treated or filtered, the recipient stream could be colonized by exotics, if any occur in the source area. There have been proposals that would involve transfer of water from the Great Lakes to the Brokenhead River; the risk of transfer of exotics is a real hazard (K.W. Stewart, pers. comm. 2006).
Development of the shoreline in areas that provide spawning habitat for carmine shiners, or immediately upstream, could adversely affect spawning habitats by causing physical disturbances or changes in water quality. Clearing of riparian forest to the water’s edge for cottage or agricultural development, for example, can destabilize banks and increase erosion. Allowing livestock access to the river’s edge can also disturb habitats and increase silt and nutrient loading, as can ditching and drainage for local highways. Indeed, most of these effects have been documented along the lower Birch River (Schneider-Vieira and MacDonell 1993; Clarke 1998).
Forestry, agriculture, peat extraction, and highway development all have the potential to change landscapes in ways that alter the patterns and quality of runoff entering waters that support carmine shiners. These changes include, in particular, the removal of vegetation, grading of overburden, drainage of wetlands, and the construction of barriers (e.g., roads) and ditches.
The effects of climate change on carmine shiners are unpredictable. These effects may be positive or negative depending on the direction, extent, and timing of any changes in water temperature and hydrology that affect the species’ habitats. Areas like the Birch River, where low flow and low oxygen conditions already occur in summer and winter (Clarke 1998), may be the most vulnerable to any changes.
Overexploitation
Bait fishing operations may harvest some carmine shiners, but currently the degree of threat to this species is not known. Commercial bait fishing operations are regulated and require a licence. To prevent the spread of undesirable aquatic species, Manitoba Water Stewardship must approve waters for live bait harvest. There are commercial bait fishing allocations in most areas where carmine shiners have been found, but the harvest from specific waters is unknown (B. Scaife, pers. comm. 2004). Licensed commercial bait fishermen may harvest fish for dead bait use from any Crown water on their allocation. Licensed anglers may harvest baitfish for their own use from any Crown water, although live baitfish may be harvested only where live bait use is permitted. Anglers may not transport live baitfish away from the waters in which they were caught.
Most of the commercial baitfish harvest in southeastern Manitoba is directed at collecting fish for sale as live bait (B. Scaife, pers. comm. 2004). The Whitemouth and Bird rivers are both approved for live baitfish harvest. However, most live bait harvest is directed at non-shiner species, which are hardier, have a higher survival rate, and frequent different habitat from shiners. While the use of live traps allows for sorting and release, carmine shiners are difficult for fishermen to identify and easily damaged by handling. Bait fishermen with allocations in the Whitemouth and Bird rivers have not indicated any frozen production on their annual production report forms.
Bait harvesting is of greater concern in areas where baitfish can be harvested only for use as dead bait (e.g., Winnipeg River), since shiners are generally the targeted species. The gear used for these harvests (e.g., seines) is more likely to kill or harm the bait fish than that used for live-capture, but these methods are seldom used in the medium to small stream habitats where carmine shiners are found (K.W. Stewart, pers. comm. 2004).
Despite the regulations, carmine shiners may be inadvertently collected along with other species for bait. Even in cases where the collector is able to identify the species, released individuals are not liable to survive. However, the extent of such collecting is not currently known.
Species Introductions
Species introductions could pose a threat to carmine shiner populations through predation, competition and food chain disruption. They might also carry diseases and parasites that are new to carmine shiner populations and could adversely affect them.
Possible sources of introductions are in water released from the hydrostatic testing of pipelines in the Whitemouth watershed, as live-bait used by anglers, and through the introduction of game fish. The import of live bait into Canada is illegal and should be strictly enforced by Canada Customs. Walleye (Sander vitreus) have been stocked in Whitemouth Lake since 1960, and brook trout (Salvelinus fontinalis) were stocked there in 1961-62 (D. Leroux, pers. comm. 2005; see also Manitoba Fisheries' mandate). The Birch River has been stocked with rainbow trout (Oncorhynchus mykiss), brown trout (Salmo trutta), and walleye with poor survival (Clarke 1998). Brown trout have been stocked in the Pinawa Channel. Smallmouth bass and rainbow smelt (Osmerus mordax) have been introduced to the Winnipeg River system. The effects of these piscivores on carmine shiner populations are unknown, although elsewhere smallmouth bass and carmine shiners do coexist. The potential for transfer of species from the Lake of the Woods watershed via overland drainage exists but is limited at present by beaver dams and bogs.
Pollution
Some pollutants that could affect the species include farm fertilizers, herbicides, and pesticides. Nutrient enrichment by runoff from barnyards or intensive livestock operations is an ongoing problem that is being addressed by the Province of Manitoba and the Prairie Farm Rehabilitation Administration. Clarke (1998) found elevated levels of phosphorus (0.2 mg/L TDP) and nitrogen (0.99 mg/L nitrate/nitrite) in the lower Birch River in April 1996, but not at other times of the year. These levels are probably elevated through mobilization of agricultural chemicals by spring runoff. Before leaks were repaired, the Birch River also received chlorinated water leaking from the Winnipeg Aqueduct (Clarke 1998).
Other Threats
Scientific sampling may also pose a threat to the carmine shiner. However, there has been no evidence of reduction in range or abundance of carmine shiners in Manitoba over the past twenty years, during which there has been regular sampling of the Whitemouth River populations.
Natural hybridization may occur between carmine shiners and other shiners in Manitoba. A substantial decline in the proportion of carmine shiners on the spawning grounds might lead to decreases in reproductive success or complete assimilation of the carmine shiner populations. Given the genetic separation now demonstrated between the Notropis rubellus species complex and other cyprinids this is unlikely (K.W. Stewart, pers. comm. 2006).
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