Recovery Strategy for Gravel Chub
1.1 Species Assessment Information from COSEWIC
Common Name: Gravel Chub
Scientific Name: Erimystax x-punctatus
COSEWIC Status: Extirpated COSEWIC
Reason for designation: Last reported in Canada in 1958, gravel chub was possibly lost due to siltation of the rivers where it had occurred.
Canadian Occurrence: No longer found in Canada.
COSEWIC Status History: Last recorded in the Thames River drainage, Ontario in 1958. Designated Endangered in April 1985 and uplisted to Extirpated in April 1987. Status re-examined and confirmed in May 2000. Last assessment based on an existing status report.
The following description is from Trautman (1981) and Becker (1985). The gravel chub (Figure 1) is a slender, round-bodied minnow with an average length of 76 mm TL and a maximum length of approximately 100 mm TL. It is olive-green dorsally with silvery sides and a white belly. The scale margins on the back and sides of the gravel chub are randomly outlined in black resulting in X-, Y- or W-shaped patterns. These markings are sometimes absent in large adults, and were usually faintly evident in Ontario specimens (Scott and Crossman 1998). A small black spot is usually predominant on the base of the caudal fin (except in Ontario specimens) (Scott and Crossman 1998). Fins are transparent or silvery with no spotting. The snout is rounded and long, overhanging the mouth, which has small but conspicuous barbels in each corner.
Figure 1. Gravel chub (Erimystax x-punctatus)
Hubbs and Crowe (1956) assigned Canadian populations of gravel chub to the subspecies E. x. trautmani, which is morphologically distinct from the subspecies E. x. x-punctatus. E. x. trautmani has a relatively pointed, down-curved and long muzzle compared to E. x. x-punctatus which has a blunter, straight, short muzzle. The snout in adult E. x. trautmani is typically longer than the postorbital, while the snout of E. x. x-punctatus is approximately as long as the postorbital. E. x. trautmani has a slender caudal peduncle (least depth averaging about 0.3 less than snout length), whereas the caudal peduncle of E. x. x-punctatus is usually deeper (least depth averaging about 0.1 less than snout length).
Genetic validation for the subspecies designation was confirmed by Simons (2004) based on the cytochrome b gene.
1.3 Populations and Distribution
GlobalRange (Figure 2): In the United States, the gravel chub has a discontinuous distribution from Kansas to New York, and southern Minnesota to Arkansas (NatureServe 2006). It occurs in Arkansas, Illinois, Indiana, Iowa, Kansas, Minnesota, Missouri, New York, Ohio, Oklahoma, Pennsylvania, West Virginia and Wisconsin. It is presumed extirpated in Kentucky.
The subspecies E. x. trautmani is limited to the Ohio River basin in Illinois, Indiana, Ohio, New York, Pennsylvania and Kentucky. In Canada, E. x. trautmani was present only in the Thames River, Ontario.
Figure 2. Global distribution of gravel chub (information from Page and Burr 1991).
Canadian Range (Figure 3): In Canada, the gravel chub was only known from two locations in the Thames River drainage: at Munsee (Oneida Nation of the Thames) and in a stretch of the river in Mosa and Oxford townships, upstream of land owned by the Delaware of the Thames (Moravian Town) First Nation (or Delaware Nation Council (Moravian of the Thames). These locations are approximately 300 km from the nearest American records in Ohio. This species has not been collected in Canada since 1958 (Parker et al. 1988).
Figure 3. Canadian distribution of gravel chub.
Percent of Global Range in Canada: Less than 5% of the species global range occurred in Canada (TRRT 2005).
Population Size and Status:
Global Population Size and Status: The population size of the gravel chub in the United States is unknown; however, it is believed to be at least 10 000 individuals (NatureServe 2006). This species is considered Apparently Secure (G4) globally, and Nationally Secure (N4) in the United States. The status of the gravel chub in the states where it occurs is: Arkansas (S3?), Illinois (S1S2), Indiana (S4), Iowa (S3), Kansas (S2S3), Kentucky (SX), Minnesota (S3), Missouri (SNR), New York (S1), Ohio (S3), Oklahoma (S2S3), Pennsylvania (S1), West Virginia (S1) and Wisconsin (S1S2) (NatureServe 2006).
Canadian Population Size and Status: In Canada, the gravel chub has been listed as Presumed Extirpated nationally (NX) and provincially (SX) as no specimens have been collected in Ontario since 1958 (NatureServe 2006). The population size of the historic gravel chub in the Thames River is unknown; however, specimens collected in 1923 and housed at the University of Michigan’s Museum of Zoology were of different size classes, suggesting these populations were established (B. Cudmore, DFO, pers. obs.).
Nationally Significant Populations: The Thames River populations of gravel chub were the only representation of this genus in Canada and of this species in the Great Lakes basin.
1.4 Needs of Gravel Chub
1.4.1 Habitat and Biological Needs
Historically Occupied Habitat: The 1923 Thames River gravel chub site was located between the mouth of Hogg Creek and a point on the Thames at Munsee (Holm and Crossman 1986). Habitat at this site was described as clear water, fast currents, substrates comprised of clean sand and gravel and depths up to 1.5 m (Parker et al. 1987). The river width at the capture location in 1923 is unknown; however, in the mid-1980’s it was approximately 20-30 m (Parker et al. 1987). In 1958, nine gravel chub were captured while trawling from Lot 16 in Mosa Township to the eastern limit of the Moravian Indian Reserve (Holm and Crossman 1986). No habitat data are available for this capture location
In the United States, gravel chub have been collected from clear to moderately turbid streams containing abundant riffle areas with silt-free sand, gravel or rock substrates (Trautman 1981, Parker et al. 1987). Moore and Paden (1950) suggest that the specific microhabitat for the gravel chub may be under rocks in riffles, reducing the effects of rapid currents. When disturbed the gravel chub has been observed to hide swiftly under rocks. It avoids areas with aquatic macrophytes, aquatic mosses and larger species of algae (Trautman 1981).
In Ohio, gravel chub were found in medium to large streams, at depths of 0.3-1.2 m during the summer and at 0.6-1.8 m during the winter (Trautman 1981). In Wisconsin, specimens were collected from turbid waters, devoid of aquatic vegetation, over swift gravel riffles 0.3-0.9 m deep. Stream width at capture sites was 9-12 m (Becker 1983). No information is available concerning movement patterns or overwintering habitat requirements of adult gravel chub. Differences in habitat use by male and female gravel chub have not been reported. Habitat requirements of young-of-the-year or juvenile gravel chub are unknown.
Currently Occupied Habitat: Currently there are no known occupied habitats in the Thames River.
Habitat Trends: The habitat at the Thames River gravel chub capture sites has shifted from clear to highly turbid water. Based on Jackson Turbidity Units, the lower Thames River remains highly turbid (69.5). Since the 1970s, phosphorous levels at most sites in the watershed have shown a gradual downward trend but remain above the provincial guidelines (30 ug/L) for the protection of aquatic life. Nitrate levels at all monitoring sites in the Thames River have increased over the past 30 years (Taylor et al. 2004). Chloride levels have also shown a continual increase at sites across the watershed but in most cases remain below the Environment Canada level of toxicity for sensitive aquatic species (Taylor et al. 2004).
Habitat Protection/Ownership: The majority of land adjacent to the Thames River is privately owned and in agricultural, industrial or urban use. Gravel chub habitat is protected under the habitat provisions of the federal Fisheries Act. The gravel chub and/or its habitat is also protected under Ontario’s Lakes and Rivers Improvement Act, Environmental Protection Act, Environmental Assessment Act and Water Resources Act. If gravel chub is reintroduced and critical habitat is then defined, the critical habitat of the gravel chub will be specifically protected under the Species at Risk Act (SARA) (TRRT 2005).
General Biology: Little is known regarding the biology of the gravel chub in Canada and most available information comes from populations in the United States (Parker et al. 1987). In the United States, gravel chub have been reported to spawn during the spring in areas of rapid current over gravel riffles (Becker 1983, Parker et al. 1987). In Kansas, spawning took place in April at a water temperature of 15.5°C (Becker 1983). The length of the spawning period is unknown; however, it is assumed to be limited to a brief period in early spring (Becker 1983). Non-adhesive eggs are scattered over the gravel substrate where they remain until hatching. No parental care is given (Coker et al. 2001). Temperature preferences of adult gravel chub are unknown. Gravel chub probably feed on epibenthic insects (Becker 1983, Scott and Crossman 1998) likely obtained from probing under rocks and crevices with its sensitive snout (Parker et al. 1987).
1.4.2 Ecological Role
As this species has not been found in the Thames River (or Canada) for nearly 50 years, its ecological role in the watershed is unknown (TRRT 2005). The gravel chub feeds on benthic invertebrates and may be preyed upon by piscivorous species such as rock bass (Ambloplites rupestris) and smallmouth bass (Micropterus dolomieu) found in the Thames River (McAllister et al. 1985).
1.4.3 Limiting Factors
Gravel chub have very specific habitat requirements that restrict populations to areas with clean sand or gravel with swift currents.
The narrow habitat requirements of the gravel chub make it vulnerable to habitat degradation and declines in water quality. Increased siltation was associated with the extirpation of the gravel chub in many parts of Ohio (Trautman 1981) and Wisconsin (Becker 1983). In Iowa and Minnesota, gravel chub populations may have been extirpated as a result of pesticides, sewage or siltation (Schmidt 2000). Impoundment of essential riffle areas is also a serious threat to the gravel chub in the United States (Becker 1983, NatureServe 2006). Dams alter upstream and downstream habitat conditions and act as barriers, fragmenting populations and limiting re-colonization. Most dams in the Thames River watershed are either in the upper watershed or tributaries to the lower and middle Thames River. The Springbank Dam, situated in northwest London, is the most downstream barrier along the mainstem of the Thames River. When stop-gates are in place from mid-May to early November, it is a barrier to fish passage and creates a small upstream run-of-the-river type impoundment (55 hectares). With the exception of filling the reservoir in mid-May and draining the reservoir in November, the dam has little effect on downstream flows. Therefore, historical habitats of gravel chub are not expected to be affected by dams in the Thames River.
Siltation and turbidity are believed to be the primary reason for the decline and eventual extirpation of the gravel chub from Ontario. Gravel chub collection sites on the Thames River were described in 1923 by D.E.S. Brown (cited in Parker et al. 1987) as fast flowing with clear water, and substrates of sand and gravel. In 1985, Holm and Crossman (1986) indicated a shift in habitat conditions as clay and silt were present at all sites and the water was very turbid. Nutrient loading as a result of agricultural and urban practices (e.g. fertilizers, manure spreading, sewage treatment) may have also contributed to its extirpation.
1.5.1 Threat Classification
|1. Siltation from agricultural and urban activities||Threat Information|
|Threat Category||Habitat Loss or Degradation||Extent||Widespread|
|General Threat||Agricultural/ Industrial Practices||Occurrence||Historic /Current|
|Specific Threat||Siltation||Causal Certainty||Medium|
|Stress||Reduced population size||Level of Concern||High|
|2. Water quality deterioration from agricultural and urban activities (fertilizers, sewage treatment etc)||Threat Information|
|General Threat||Agricultural/Urban run-off||Occurrence||Historic/Current|
|Specific Threat||Nutrient Loading||Causal Certainty||Low|
|Stress||Toxic effects (reduced productivity, increased mortality)||Level of Concern||Medium|
1.5.2 Description of Threats
The following description of threats in the Thames River is adapted from the draft Recovery Strategy for the Thames River Aquatic Ecosystem (TRRT 2005).
Threat 1: Siltation from agricultural and urban activities
Elevated siltation and turbidity in the Thames River watershed are primarily a result of agricultural practices. Agriculture represents 78% of land use in the upper watershed and 88% in the lower watershed (Taylor et al. 2004). Overland run-off and tile drainage deposit soil directly into drains and waterways. Streamside livestock grazing and ploughing to the waters edge destroys riparian vegetation increasing both erosion rates and the input of sediments (Bailey and Yates 2003).
Areas within the ThamesRiver ecosystem with the highest percentages of soil loss contributing to siltation and turbidity levels are the Middle Thames River (21.2%), Mud (19.9%) and Reynolds (26.4%) sub-watersheds (TRRT 2005). These sub-watersheds are all upstream of former gravel chub collection sites.
Threat 2: Water quality deterioration from agricultural and urban activities (fertilizers, sewage treatment etc)
Nutrients such as nitrogen and phosphorous enter the Thames River system through manure and fertilizer spreading, manure spills, sewage treatment effluent and faulty domestic septic systems (Taylor et al. 2004). High nutrient loadings in the river can often be attributed to livestock manure spreading practices (UTRCA 1998). Fifteen sewage treatment plants with varying treatment levels currently discharge wastewater into the Thames River. Bacteria levels (an indicator of manure and human waste in the water) are often well above provincial recreational standards (100 E.coli/100 ml). Algal blooms can result from high levels of nitrogen and phosphorous in the water. Algal bloom die-offs can reduce dissolved oxygen levels and cause fish kills. Manure spills have been the leading cause of fish kills in Ontario since 1988 (UTRCA 1998). In the Upper Thames River watershed, episodic fish kills are often reported as a result of chemical spills (most frequently oil and fuel).
1.6 Actions Already Completed or Underway
ThamesRiver Ecosystem Recovery Strategy: The Thames River Recovery Team (TRRT), formed in 2002, is in the process of finalizing an ecosystem-based recovery strategy for the aquatic species at risk (SAR) in the Thames River. The long-term recovery goal of the TRRT is “to use an ecosystem approach to stabilize and improve SAR populations within the Thames River ecosystem and to reduce or eliminate threats to these species and their associated habitats, so that their long-term viability in the watershed is ensured” (TRRT 2005). The gravel chub, along with 23 other COSEWIC-listed species (7 mussels, 6 reptiles, 10 fishes) that either historically inhabited or currently inhabit the Thames River watershed, are the focus of the recovery strategy. Action plans put forward by the TRRT would increase the probability of there being suitable habitat available for the gravel chub should re-introductions take place.
1.7 Knowledge Gaps
Survey Requirements: Prior to developing re-introduction plans, should this be deemed feasible, it is necessary to confirm through intensive, targeted sampling that gravel chub are no longer present. To be consistent with past sampling efforts, targeted sampling should occur during the same months and utilize seine nets and electro-fishing gear (backpack and boat). As the last specimens of gravel chub collected from the Thames River in 1958 were from trawls, the use of fine-mesh trawl nets should also be attempted.
Biological/Ecological Research Requirements: Information on the life history characteristics of the gravel chub is required to refine recovery approaches and to define residence, if appropriate, and critical habitat.
Threat Clarification Research Requirements: The threats facing the gravel chub need to be evaluated in terms of their specific impact on the species.
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