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Recovery Strategy for the Northern Madtom (Noturus stigmosus) in Canada (Proposed)

1. Background

1.1 Species Assessment Information from Committee on the Status of Endangered Wildlife in Canada (COSEWIC)

Common Name: Northern Madtom

Scientific Name: Noturus stigmosus

Current COSEWIC Status & Year of Designation: Endangered (2002)

Reason for Designation: This species has a very restricted Canadian range (two extant locations), which is impacted by deterioration in water quality and potential negative interactions with an exotic species, the Round Goby (Neogobius melanostomus). One population (Sydenham River) has been lost since 1975.

Canadian Occurrence: Ontario

COSEWIC Status History: Examined in April 1993 and placed in the Data Deficient category. Re-examined in April 1998 and designated Special Concern. Status re-examined and uplisted to Endangered in November 2002. Last assessment was based on an existing status report with an addendum.

1.2 Description

The following description is adapted from Holm and Mandrak (1998). The Northern Madtom (Noturus stigmosus Taylor, 1969) is a small (132 mm, maximum total length) catfish (Ictaluridae) recognized by an overall mottled colour pattern with three distinct saddle-shaped markings on the back, located at the front of the dorsal fin, behind the dorsal fin and at the adipose fin (Figure 1). Two pale spots that are smaller than the diameter of the eye are usually present anterior to the dorsal fin. The dorsal and adipose fins possess pale edges while three to four irregular crescent-shaped bars are present on the caudal fin, with the middle bar typically extending across the upper and lower caudal rays and touching the caudal peduncle. Reproductive males will develop a flattened head, diffusion of dark pigments and conspicuous swellings behind the eyes, on the nape and on the lips and cheeks. The Northern Madtom is most often confused with the Brindled Madtom (N. miurus), which lacks pale edges on the dorsal and adipose fins, has a black tip on the dorsal fin, and has a shallower notch between the adipose fin and the tail (Holm et al. 2009).

No subspecies of Northern Madtom have been recognized (Holm and Mandrak 1998); however, Mayden et al. (1992; cited in Holm and Mandrak 1998) suggested that it might be polytypic which may warrant its separation into several species. The Northern Madtom underwent a taxonomic revision and a new species (N. gladiator) was described from populations of the Coastal Plain in Kentucky and Tennessee (Thomas and Burr 2004). In a study examining the phylogenetic relationships among Noturus spp., Hardman (2004) compared nucleotide sequences from Northern Madtom populations above and below (now considered to be N. gladiator [Thomas and Burr 2004]) the Fall Line (a low east-facing cliff that parallels the Atlantic coastline from New Jersey to the Carolinas) and found them to be genetically less than 1% different, despite being morphologically differentiable. It is important to note that Canadian specimens were not included in these taxonomic studies.

Figure 1. The Northern Madtom (Noturus stigmosus). © 1996 Joseph R. Tomelleri.

Figure 1. Northern Madtom © 1996 Joseph R. Tomelleri. (See long description below)
Long description of Figure 1

Figure 1 is captioned “The Northern Madtom (Noturus stigmosus)”. The figure shows a coloured line drawing of the Northern Madtom, scientific name Noturus stigmosus. The drawing is by Joseph R. Tomelleri.

1.3 Populations and distribution


Global Range

The Northern Madtom is native to North America and has a disjunct distribution throughout parts of the Mississippi and western Lake Erie and Lake St. Clair drainages (Figure 2). It is found in several tributaries of the Mississippi drainage system in Tennessee. It is also present throughout most of the Ohio River basin in Indiana, Kentucky and Ohio, as well as in restricted areas of Illinois, Pennsylvania and West Virginia. In the western basin of Lake Erie, the Northern Madtom is found in several tributaries in Indiana, Michigan and Ohio, as well as in Lake St. Clair and the Detroit and St. Clair rivers, which form the border between Michigan and Ontario (Holm and Mandrak 2001).

Figure 2. Global range of the Northern Madtom.

Figure 2. Global range of the Northern Madtom. (See long description below)
Long description of Figure 2

Figure 2 is captioned “Global range of the Northern Madtom”. The map shows 4 areas, 2 areas are large and 2 areas are small. One large area starts in the middle of Illinois, moves east through the upper half of Indiana through the lower portion of Michigan encompasses Lake St. Clair and into Ontario. The second large area starts in the middle of Kentucky, includes the lower border of Indiana, the southwest portion of Ohio and the northwest portion of West Virginia. The third area is the smallest and is half in Illinois and half in Kentucky. The final area is also small and lies entirely within Pennsylvania in the northwest corner of the state.

Canadian range

In Canada, the Northern Madtom is known only from Lake St. Clair and the Detroit, St. Clair, Sydenham and Thames rivers (Figure 3). The species is believed to be extirpated from the Sydenham River (Holm and Mandrak 1998).

Percentage of global distribution in Canada

It is likely that less than 5% of the species global range occurs in Canada.

Distribution trend

The change in the distribution of the Northern Madtom is difficult to assess due to a lack of sampling data. It is unclear whether new records of the species (since it was first reported in Canada in 1963) are a result of a range expansion or more intensive sampling (Holm and Mandrak 1998).

Figure 3. Canadian range of the Northern Madtom.

Figure 3. Canadian range of the Northern Madtom. (See long description below)
Long description of Figure 3

Figure 3 is captioned “Canadian range of the Northern Madtom”. The map shows southwest Ontario. Individual data points are identified by year of capture. The map shows Northern Madtom have been found in Thames River, St. Clair River and Detroit River since 2001. Previous to this, the Northern Madtom was also found in Lake St. Clair.

Population size and status

Global population size and status

The Northern Madtom is considered to be rare to extremely rare throughout its range (Table 1) and has a global status rank of vulnerable (NatureServe 2009). The species is considered critically imperilled in Illinois, Indiana, Michigan, Ohio and West Virginia. In Pennsylvania and Kentucky the Northern Madtom is considered imperilled and imperilled/vulnerable, respectively. It has not been assigned a rank in Arkansas (NatureServe 2009). The global short-term trend of Northern Madtom populations is estimated as declining to stable (± 10% fluctuation to 30% decline) (NatureServe 2009).

Table 1. Canadian and U.S. national and provincial/state heritage status ranks for the Northern Madtom (NatureServe 2009)
Canada and U.S. National Rank (NX)Provincial/State Rank (SX)
Canada (N1N2)Ontario (S1)
United States (N3)Arkansas (SNR), Illinois (S1), Indiana (S1), Kentucky (S2S3), Michigan (S1), Ohio (S1), Pennsylvania (S2), West Virginia (S1)

Canadian population size and status

In Canada, the Northern Madtom occurs within an area less than 1600 km² and occupies an area less than 700 km² (COSEWIC 2002); however, this does not include the recently confirmed St. Clair River record.

Lake St. Clair, Detroit River, St. Clair River

The first recorded occurrence of the Northern Madtom in Canada was a single specimen that was trawled from Lake St. Clair, near the outlet into the Detroit River, in 1963 (Trautman 1981). Although it was not recorded from Canada until 1963, it is likely that Northern Madtom has always been present but went undetected because it is a cryptic species. Additionally, the species is found in areas that are difficult to sample as a result of accessibility issues and the nature of the habitat (e.g., swift-flowing, deep, waters). In 1996, three juveniles were seined at night along the south shore of Lake St. Clair at the mouth of the Belle River (Holm and Mandrak 2001) and a single individual was found dead near the mouth of Pike Creek (Royal Ontario Museum [ROM], unpubl. data). The most recent Canadian record for Northern Madtom in Lake St. Clair is from 1999 when one specimen was captured incidentally by a commercial fisherman off of Walpole Island.

In 1994, a single Northern Madtom was caught near the original capture site on the Canadian side of the Detroit River (Holm and Mandrak 1998) and in 1996 approximately 50 specimens were either observed or collected around Peche Island in the Detroit River. In 2008, a total of 214 Northern Madtom were captured in the Detroit River during a mark-recapture study conducted by a graduate student with the United States Geological Survey (USGS); 145 specimens were captured on the American side of the river adjacent to Belle Isle and 69 specimens, including four young-of-the-year (YOY), were captured on several occasions (from one site) on the Canadian side near Peche Island (B. Daley, USGS, unpubl.data). One individual originally captured and marked at Belle Isle was recaptured almost a mile upstream near Peche Island (B. Daley, unpubl. data).

Preliminary results of sampling conducted at Fighting Island in 2009 indicate that Northern Madtom is present at this location, which is approximately 20 kilometres downstream of Peche Island. Seven specimens (102-126 mm TL) were captured in minnow traps at artificial spawning shoals created for Lake Sturgeon (Acipenser fulvescens) (United States Fish and Wildlife Service [USFWS], unpubl. data). Holm and Mandrak (2001) suggested that the lack of Canadian records in the Detroit River and Lake St. Clair between 1963 and 1994 probably resulted from the limited amount of trawling and night sampling conducted, as well as errors in species identification.

Sampling (day and night trawls, and day and night seining) by the ROM in 1996 failed to capture or observe the Northern Madtom on the Canadian side of the St. Clair River; however, sampling conducted by Fisheries and Oceans Canada (DFO) in 2003 yielded a juvenile (suggesting successful reproduction) downstream of the Lambton Generating Station at the confluence of Clay Creek. Northern Madtom records exist for the American side of the St. Clair River; it was last recorded in 1995, when several larvae, YOY and adult specimens were captured (Carman 2001).

Thames River and Sydenham River

In July 1991, a specimen was captured by the ROM in the Thames River near Wardsville, and a juvenile Northern Madtom was captured at the same location in August 1997 (Holm and Mandrak 2001). From 2003 to 2008, juvenile and adult Northern Madtom were captured incidentally by graduate students conducting research on the Eastern Sand Darter (Ammocrypta pellucida). The majority of specimens were captured in the vicinity of Big Bend Conservation Area, located upstream of Wardsville. Targeted sampling for the Northern Madtom conducted in 2008 by DFO failed to capture any specimens; however, the species was captured incidentally in 2008 near Big Bend (A. Dextrase, Ontario Ministry of Natural Resources (OMNR), pers. comm. 2009).

A specimen originally identified as a Brindled Madtom caught in 1975 in the Sydenham River near Florence, was re-examined by the ROM in 1999 and identified as a Northern Madtom. Although it is possible that this specimen was the result of an introduction (e.g., bait-bucket release), it is more likely representative of an established population in the Sydenham River due to the proximity of other confirmed records within the Lake St. Clair watershed (i.e., Thames River and Lake St. Clair). No specimens have been recorded from the Sydenham River since 1975, despite repeated sampling in the same locale (Holm and Mandrak 1998); thus, it is likely that if there was an established population in the river, it is now extirpated.

Percent of global abundance in Canada

The percentage of the species’ global abundance in Canada is unknown; however, it is likely to be less than 5%.

Population trend

The presence of juveniles in Lake St. Clair, the Detroit River, the St. Clair River and the Thames River, indicates that reproduction is presently occurring; however, the lack of short- and long-term population abundance and demographic data in Canada greatly limits our ability to properly assess population trends and stability.

1.4 Needs of the Northern Madtom

1.4.1 Habitat and biological needs

Spawn to Hatch

Northern Madtom are cavity nesters, building nests in depressions under large rocks and in debris such as bottles, cans and boxes (Etnier and Starnes 1993, Goodchild 1993, Holm and Mandrak 1998, MacInnis 1998). Taylor (1969) observed that, in Michigan, the Northern Madtom reproduced earlier than the Brindled Madtom, and that clutch sizes were larger, ranging from 61 to 141 eggs. In Michigan, spawning occurs in mid- to late-July, similar to a population in the Canadian portion of Lake St. Clair (MacInnis 1998). Northern Madtom were observed and video recorded by MacInnis (1998) at one site (near Sandpoint Beach, close to the outflow into the Detroit River) in Lake St. Clair between 17 July and 13 August 1996, while conducting a study on Round Goby (Neogobius melanostomus) reproduction using artificial nest cavities. During this time, gravid Northern Madtom and recently spawned eggs were observed in the artificial cavities, and male Northern Madtom were observed guarding both eggs and newly hatched larvae. MacInnis (1998) concluded that reproduction in the Northern Madtom likely occurred over a one-month period and that males provided sole parental care of eggs, larvae and juveniles. Nests consisted of a small depression dug into the substrate under the artificial cavity and eggs were laid as a single mass. Fecundity was conservatively estimated as 32, 85 and 140 eggs for three separate egg masses (MacInnis 1998), a relatively low number; as a group, madtoms are one of the least fecund oviparous fishes in North America (Burr and Stoeckel 1999). MacInnis (1998) also proposed that the larger egg masses represented the spawning efforts of more than one female; however, this was not directly observed. Incubation time was estimated at five to ten days and YOY were measured at approximately 30 mm TL before their first winter (MacInnis 1998). The spawning sites in Lake St. Clair had substrates of sand and/or cobble and were surrounded by dense aquatic vegetation. Water depths ranged from 1.5 to 1.8 m, water temperature was approximately 23°C and there was a noticeable current flowing west into the Detroit River (MacInnis 1998). There is no information regarding the spawning habitat characteristics for the Northern Madtom in the Thames River.

Young-of-the-Year (YOY)

There is almost no published information on the habitat requirements of YOY Northern Madtom. In Lake St. Clair, larvae were observed in nests being guarded by the male in August and were observed taking cover in surrounding vegetation when the nests were removed (MacInnis 1998); therefore, it is likely that they require some sort of structure to provide cover. In the Thames River, YOY have been captured from shallow (< 2 m) sandbars that had little flow (M. Finch, University of Waterloo, unpubl. data) as well as areas containing substrates of fine gravel (mean size 2-8 mm) and moderate flow (0.3 m/s) (A. Dextrase, Ontario Ministry of Natural Resources [OMNR], unpubl. data). The YOY of two related species, the Brindled Madtom and Tadpole Madtom (N. gyrinus), are typically found in shallow waters (0-2 m) over substrates of sand, mud and silt, with aquatic vegetation (Goodyear et al. 1982, Lane et al. 1996b).

Juvenile (age 1 until sexual maturity [2 yrs])

The habitat requirements of juvenile Northern Madtom are unknown; however, a juvenile specimen was collected from the same site as an adult specimen in the Thames River (Holm and Mandrak 1998), suggesting that adult and juvenile habitat requirements are the same or similar.


Goodchild (1993) noted that small and sporadic populations suggest that the Northern Madtom has very specific ecological requirements and thus is probably intolerant of habitat degradation. However, more recent evidence suggests that the species tolerates a wide range of habitat conditions (Dextrase et al. 2003). It can be found in small creeks to large rivers, with clear to turbid water and moderate to swift current over substrates consisting of sand, gravel and rocks, occasionally with silt, detritus and accumulated debris. Although the species is somewhat tolerant of turbidity, it is believed to avoid extremely silty situations (Goodchild 1993). It is also occasionally associated with macrophytes, such as stonewort (Chara spp.) (Holm and Mandrak 2001). The Northern Madtom has been sampled at depths ranging from less than 1 m to 7 m, where it was either seined or trawled during the day and/or night. For example, two specimens were collected in the Thames River, which is very turbid (Secchi depth < 0.2 m), over a substrate consisting of sand, gravel and rubble, and devoid of silt or clay (Holm and Mandrak 2001). Other abiotic characteristics of the site also included a moderate current, maximum depth of 1.2 m, water temperature of 23-26°C, conductivity of 666 μS and a pH of 7.9 (Holm and Mandrak 2001). Sexual maturity in the Northern Madtom is believed to be reached at approximately two years of age (Taylor 1969).

The Northern Madtom is likely an opportunistic feeder with a diet consisting mainly of chironomids, mayflies, caddisflies, small fishes and crustaceans (Holm and Mandrak 2001). A gut analysis study by French and Jude (2001) found the gut contents of juvenile Northern Madtom to consist mostly of Diptera and Ephemeroptera. The Northern Madtom is very secretive and likely to be a nocturnal feeder (Goodchild 1993) and spawner (Coad 1995).

1.4.2 Ecological role

The Northern Madtom is a nocturnal, benthic feeder, and gut contents demonstrate its reliance on small benthic invertebrates, such as chironomids, mayflies and caddisflies, as well as small fishes and crustaceans. Other benthic fishes, such as other madtoms (Noturus spp.), gobies (Round Goby, Tubenose Goby [Proterorhinus marmoratus]) and sculpins (Cottus spp.), may directly compete with the Northern Madtom for these food sources.

1.4.3 Limiting factors

The Northern Madtom may be limited by several life-history traits which include: minimal temperature for spawning; spawning habitat requirements; and, fecundity and maximum age. Populations of Northern Madtom in Canada appear to be at the northern edge of the species’ distribution, which is limited by an estimated minimal spawning temperature of 23°C (Taylor 1969, MacInnis 1998). The Northern Madtom is a cavity spawner, thus the availability of suitable spawning habitat (silt-free cavities in substrate or under debris/rocks/logs) may also pose a limitation to the species. Competition for suitable spawning sites is likely to occur with the Brindled Madtom and potentially with the Round Goby; however, direct competition has yet to be documented (MacInnis 1998, Holm and Mandrak 2001). Although strong parental care (via nest-guarding) is provided by the male Northern Madtom, there is limited knowledge of the species’ ability to compete for nest sites. Additional research is needed to clarify the role of interspecific competition on reproductive success. The Northern Madtom is a relatively short-lived species, with a maximum reported age of approximately two to three years (Taylor 1969) and likely spawns only once or twice in its lifetime (inferred from Burr and Stoeckel 1999). However, it should be noted that populations of many fishes at the northern limit of their range typically have longer life spans – this may also be the case for the Northern Madtom in Canada.  As suggested by Simonson and Neves (1992), relying on only one or two cohorts for reproduction each year could jeopardize the long-term stability of some small madtom populations. This, combined with the low fecundity of the Northern Madtom, may limit the population potential of the species.

1.5 Threats

The threats identified for the Northern Madtom are considered to be potential threats as they have not been demonstrated empirically. Thus, the following discussion is based primarily on assumption and/or plausible cause.

1.5.1 Threat classification

Threats believed to be affecting the Northern Madtom are listed by waterbody in Table 2. Seven potential threats were ranked by the recovery team based on their expected relative impacts, spatial extent and expected severity. The threat classification parameters are defined as follows:

spatial extent of the threat in the waterbody (widespread/localized)
the frequency with which the threat occurs in the waterbody (seasonal/continuous)
Causal certainty
the level of certainty that it is a threat to the species (High – H, Medium – M, Low - L)
the severity of the threat in the waterbody (H/M/L)
Overall level of concern
composite level of concern regarding the threat to the species, taking into account the four parameters listed above (H/M/L).
Table 2. Threat classification table for Northern Madtom
PopulationSpecific threatExtent (widespread/localized)Frequency (seasonal/continuous)Causal certainty
(high, medium, low)
(high, medium, low)
Overall level of concern
(high, medium, low)
Thames RiverSiltationWidespreadContinuousMediumHighHigh
Thames RiverTurbidityWidespreadContinuousLowHighHigh
Thames RiverNutrient loadingsWidespreadContinuousMediumHigh/MediumHigh
Thames RiverExotic speciesLocalizedUnknownMediumLow (increasing)High
Thames RiverToxic compounds (pesticides/herbicides)LocalizedSeasonalMediumMediumMedium
Thames RiverPhysical habitat lossLocalizedContinuousMediumExtremely LowExtremely Low
Detroit River/Lake St. ClairSiltationLocalizedContinuousMediumLow/MediumMedium
Detroit River/Lake St. ClairTurbidityWidespreadContinuousLowLowLow
Detroit River/Lake St. ClairNutrient loadingsWidespreadContinuousMediumMedium/HighMedium?
Detroit River/Lake St. ClairExotic speciesWidespreadContinuousMediumHighHigh
Detroit River/Lake St. ClairToxic compoundsDetroit River -  Widespread; Lake St. Clair – LocalizedContinuousMediumHighHigh
Detroit River/Lake St. ClairPhysical habitat lossLocalizedContinuousMediumHighHigh
St. Clair RiverSiltationLocalizedContinuousMediumLow/MediumMedium
St. Clair RiverTurbidityWidespreadContinuousLowLowLow
St. Clair RiverNutrient loadingsWidespreadContinuousMediumMedium/HighMedium?
St. Clair RiverExotic speciesWidespreadContinuousMediumHighHigh
St. Clair RiverToxic compoundsWidespreadContinuousMediumHighHigh
St. Clair RiverPhysical habitat lossLocalizedContinuousMediumHighHigh
All populationsClimate changeWidespreadContinuousHighLowLow

1.5.2 Description of threats

Habitat loss and degradation

Siltation and turbidity

An increase in suspended sediments leads to increased turbidity, decreased light penetration and lower primary productivity. High rates of sediment deposition can alter the composition of gravel and cobble habitats, thus impacting the quality and availability of fish habitat (Bailey and Yates 2003). The impacts of high sediment loading on the Northern Madtom are not fully understood. The species has been collected from highly turbid waters, such as the Thames River, suggesting that the species has some level of tolerance to turbidity. However, the Northern Madtom is no longer found in the turbid Sydenham River, which is located in an intensive agricultural landscape (Holm and Mandrak 1998) (assuming there was a population in the Sydenham River). It is unclear whether the Northern Madtom is primarily impacted by suspended sediments in the water column or excessive sediment deposition on the substrate; however, it seems likely that high rates of silt deposition could affect the species ability to nest in cavities (Dextrase et al. 2003, The Thames River Recovery Team [TRRT] 2005). Silt deposition may also indirectly impact the Northern Madtom through a potential reduction in their invertebrate food supply.

Direct soil deposits through agricultural tile drainage systems and overland runoff have the greatest influence on siltation rates (Bailey and Yates 2003). Furthermore, channelization and loss of riparian zones along lakes and watercourses increases the level of sediment input, as well as the rate of streambank and shoreline erosion. Livestock grazing and ploughing to the edge of a watercourse destroys riparian vegetation, thus impacting rates of silt deposition into adjacent watercourse (Bailey and Yates 2003). In the United States, channelization is the most serious threat facing the Northern Madtom, followed closely by increased siltation and turbidity (NatureServe 2009).

Nutrient loading

Increased nutrient loading can have an impact on water quality and may have direct and indirect effects on the Northern Madtom. Nutrient loading, especially of phosphorus and nitrogen, from agricultural fertilization and manure use practices, as well as effluents from sewage treatment plants and faulty septic systems, can adversely affect habitat quality. Such negative impacts may include increased turbidity, increased occurrence of harmful algal blooms, disruption of food webs and increased macrophyte growth (Bailey and Yates 2003). In the Thames River, phosphorous levels at most sites in the watershed have shown a gradual downward trend since the 1970s; however, levels remain above provincial guidelines of 30 µg/L for the protection of aquatic life (The Thames River Ecosystem Recovery Team [TRERT] 2004). From the period covering 2001-2006, the median total phosphorous concentration in the Thames River was 113 µg/L, second only to the Don River in Ontario for total phosphorous levels (Ontario Ministry of the Environment 2009). Additionally, mean nitrite/nitrate values in the Thames River watershed were over the recommended limits from 1991-2000, and nitrate levels have shown an increasing trend in the watershed over the past 30 years (TRERT2004).

Physical habitat loss

Physical habitat loss is one of the leading threats to aquatic species at risk (Dextrase and Mandrak 2006), and this is likely the case for the Northern Madtom. Habitat loss from dredging, as well as lake and river shoreline modifications (e.g., shoreline hardening projects, piers, docks, marinas) along the Detroit River and Lake St. Clair, is a significant and ongoing concern.

Toxic compounds

The effects of toxic compounds on the Northern Madtom are currently unknown. The species is found in the Detroit and St. Clair Rivers which have both been designated as an Area of Concern (AOC). An AOC is a severely degraded geographic area within the Great Lakes Basin with known impairments of beneficial water use that can impact the area’s ability to support aquatic life (Great Lakes Information Network 2009). Beneficial use impairments have been identified in the St. Clair River (10 impairments) and the Detroit River (11) as a result of urban and industrial development, bacteria, PCBs, PAHs, metals, oils and greases (U.S. Environmental Protection Agency 2009). In the Thames River, pollutants may include pesticides from agricultural and urban areas, chloride (e.g., from road salt, wastewater treatment and water softeners) and metals (TRERT 2004). Over the past 30 years, chloride levels in the Thames River have increased continually at sites across the watershed, but in most cases remain below the Environment Canada guidelines for sensitive aquatic species (TRERT 2004). In the United States, chemical run-off from agricultural and urban sources is one of the major threats facing Northern Madtom (NatureServe 2009). A related species, the Neosho Madtom (N. placidus), appears to be limited by the presence of heavy metals such as cadmium, lead and zinc (Wildhaber et al. 2000).

Further investigation is required to identify the impacts of pollutants and to fully understand the type and extent of stress exerted upon Northern Madtom populations in Canada.

Exotic species

The negative impacts of exotic species on native fishes in the Great Lakes basin have been well documented (e.g., French and Jude 2001, Thomas and Haas 2004). Exotic species may affect the Northern Madtom through direct competition for space and habitat, food, spawning sites and through the restructuring of aquatic food webs. The occurrence of the Round Goby has been implicated in the decline of the Mottled Sculpin (Cottus bairdii) and the Logperch (Percina caprodes) in the St. Clair River (French and Jude 2001). Given the ecology of the Round Goby, it could, potentially, directly compete with the Northern Madtom for food and habitat (MacInnis 1998, Jansen and Jude 2001). The Round Goby could also directly compete with Northern Madtom for spawning sites; however, the Northern Madtom would likely not be as vulnerable to competition for spawning sites as the spawning seasons of the two species barely overlap (MacInnis and Corkum 2000). Although the Round Goby has been found in the lower reaches of the Sydenham and Thames rivers, recent sampling on both rivers has documented considerable upstream movement in 2007 to areas where it had not previously been found (A. Dextrase, pers. comm., 2007, M. Poos, University of Toronto, pers. comm., 2007). In the Sydenham River, the Round Goby has been confirmed in the mid-reaches, just 3 km downstream from the town of Florence. The impacts of the exotic Zebra Mussel (Dreissena polymorpha) and Quagga Mussel (D. bugensis) on the Northern Madtom are unknown but may negatively impact the species by colonizing potential nesting cavities as well as altering food web dynamics and surrounding water quality.

Further research on the impacts of exotic species including Zebra and Quagga mussels, on the Northern Madtom in the Detroit River – St. Clair River corridor, as well as in the Sydenham and Thames rivers is required to provide recovery planners with better tools to manage and understand the Northern Madtom within these systems.

Climate change

Climate change is expected to impact the Northern Madtom and other fishes at risk in southwestern Ontario (Essex-Erie Recovery Team [EERT] 2008). Several impacts related to climate change are expected to impact aquatic communities of the Great Lakes basin, including: increases in water and air temperatures; changes in water levels; shortening of the duration of ice cover; increases in the frequency of extreme weather events; emergence of diseases; and, shifts in predator-prey dynamics (Lemmen and Warren 2004). The effects of climate change will be widespread and should be considered a contributing impact to species at risk and all habitats. While it is possible that some species, including the Northern Madtom, may benefit initially from the effects of climate change through possible northern range expansions, a suite of reactions related to expected changes in evaporation patterns, vegetation communities, decreased lake levels, increased intensity and frequency of storms, and decreases in summer stream water levels may offset the direct benefits of increased water temperatures (EERT 2008).

1.6 Actions already completed or underway

Ecosystem recovery strategies:  The following aquatic ecosystem-based recovery strategies include the Northern Madtom and are currently being implemented by their respective recovery teams. Each recovery team is co-chaired by DFO and a Conservation Authority and receives support from a diverse partnership of agencies and individuals. Recovery activities implemented by these teams include active stewardship and outreach/awareness programs to reduce identified threats; for further details on specific actions currently underway, please refer to the approaches identified in Table 6. Funding for these actions is supported by Ontario’s Species at Risk Stewardship Fund and the government of Canada’s Habitat Stewardship Program for Species at Risk. Additionally, research requirements for species at risk identified in recovery strategies are funded, in part, by the federal Interdepartmental Recovery Fund.  

Essex-Erie Region Fishes - The Essex-Erie region is located on the north shore of Lake Erie and is bordered to the east by the Grand River watershed, to the west by the Detroit River and to the north by the Lake St. Clair and Thames River watershed. The long-term goal of this strategy is “to maintain and restore ecosystem quality and function in the Essex-Erie region to support viable populations of fish species at risk, across their current and former range” (EERT 2008).

SydenhamRiver Ecosystem - The long-term goal of this strategy is “to sustain and enhance the native aquatic communities of the Sydenham River through an ecosystem approach that focuses on species at risk” (Dextrase et al.2003).

ThamesRiver Ecosystem - The goal of this strategy is to develop “a recovery plan that improves the status of all aquatic species at risk in the Thames River through an ecosystem approach that sustains and enhances all native aquatic communities” (TRRT 2005).

WalpoleIsland Ecosystem Recovery Strategy: The Walpole Island ecosystem recovery team was established in 2001 to develop an ecosystem-based recovery strategy for the area containing the St. Clair delta, the largest freshwater delta in the world, with the goal of outlining steps to be taken to maintain or rehabilitate the ecosystem and species at risk (Bowles 2005). This recovery strategy includes several fishes at risk, including the Northern Madtom. The recovery goal of the Walpole Island ecosystem recovery strategy is “to conserve and recover the ecosystems of the Walpole Island Territory in a way that is compliant with the Walpole Island First Nation Environmental Philosophy Statement, provides opportunities for cultural and economic development and provides protection and recovery for Canada’s species at risk” (Bowles 2005).

Remedial action plans (RAPs):  RAPs have been developed for the Detroit River AOC and the St. Clair River AOC to guide restoration and protection efforts. RAPs proceed through three stages: 1) Determination of severity and causes of environmental degradation; 2) Identification of goals, recommendation of actions that will lead to protection and restoration of ecosystem health; and, 3) Implementation of recommended actions and progress towards restoration and protection efforts measured (Environment Canada 2008a). There are 45 and 104 recommended remedial actions for the St. Clair River AOC and Detroit River AOC, respectively, and many of these have already been implemented (Environment Canada 2008b,c).

Recent surveys: Table 3 summarizes recent fish surveys conducted by various agencies within areas of known occurrence of the Northern Madtom.

Table 3. Summary of recent fish surveys in areas of Northern Madtom occurrence (adapted from EERT 2008)
Waterbody / general areaSurvey description (years of survey)Gear typeNorthern Madtom captured (Yes/No)
Lake St. ClairOMNR nearshore fish community survey (2005 and 2007-2010; south shore)seine
Lake St. ClairOMNR nearshore fish community survey (2007; south shore)boat electrofishing
Lake St. ClairMichigan Department of Natural Resources (DNR) fish community survey (1996-2001; south shore)trawl
Lake St. ClairDFO sampling (2003, 2004; St. Clair NWA)boat electrofishing
Lake St. ClairROM (2001-2002; Walpole Island) 
Lake St. ClairDFO/University of Guelph sampling (2003-2004; Mitchell’s Bay)boat electrofishing, additional gear (fyke nets, trap nets, minnow traps etc)
Detroit RiverDFO/University of Windsor fish-habitat association study (2003-2004)seine, boat electrofishing
Detroit RiverDFO/University of Guelph coastal wetlands study (2004-2005) 
Detroit RiverDFO Area of Concern sampling (2003-2004) 
Detroit RiverMichigan DNR/USFWS/OMNR nearshore fish community sampling (2008)seine, boat electrofishing,additional gear (fyke nets, trap nets, minnow traps etc)
Detroit RiverUSGS Northern Madtom sampling (2008)additional gear (fyke nets, trap nets, minnow traps etc)
Detroit RiverUSFWS sampling (2009)additional gear (fyke nets, trap nets, minnow traps etc)
St. Clair RiverDFO fish community sampling (2003, 2004) 
St. Clair RiverDFO/University of Guelph fish community sampling (2007)boat electrofishing
Thames RiverUTRCA fish SAR survey and gear comparison study 2003 and 2004, upper Thames Riverseine, trawl, backpack electrofishing, boat electrofishing, additional gear (fyke nets, trap nets, minnow traps etc)
Thames RiverDFO/UTRCA fish SAR survey and gear comparison study 2003 and 2004, lower Thames River and lower Thames tributariesseine, trawl, backpack electrofishing, boat electrofishing, additional gear (fyke nets, trap nets, minnow traps etc)
Thames RiverDFO/University of Waterloo lower Thames River Eastern Sand Darter sampling (2006, 2007)seine
Thames RiverDFO/OMNR/Trent University lower Thames River Eastern Sand Darter sampling (2006-2008)seine
Thames RiverDFO targeted Northern Madtom gear comparison survey (2008)seine, trawl, additional gear (fyke nets, trap nets, minnow traps etc)
Sydenham RiverROM non-targeted species at risk sampling (1997)seine
Sydenham RiverDFO/University of Guelph (2002-2003) (including night seining at Florence [historic site])seine, backpack electrofishing

1.7 Knowledge gaps

In Canada, the Northern Madtom has not been thoroughly studied, and, given its rarity and secretive, nocturnal habits, there are numerous aspects regarding its biology, population structure, ecology and life-history traits that remain unknown. This information is required to refine recovery approaches. It is unclear whether a population ever existed in the Sydenham River or whether the single specimen collected was the result of an accidental (bait-bucket or other) introduction. Threat clarification is required, particularly concerning siltation and the impacts of the Round Goby and Zebra Mussel.