Pugnose Minnow (Opsopoeodus emiliae): COSEWIC assessment and status report 2025

Official title: COSEWIC assessment and status report on the Pugnose Minnow (Opsopoeodus emiliae) in Canada

Endangered

2025

COSEWIC assessment summary

Assessment summary – May 2025

Common name: Pugnose Minnow

Scientific name: Opsopoeodus emiliae

Status: Endangered

Reason for designation: This small fish is found in the extreme southwestern part of Ontario. It inhabits rivers and streams, and it is negatively affected by habitat alteration, increasing water temperature, drought, and pollution from nutrient and sediment loading. The revised status since the previous assessment of Threatened reflects the fact that, in the last 10 years, it has been found at only one of the 10 previous sites where it occurred, despite extensive search effort. Continuing declines are likely. This distinctive species is therefore at high risk of extirpation from Canada.

Occurrence: Ontario

Status history: Designated Special Concern in April 1985. Status re-examined and confirmed in May 2000. Status re-examined and designated Threatened in May 2012. Status re-examined and designated Endangered in May 2025.

COSEWIC executive summary

Pugnose Minnow

Opsopoeodus emiliae

Wildlife species description and significance

The Pugnose Minnow (Opsopoeodus emiliae Hay, 1881) is a small (maximum total length 64 mm) member of the family Leuciscidae. The species has a small, upturned mouth, a black lateral band extending from the tail to the snout, and a criss-cross pattern of scaling particularly evident on the upper body. It usually has nine principal dorsal rays, distinct from other Canadian minnows. The Pugnose Minnow represents a monotypic genus. It may be useful as an indicator of aquatic ecosystem health as it often occupies clear vegetated habitats that support a diverse array of taxa.

Aboriginal (Indigenous) knowledge

All species are significant and are interconnected and interrelated. There is no species-specific Aboriginal Traditional Knowledge (ATK) in the report.

Distribution

The Pugnose Minnow is found in the Mississippi River system north to southeastern Wisconsin. Its Canadian distribution is limited to Ontario where it has historically been found in the Detroit and Sydenham rivers and in Lake St. Clair and its smaller tributaries. The Pugnose Minnow is common and widespread in the southern United States where it is found from South Carolina and Florida west to Texas, but is rarer in the northern part of its distribution. In Canada, reports suggest that the species is extirpated from the Thames River system and it has not been detected recently throughout much of the previously reported range, except for the Canard River. Extensive sampling since 2012 indicated persistence of the species in the Canard River (a single location) with ongoing detections until 2021. However, repeated sampling in 2023 and 2024 did not detect any Pugnose Minnow in the Canard River.

Habitat

In Canada, this species occupies turbid, slow-moving or still waters with or without vegetation, woody debris, clay, silt, muck, or sand substrates. In the United States, the Pugnose Minnow prefers clear, slow-moving waters with abundant vegetation.

Biology

The Pugnose Minnow spawns in late May to mid-June. Spawning is believed to take place in shallow areas with submerged and emergent aquatic vegetation over substrates of silt, clay, or sand. However, other sources state that males select and defend a flat surface, such as the underside of a rock, for spawning. Eggs are laid in clusters on the underside of the flat surface and are defended by the male. Nursery habitat is thought to occur in areas with abundant aquatic vegetation and substrates of silt and sand. The Pugnose Minnow feeds on a variety of small insects, crustaceans, filamentous algae and, occasionally, on larval fishes and fish eggs.

Population sizes and trends

The size of the Canadian population of Pugnose Minnow is unknown and existing evidence is insufficient to determine trends in abundance.

In 2010, the Pugnose Minnow was not caught at many of the sites where it had been previously captured, but the species was detected in 2010 in historical collection sites in the East Sydenham River and Little Bear Creek. Targeted sampling for Pugnose Minnow was conducted by Fisheries and Oceans Canada (DFO) in 2010, 2013, 2018, 2019, 2021, 2023, and 2024, which consisted of distribution surveys in the Lake St. Clair drainage in 2010, 2013, 2019, and 2021, and sampling in the Canard River in 2018, 2023, and 2024. Additional targeted sampling in 2013, 2019, and 2021 did not detect the species in most sites where it had been previously collected, including Big Creek, Little Bear Creek, Maxwell Creek, West Otter Creek, and other areas in the lower Sydenham River and Chenail Ecarté. The most recent collection from that watershed was one individual from East Otter Creek in 2003.

Targeted sampling in the Canard River was conducted by DFO in 2018, 2023, and 2024, with many individuals captured in 2018, but no individuals captured in 2023 or 2024. Non-targeted sampling in the Canard River by the University of Toronto in 2017 captured 20 individuals. Non-targeted sampling in the Canard River and other sites was conducted by DFO’s Asian Carp Early Detection Field Surveillance program from 2013 to 2024 (most years), with 108 detections across 11 years, but the most recent detection of Pugnose Minnow from the Canard River by that program occurred in 2021.

Threats

The Canadian population is threatened by climate change and severe weather, pollution, and natural system modifications. The overall threat level was scored as High – Low. Factors that limit the survival of the Pugnose Minnow in Canada remain uncertain. In contrast to most of its range, the Canadian subpopulations occur in turbid environments. Canada’s Recovery Strategy and Action Plan for the Pugnose Minnow identified the overall level of concern for habitat loss and degradation, sediment loading, and nutrient loading as High, and for climate change and exotic species as Medium.

Protection, status, and recovery activities

The Pugnose Minnow is listed as Threatened under Canada’s Species at Risk Act and the province of Ontario’s Endangered Species Act, 2007. Several Canadian and provincial acts protect aquatic species and their habitats in general (for example, the Fisheries Act). The Pugnose Minnow is considered globally Secure (G5) and Imperiled Nationally (N2) and Provincially (S2) in Canada. The Pugnose Minnow is listed as Critically Imperiled (S1) in Michigan, Ohio, and Pennsylvania in the United States. Canada’s Recovery Strategy and Action Plan for Pugnose Minnow concluded that the species’ recovery is biologically and technically feasible.

Technical summary

Opsopoeodus emiliae Hay, 1881

Pugnose Minnow

Petit-bec

Range of occurrence in Canada: Ontario

Demographic information

Generation time (usually average age of parents in the population)

Approximately 1.2 years

Based on previous COSEWIC status report.

Is there an [observed, estimated, inferred, or projected] continuing decline in number of mature individuals?

Yes

Inferred based on lack of detections of the Pugnose Minnow during recent targeted, species-specific sampling at previously occupied sites.

[Observed, estimated, or projected] percent of continuing decline in total number of mature individuals within 3 years [or 1 generation; whichever is longer up to a maximum of 100 years]

Unknown

Historical and present-day population abundance of mature individuals are unknown.

Observed, estimated, or projected] percent of continuing decline in total number of mature individuals within 5 years [or 2 generations; whichever is longer up to a maximum of 100 years]

Unknown

Historical and present-day population abundance of mature individuals are unknown.

[Observed, estimated, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over the last 10 years [or 3 generations; whichever is longer]

Unknown

Historical and present-day population abundance of mature individuals are unknown.

[Projected, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over the next [10 years, or 3 generations, up to a maximum of 100 years]

Unknown

Historical and present-day population abundance of mature individuals are unknown.

[Observed, estimated, inferred, projected, or suspected] percent [reduction or increase] in total number of mature individuals over any period of 10 years [or 3 generations; whichever is longer, up to a maximum of 100 years], including both the past and future (up to a maximum of 100 years in future)

Unknown

Historical and present-day population abundance of mature individuals are unknown.

Are the causes of the decline clearly reversible?

Unknown

Are the causes of the decline clearly understood?

Unknown

More studies are needed to improve knowledge of the life history, population structure, and relative impacts of potential threats on the Pugnose Minnow. Habitat degradation associated with agriculture and urbanization is likely contributing to the observed decline.

Are the causes of the decline clearly ceased?

Unknown

Ongoing degradation of habitat is likely contributing to decline.

Are there extreme fluctuations in number of mature individuals

Unknown

Population size is unknown.

Extent and occupancy information

Estimated extent of occurrence (EOO)

12 km²

In the Canard River upstream of the confluence with the Detroit River. Estimated as 2.65 km², but note must not be smaller than IAO

Index of area of occupancy (IAO), reported as 2 × 2 km grid value

12 km²

Species detections from 2013 to 2024.

Is the population “severely fragmented,” that is, is >50% of individuals or >50% of the total area “occupied” (as a proxy for number of individuals) in habitat patches that are both (a) smaller than required to support a viable subpopulation, and (b) separated from other habitat patches by a distance larger than the species can be expected to disperse?

1. No
2. No

Single location in the Canard River.

Number of “locations”
North Sydenham River – presumed extirpated
Sydenham River (East Branch – presumed extirpated)
East Otter Creek – presumed extirpated
Maxwell Creek – presumed extirpated
Whitebread Drain – presumed extirpated
Little Bear Creek – presumed extirpated
MacDougall Drain – presumed extirpated
Chenail Ecarté – presumed extirpated
Lake St. Clair – presumed extirpated
Detroit River – presumed extirpated
Thames River – presumed extirpated
Canard River (last detection in 2021)

1

Despite extensive, targeted searches in the past 10 years, the Pugnose Minnow has only been collected in the Canard River (tributary of the Detroit River).

Is there an [observed, inferred, or projected] continuing decline in extent of occurrence?

Yes

Observed based on targeted sampling in previously occupied sites.

Is there an [observed, inferred, or projected] continuing decline in area of occupancy?

Yes

Observed based on targeted sampling in previously occupied sites.

Is there an [observed, inferred, or projected] continuing decline in number of subpopulations?

Yes

Observed based on targeted sampling in previously occupied sites.

Is there an [observed, inferred, or projected] continuing decline in number of “locations”?

Yes

Observed based on targeted sampling in previously occupied sites.

Is there an [observed, inferred, or projected] continuing decline in [area, extent and/or quality] of habitat?

Yes

Observed based on targeted sampling in previously occupied sites.

Are there extreme fluctuations in number of subpopulations?

No

Are there extreme fluctuations in number of “locations”?

No

Are there extreme fluctuations in extent of occurrence?

No

Are there extreme fluctuations in index of area of occupancy?

No

Number of mature individuals (by subpopulation)

All

Canard River

Unknown

Total

Unknown

Quantitative analysis

Is the probability of extinction in the wild at least 20% within 20 years [or 5 generations], or 10% within 100 years]

Unknown

Analysis not conducted

Threats

Was a threats calculator completed for this species?

Yes (see Appendix 1)

Overall assigned threat impact: High – Low

Key threats were identified as:

1. 11. Climate change and severe weather (Medium – Low)
2. 9. Pollution (Medium – Low)
3. 7. Natural system modifications (Medium – Low)

Other threats with unknown impacts include: Transportation and service corridors, Agriculture and aquaculture, Biological resource use, Human intrusions and disturbance, and Invasive and other problematic species and genes

What limiting factors are relevant?

• Habitat quality; short lifespan (susceptible to environmental stochasticity); limited dispersal capacity

Rescue effect (from outside Canada)

Status of outside population(s) most likely to provide immigrants to Canada.

Endangered

Assessed as Endangered in U.S. states adjacent to Canadian range. MI (END, S1), OH (END, S1), PA (END, S1)

Is immigration known or possible?

Unknown

Very unlikely, but possible.

Would immigrants be adapted to survive in Canada?

Likely

MI, OH, and PN populations experience similar environmental conditions.

Is there sufficient habitat for immigrants in Canada?

Unknown

Habitat degradation has likely contributed to the presumed decline (and observed reductions in detections), and climate change may reduce future habitat suitability.

Are conditions deteriorating in Canada?

Yes

Habitat degradation/loss to agricultural effects, other land-use development, and climate change.

Are conditions for the source (that is, outside) population deteriorating?

Unknown

Populations in the U.S. that border Ontario are Endangered, but causes are unknown.

Is the Canadian population considered to be a sink?

Unknown

Population structure is not well understood.

Is rescue from outside Canada likely, such that it could lead to a change in status?

Unlikely

Subpopulations of the species occur in adjacent states across from its Canadian distribution. It is possible that individuals may immigrate into Canadian waters. However, due to distance and small body size of the Pugnose Minnow it is extremely unlikely. Additionally, due to the endangered status of adjacent U.S. populations if migration does occur, it is likely that there would not be enough individuals to result in a status change.

Wildlife species with sensitive occurrence data (general caution for consideration)

Could release of certain occurrence data result in increased harm to the Wildlife Species or its habitat?

No

Current status

COSEWIC status history

Designated Special Concern in April 1985. Status re-examined and confirmed in May 2000. Status re-examined and designated Threatened in May 2012. Status re-examined and designated Endangered in May 2025.

Status and reasons for designation

Status: Endangered

Alpha-numeric codes: B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v)

Reason for change in status: I.i; I.iii; III.iii

Reasons for designation: This small fish is found in the extreme southwestern part of Ontario. It inhabits rivers and streams, and it is negatively affected by habitat alteration, increasing water temperature, drought, and pollution from nutrient and sediment loading. The revised status since the previous assessment of Threatened reflects the fact that, in the last 10 years, it has been found at only one of the 10 previous sites where it occurred, despite extensive search effort. Continuing declines are likely. This distinctive species is therefore at high risk of extirpation from Canada.

Applicability of criteria

A: Decline in total number of mature individuals:

Not applicable.

Insufficient data to reliably infer, project, or suspect population trends.

B: Small range and decline or fluctuation

Meets Endangered, B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v)

EOO (12 km²) and IAO (12 km²) are below threshold for Endangered, the population occurs at one location, and is experiencing a continuing decline in EOO, IAO, extent and quality of habitat, number of locations, and number of mature individuals.

C: Small and declining number of mature individuals

Not applicable.

Insufficient data to determine number of mature individuals.

D: Very small or restricted population

Not applicable.

Meets Threatened, D2. Restricted to an IAO of 12 km² (and one location) and prone to substantial decline from effects of human activities or stochastic activities within one to two generations.

E: Quantitative analysis

Not applicable.

Analysis not conducted.

Preface

The Pugnose Minnow remains an enigmatic species—few research articles have been published on its biology since the most recent COSEWIC report completed in 2012. It is presumed extirpated from the Thames River (last observed in 1968) and the MacDougall Drain (last observed in 1984). However, most sites where it had been found in southwestern Ontario, and many adjacent sites, have been sampled since the last report. The Pugnose Minnow has not been captured at any of the sites reported prior to 2013, either in general sampling or through targeted surveys, except for the Canard River where it was most recently collected in 2021. Since the last assessment in 2012, the extent of occurrence has declined by 99% and area of occupancy has declined by 86%. The reasons for the loss of these subpopulations remain unclear, but it is likely related to long-term degradation of habitat conditions in the rivers, associated with agriculture and urbanization. Insufficient sampling has occurred to determine trends in abundance of any of the Canadian subpopulations. Although threats specific to Pugnose Minnow are unknown, the main threats are believed to be climate change effects, degradation of habitat and water quality associated with agriculture and urbanization, and natural system modifications (including invasive and other problematic species)—all ongoing threats within its distribution in Canada.

COSEWIC history

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

Definitions

(2025)

Wildlife species

A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years

Extinct (X)

A wildlife species that no longer exists

Extirpated (XT)

A wildlife species no longer existing in the wild in Canada, but occurring elsewhere

Endangered (E)

A wildlife species facing imminent extirpation or extinction

Threatened (T)

A wildlife species likely to become endangered if limiting factors are not reversed

Special concern (SC)*

A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats

Not at risk (NAR)**

A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances

Data deficient (DD)***

A category that applies when the available information is insufficient (a) to resolve a species’ eligibility for assessment or (b) to permit an assessment of the species’ risk of extinction

*

Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.

**

Formerly described as “Not In Any Category”, or “No Designation Required”

***

Formerly described as “Indeterminate” from 1994 to 1999 or “ISIBD” (insufficient scientific information on which to base a designation) prior to 1994. Definition of the (DD) category revised in 2006.

Wildlife species description and significance

Name and classification

Current classification

Class: Actinopterygii

Order: Cypriniformes

Family: Leuciscidae (formerly Cyprinidae)

Genus: Opsopoeodus

Species: Opsopoeodus emiliae

Subspecies in Canada: N/A

Taxonomic changes since previous report (for reassessments): Family Leuciscidae (formerly Cyprinidae)

Common names

English: Pugnose Minnow

French: petit-bec

Synonyms and notes

Originally described by Hay (1881) in the genus Opsopoeodus, this species was placed in Notropis by Gilbert and Bailey (1972). However, osteological, genetic and behavioural evidence (Campos and Hubbs 1973; Dimmick 1987; Amemiya and Gold 1990; Amemiya et al. 1992; Gold et al. 1992; Johnston and Page 1992; Blanton et al. 2011) suggested that Pugnose Minnow is distinct from Notropis. Eschmeyer (2010) recognized Page and Johnson (1990) as the first publication to reinstate the genus name Opsopoeodus for this species. While Mayden et al. (2006) suggested that Opsopoeodus should be embedded within Pimephales based on cytochrome b sequence data, recent work by Blanton et al. (2011) using both mitochondrial and nuclear sequences confirmed that Opsopoeodus should be considered a distinct genus. The Opsopoeodus genus is most closely related to the genera of Pimephales and Codoma (Stout et al. 2022) and this clade is most closely related to Cyprinella. Gilbert and Bailey (1972) described two subspecies: O. e. peninsularis from the Florida peninsula, and O. e. emiliae occupying the rest of the range including Canada. However, while previously two subspecies were recognized, they have now been designated as synonyms for the single North American species, Opsopoeodus emiliae (Page et al. 2023).

Description of wildlife species

Morphological description

The Pugnose Minnow is a small (maximum total length [TL] of 64 mm; Holm et al. 2022) member of the family Leuciscidae. It has a small, upturned mouth, a black lateral band extending from the tail to the snout, and a criss-cross pattern of scaling particularly evident on the upper body (Holm et al. 2022). The dorsal fin of adult males is dusky or black with a white bar in the middle and the anterior rays of the anal fin are white, both patterns of pigmentation intensify during the spawning season (Holm et al. 2022). Unlike any other Canadian minnow, it usually has nine principal dorsal rays (Scott and Crossman 1973). There are five, ridged pharyngeal teeth in one row on each side (Scott and Crossman 1973). There may occasionally be a fleshy barbel at the posterior end of one or both sides of the lower lip (Gilbert and Bailey 1972). The spawning male develops patches of small tubercles on the snout and chin, a pattern that has been described and figured by Gilbert and Bailey (1972).

The Pugnose Minnow has a small, steeply upturned mouth simiIar to the Golden Shiner (Notemigonus crysoleucas) and Pugnose Shiner (Miniellus anogenus, formerly Notropis anogenus). The Golden Shiner has a more laterally compressed body and has a much longer anal fin with at least 12 anal rays (Holm et al. 2022). The Pugnose Minnow has a dark lateral band that extends onto the nose only, whereas the dark lateral band of the Blackchin Shiner (M. heterodon, formerly Notropis heterodon) and Pugnose Shiner extends onto the nose and chin (Holm et al. 2022). The Pugnose Shiner also lacks the criss-cross scale pattern that occurs on the Pugnose Minnow (Holm et al. 2022).

Designatable units

There is no current evidence to suggest that more than one designatable unit (DU) occurs in Canada. There are no recognized subspecies (O. emiliae) (Gilbert and Bailey 1972; Page et al. 2023). The species occurs in a single biogeographic region (Great Lakes-Upper St. Lawrence) and the genetic population structure is unknown. Using the COSEWIC criteria, a DU is recognized if it is both discrete and evolutionarily significant. Insufficient data for the Pugnose Minnow subpopulations exist to evaluate discreteness or evolutionary significance to establish additional DUs in Canada.

Recognized subspecies or varieties in Canada: N/A

Designatable units (DUs): N/A

Evidence for discreteness: N/A

Evidence for evolutionary significance: N/A

Special significance

The Pugnose Minnow represents a monotypic genus (Stanton et al. 2011) and, as a result, the study of the unique morphology, behaviour, and genetics of this species contributes to our knowledge of the evolution of North American Leuciscidae. Given its propensity for clear, vegetated waters in the main portion of its range (that is, southern United States) (Gilbert and Bailey 1972; Scott and Crossman 1973, Trautman 1981), it may be useful as an indicator of aquatic ecosystem health.

Aboriginal (Indigenous) knowledge

Aboriginal Traditional Knowledge (ATK) is relationship based. It involves information on ecological relationships between humans and their environment, including characteristics of species, habitats, and locations. Laws and protocols for human relationships with the environment are passed on through teachings and stories, and Indigenous languages, and can be based on long-term observations. Place names provide information about harvesting areas, ecological processes, spiritual significance, or the products of harvest. ATK can identify life-history characteristics of a species or distinct differences between similar species.

Cultural significance to Indigenous peoples

There is no species-specific ATK in the report. However, the Pugnose Minnow is important to Indigenous Peoples who recognize the interrelationships of all species within the ecosystem.

Distribution

Global range

The Pugnose Minnow is found in the central United States and southwestern Ontario, Canada (Figure 1, cover illustration). The Pugnose Minnow is more common and widespread in the southern United States where it is found from South Carolina and Florida west to Texas (Figure 1a). It is found in the Mississippi River system northward to southeastern Wisconsin into the Laurentian Great Lakes basin and northeast to southwestern Ontario.

Figure 1a. Global distribution of the Pugnose Minnow. Modified from Page and Burr (1991).

Canadian range

In Canada, the Pugnose Minnow has been known to occur historically in only 11 locations within a small area in southwestern Ontario (Figure 1b), including within the Detroit River, Sydenham River, and Thames River watersheds, and Lake St. Clair. Most historical records were detailed in the 2012 COSEWIC assessment report. The Canadian Museum of Nature also has eight specimens from 1972 and 1979, from the Sydenham River watershed (Table 3; Ilves, pers. comm.).

Figure 1b. Showing all sites where the Pugnose Minnow has been sampled and captured (1935 to 2024). Sites that were sampled without detection of the Pugnose Minnow are shown as open symbols. Note that there are many overlapping open symbols, which may make them appear to be filled. Map created by Ryan Collins, ECCC.

All Pugnose Minnow collected within the last 10 years have been sampled within the Canard River. Between 2015 and 2021, 417 Pugnose Minnow were captured in the Canard River. Of these, 294 were collected from 26 sites during targeted sampling efforts for the species in 2018, which was the largest known collection of this species in Canada (Gáspárdy et al. 2020; Lamothe and Drake 2020). Refer to the section on Population Sizes and Trends for further details.

Population structure

The degree of spatial structure of the Pugnose Minnow subpopulations in Canada is unknown.

Extent of occurrence and area of occupancy

Current EOO

Extent of occurrence (EOO) within Canada is 12 km² (direct estimate is 2.65 km²), calculated using a minimum convex polygon that encompasses known records from 2013 to 2024 (Figure 1c); however, note that the EOO cannot be less than the IAO. This represents a 99% reduction in EOO since the 2012 report (1,254 km²).

Current IAO

Index of area of occupancy (IAO) within Canada is 12 km², calculated using a 2 km × 2 km grid drawn over known records from 2013 to 2024 (Figure 1c). This represents an 86% decline in IAO since the 2012 report (84 km²).

Figure 1c. Enlargement showing all sites where the Pugnose Minnow has been captured in the Canard River between 2013 and 2024. Open symbols identify sites that were sampled without detection of Pugnose Minnow. The squares with dashed lines are the 2 km × 2 km grids outlining the IAO. Map created by Ryan Collins, ECCC.

Fluctuations and trends in distribution

There is no evidence of fluctuations in distribution.

Biology and habitat use

Very little has been written concerning the biology of the Pugnose Minnow in Canada, with the exception of brief generalizations by Parker et al. (1987). Much of the data related to biology and ecology of the Pugnose Minnow have been collected from American sources; however, the Recovery Potential Assessment (Bouvier and Mandrak 2013) and the Recovery Strategy and Action Plan (Fisheries and Oceans Canada 2022) for the species provide an assessment of the Pugnose Minnow in Canada and are the basis for much of the documented information provided in this section (Table 1).

^a Life Stage: stage of the life cycle of the species (for example, seed, egg, seedling, juvenile, larva, pupa, adult).

^b Habitat function: How a habitat supports a life cycle process of the species (for example, habitat that supports spawning, breeding, denning, nursery, rearing, feeding/foraging, migration, flowering, fruiting, seed dispersing, germinating, seedling development).

^c Habitat: The structural or biological features of the area or type of site needed for a species to carry out its life processes.

^d Detail of habitat: Detailed information such as measurable properties or characteristics of the habitat.

Life cycle and reproduction

In Canada, adults are generally 35 to 58 mm total length (TL), not exceeding 64 mm TL (Parker et al. 1987; Holm et al. 2022; Fisheries and Oceans Canada 2022; Gáspárdy et al. 2020). The age or size range at which this species attains sexual maturity is unknown, but is likely one year of age, as is typical with most small fishes.

Spawning behaviour and spawning habitat preferences of the Pugnose Minnow in Canada are not known (Bouvier and Mandrak 2013). However, while evidence suggests that the Pugnose Minnow has a protracted breeding season in Florida, this does not seem to be true for other North American populations (Gilbert and Bailey 1972). Breeding individuals in Arkansas were observed in late May, while gravid females were found in Illinois in mid-June (Gilbert and Bailey 1972). Pugnose Minnow in Missouri was found in spawning condition in early summer (Pflieger 1975). Based on the timing of spawning observed in populations in the northern United States, it is likely that spawning in Canada occurs in spring, between late May to mid-June (Holm et al. 2022). One female (Royal Ontario Museum [ROM] 35781), collected in Mitchell’s Bay on June 2, 1979, had not yet spawned when the water temperature was 21 °C. Spawning is believed to take place at depths of 0 to 2 m in areas with submerged and emergent aquatic vegetation over substrates of silt, clay, or sand (Lane et al. 1996a); however, preferred spawning substrates in Canada are unknown. Similar habitats are thought to provide nursery habitat for the Pugnose Minnow (Lane et al. 1996b).

The egg-clustering and parental care behaviour of the Pugnose Minnow is a complex breeding strategy and, along with Pimephales and Codoma species, is unique among North American minnows. The following account is based primarily on Page and Johnston (1990) and Johnston and Page (1992). Breeding males develop a dark silver-blue body and white tips on the anal and pelvic fins. Patches of tubercles develop on the male’s chin and snout (Gilbert and Bailey 1972). Small white knobs develop on the first three dorsal fin rays and may act as egg mimics to stimulate the female to spawn. Males select a flat surface, such as the underside of a rock, as their spawning site. Based on laboratory observations, the Pugnose Minnow defends its territory from intruders by chasing them from the immediate vicinity of the spawning site. The male exhibits figure “8” circling behaviour at the spawning site and rubs his snout or nape on the surface. The rapid raising and lowering of the male dorsal fin may be used to signal the female to attract her to the nest. Females are led to the spawning site by the males, where the female repeatedly touches the surface of the spawning site with her mouth and snout. The male follows the female, nudging and lifting her abdomen and caudal peduncle with his snout. The spawning act consists of the pair aligning laterally and inverting for about a second. This act is repeated several times, over 6 to 7 days. For the female to deposit the eggs, she inverts so the genital papilla is able to come into contact with the spawning surface. Eggs are laid singly or in strings of 2 to 5 forming a single layer on the underside of the flat surface. Up to 120 eggs are laid per spawning session. The average diameter of the eggs is 1.3 mm. Males defend the nests and eggs from potential predators, and the single layer of eggs allows the male access to the individual eggs. In the laboratory study, eggs hatched in a mean of 142 hours (S.D. = 8.9) at 21 °C. Newly hatched larvae are 5.0 to 5.5 mm TL long (Page and Johnston 1990).

The lifespan of the Pugnose Minnow is approximately 3 years (Parker et al. 1987). Young and Koops (2013) have estimated generation time at 1.2 years. Potential for hybridization is unknown. Population size structure and sex ratios are unknown.

Habitat requirements

Relatively little is known regarding the habitat requirements of Canadian subpopulations of the Pugnose Minnow (Gáspárdy et al. 2020, 2025). It is typically stated that the species prefers clear, slow-moving waters with abundant vegetation (Scott and Crossman 1973; Trautman 1981; Coad 1995), although Parker et al. (1987) collected this species from turbid environments. However, in Canada, the Pugnose Minnow is most often found in habitats with warm, slow-moving, turbid streams with little to no aquatic vegetation (Bouvier and Mandrak 2013). Lamothe and Drake (2020) reported a negative relationship between Pugnose Minnow occupancy and turbidity; however, this species was more likely to occupy clearer water when Wild Celery (Vallisneria americana) was present. The Pugnose Minnow was most likely to be captured at sites in the Canard River where the depth exceeded 0.5 m (Lamothe and Drake 2020).

Other studies have also described observations of the Pugnose Minnow in suboptimal habitat, such as Parker et al. (1981), who collected the species in turbid environments. In 1996 and 1997, the Royal Ontario Museum (ROM) collected Pugnose Minnow from habitats similar to those described by Parker et al. (1987)—Secchi depth was 0.1 to 0.3 m and bottom composition was silt, muck, and detritus with some cover of boulders, woody debris, and aquatic vegetation (Holm, unpublished data).

The Chenail Ecarté and Detroit River species records were from clear, slow-moving side channels with abundant vegetation (Lapointe 2005; DFO, unpublished data). In the Canard River, the Pugnose Minnow was detected at sites with Secchi disk measurements ranging from 0.100 to 0.334 m (min–max) and turbidity measurements ranging between 11.81 and 49.65 NTU (Gáspárdy et al. 2025).

The Pugnose Minnow was caught by DFO in 2003 at 7 sites around the Lake St. Clair drainage, generally with abundant vegetation, silt and clay substrates, high turbidity (Secchi depths ranging from 0.07 to 0.59 m), and summer water temperatures of 18 to 25^oC (Mandrak et al. 2006). In 2010, DFO caught the Pugnose Minnow at 11 sites, with habitat being comprised of either submerged vegetation or open water, silt, and sand substrates, and summer water temperatures ranging from 22 to 30^oC (DFO, unpublished data). The average water depth of the Pugnose Minnow capture was 1.3 m from 2013 to 2019 (DFO, unpublished data).

Therefore, in Canada, this species occupies sites with turbid, slow-moving waters with abundant vegetation, over silt, sand, and clay substrates. It is unclear whether the Canadian population of the Pugnose Minnow’s association with turbid conditions is a long-term adaptation to decrease predation risk from visual predators, or whether the persistence of the Pugnose Minnow is at risk in turbid environments in the absence of nearby habitat with better water quality (Lamothe and Drake 2020).

Movements, migration, and dispersal

It is not known whether the Pugnose Minnow undergoes some degree of migration during spawning or overwintering. Given its small size, it is unlikely that the species migrates or disperses over long distances (Minns 1995).

Interspecific interactions

Diet

The Pugnose Minnow’s upturned mouth suggests it is adapted to feeding on small prey items located within the water column or on the surface of the water. In Ontario, one specimen had adult Diptera and larval Trichoptera in the stomach (Parker et al. 1987). Gut contents of Florida specimens consisted of chironomid larvae, filamentous algae, small crustaceans, larval fishes, and fish eggs (Parker et al. 1987). No studies were found on the diet of the Pugnose Minnow since those reported by Parker et al. (1987). The species’ small mouth limits the size of plant and animal organisms taken.

Predators and competitors

The Pugnose Minnow is likely preyed upon by a variety of fishes. Given its low abundance and occurrence in turbid habitats, it is unlikely that it is a main prey item for piscine or avian predators. In southwestern Ontario, the Pugnose Minnow was often collected at the same sites as the Blackstripe Topminnow (Fundulus notatus) (Mandrak et al. 2006). The Pugnose Minnow was not collected at any of the DFO’s targeted 2019 sampling sites; however, the Pugnose Shiner, Blackstripe Topminnow, Ghost Shiner (Paranotropis buchanani, formerly Notropis buchanani), Gizzard Shad (Dorosoma cepedianum), Brook Silverside (Labidesthes sicculus), Lepomis spp. (young of the year), and Bluegill (Lepomis macrochirus) were collected at sites where Pugnose Minnow were historically sampled (Gáspárdy et al. 2020; Barnucz and Drake 2021).

Physiological, behavioural, and other adaptations

Very little is known regarding the physiology and tolerances of the Pugnose Minnow. Accounts by Scott and Crossman (1973) and Trautman (1981) suggested that the species is sensitive to high levels of turbidity; however, recent sampling efforts have demonstrated that the species is found in turbid habitats. It is unclear whether its presence in turbid habitats in Canada suggests some tolerance to these conditions or that subpopulations are persisting in suboptimal habitats. The method of depositing eggs on the underside of flat objects likely provides some protection to the eggs and emergent fry from siltation (Waters 1995).

Limiting factors

Limiting factors are generally not human-induced and include intrinsic characteristics that make the species less likely to respond to conservation efforts. Limiting factors may become threats if they result in population decline (Table 2). The main limiting factors for the Pugnose Minnow are unknown. However, they may include limited habitat, a relatively short lifespan (making them more susceptible to environmental stochasticity), and poor dispersal ability to avoid known threats.

Population sizes and trends

In 2010, Pugnose Minnow was not caught at many of the sites where it had been previously captured in the East Sydenham River, North Sydenham River, Otter Creek, East Otter Creek, Indian Creek, Whitebread Drain / Grape Run Drain, Little Bear Creek, and Maxwell Creek (DFO unpublished data; Gáspárdy et al. 2025). In 2010 it was detected at five sites in the East Sydenham River (21 individuals) and two sites in Little Bear Creek (11 individuals). Sampling at the above sites subsequent to 2010 has not yielded any Pugnose Minnow (see Abundance section below). Sampling conducted in the Canard River in 2018 captured Pugnose Minnow in that waterbody, with ongoing detections of Pugnose Minnow in the Canard River from 2013 to 2021. Additional targeted sampling by DFO in the Canard River in 2023 and 2024 did not detect Pugnose Minnow. The Natural Heritage Information Centre does not have any recorded observations for this species since 2013.

Data sources, methodologies, and uncertainties

There are insufficient data to estimate population size and trends. Targeted collections at historical localities resulted in the collection of Pugnose Minnow at a single site (Canard River) in 2018. Detection probability for Pugnose Minnow is estimated as 0.44 (44%) per sample, based on a skilled crew using appropriate sampling methods, and sufficient replicate samples (Lamothe and Drake 2020). Targeted and non-target sampling within the historic range of the species has occurred up until 2024, and summarized by site below. Targeted sampling in 2023 and 2024 by DFO was intended to provide a standardized index of population trajectory and abundance; however, no Pugnose Minnow were detected during the 2023 and 2024 sampling efforts (Drake pers. comm.). Additional sampling for Pugnose Minnow has been conducted by DFO targeting historical collection sites (Barnucz and Drake 2021; Gáspárdy et al. 2025) and through general monitoring of watercourses where individuals have been previously collected. Sampling was conducted through a variety of methods including electro-fishing, Mamou trawl, mini-Fyke net, bag seine, and a Missouri trawl. Level of effort varied temporally and among sampling sites. See Table 3 for sampling efforts by location. A single location, the Canard River, and historical population information, are not sufficient to estimate trends in abundance.

N/A = not available; DFO = Fisheries and Oceans Canada; MDNR = Michigan Department of Natural Resources; OMNR = Ontario Ministry of Natural Resources; ROM = Royal Ontario Museum; UTRCA = Upper Thames Region Conservation Authority; UMMZ = University of Michigan Museum of Zoology.

Abundance

Given infrequent detection and relatively low capture numbers of this species, no abundance estimates are available for Pugnose Minnow subpopulations in Canada.

Fluctuations and trends

As a result of lack of detections of Pugnose Minnow from most of the historical collection sites (Barnucz and Drake 2021; Gáspárdy et al. 2025), the distribution of Pugnose Minnow appears to have decreased considerably in Ontario (Table 3). The species rarely occurs in high numbers, making it difficult to detect the magnitude of fluctuations in abundance over time. Extensive sampling using a variety of sampling gears has occurred within the historic range of the species, as detailed below. Given the difficulty in standardizing catch-per-unit-effort among gear types, the relatively few individuals captured and the lack of abundance estimates available for Pugnose Minnow subpopulations in Canada, trends in abundance remain unknown.

Thames River and other historic sites

Sampling in multiple sites within the Thames River has been ongoing since 1980. The Pugnose Minnow was last observed in 1968. DFO conducted regular, general, and targeted sampling from 2002 to 2021. The Pugnose Minnow has not been detected through electrofishing (boat and backpack) or through seine events, and the Pugnose Minnow is presumed extirpated from the Thames River watershed (DFO, unpublished data).

The species has been reportedly captured at other sites in southwestern Ontario, but cannot be verified given the lack of voucher specimens; therefore, these unverified records are excluded from further consideration (DFO 2022).

Lake St. Clair drainage

In Lake St. Clair, the Pugnose Minnow was first recorded in 1935 from Mitchell’s Bay in Lake St. Clair (Royal Ontario Museum [ROM] Catalogue Number 8956); however, only three individuals have been confirmed from Lake St. Clair since this initial observation (two by the ROM in 1979, and a single specimen by the Ontario Ministry of Natural Resources [OMNR] in 2007) (Table 3). Four individuals were reportedly caught along the south shore in 1990 by the MNR; however, no vouchers were taken and proper identification cannot be confirmed (M. Belore, OMNR pers. comm. 2011 in COSEWIC 2012). Species-specific sampling conducted by DFO in 2006 did not recover any individuals. An individual was reportedly captured in 2007 from the south shore of the lake (Bouvier and Mandrak 2013).

The species was documented from four sites in the North Sydenham River system from Bear Creek below Brigden to the North Sydenham River above Wallaceburg in 1979 (Parker and McKee 1980), and caught there again in 2003 (Gáspárdy et al. 2025). The Pugnose Minnow was captured at a single site in the East Sydenham River near Tupperville in 1970 (Parker and McKee 1980), 1997 (Holm and Boehm 1998), and 2010 (Bouvier and Mandrak 2013; Gáspárdy et al. 2025). It was also found in East Otter Creek (a North Sydenham tributary) in 1982, 1996, and 2003 (Mandrak et al. 2006). East Otter Creek was sampled again in 2010 (0 specimens), 2013 (1 specimen) and 2021 (0 specimens) with seines and/or Mamou trawls (Table 3), and the 2013 capture was the last record for this system (Gáspárdy et al. 2025). Additional targeted sampling conducted by DFO in 2019 in the lower Sydenham River, Maxwell Creek, and Little Bear Creek did not collect any Pugnose Minnow (Barnucz and Drake 2021). A total of 46 sites were sampled using a Mamou trawl (total of 183 trawls) in areas where Pugnose Minnow had previously been collected and in adjacent sites with habitat features preferred by the species (Barnucz and Drake 2021).

The Pugnose Minnow has been recorded from additional Lake St. Clair tributaries since 1980: Chenail Ecarté in 1993 and 2010 (COSEWIC 2013), Maxwell Creek and Little Bear Creek in 1982, 1996, and 2003 (Mandrak et al. 2006), 2010 (COSEWIC 2013), and Whitebread Drain in 2003 (Mandrak et al. 2006). DFO has conducted recent surveys throughout the historical range of the Pugnose Minnow. The Chenail Ecarté was sampled from 2010 to 2019 at two to five sites using a bag seine or Mamou trawl, with a single Pugnose Minnow collected in 2010. Maxwell Creek was sampled for Pugnose Minnow in 2010, 2013, and 2019 using bag seines or Mamou trawls, and none were collected (Barnucz and Drake 2021, Gáspárdy et al. 2025). Little Bear Creek was sampled for Pugnose Minnow multiple times between 2005 and 2019 at 18 localities using a variety of methods including Siamese trawl, Mamou trawl (pelagic), and bag seine (DFO 2015, Reid et al. 2016, Barnucz and Drake 2021, Gáspárdy et al. 2025). No Pugnose Minnow have been sampled from Little Bear Creek since 2010 when 11 individuals were collected (Barnucz and Drake 2021; Gáspárdy et al. 2025). The Chenail Ecarté was sampled from 2010 to 2019 at two to five sites using a bag seine or Mamou trawl, with a single Pugnose Minnow collected in 2010. Whitebread Drain was sampled again in 2010 with no Pugnose Minnow recovered from a single seine event (Bouvier and Mandrak 2013). Exploratory sampling was conducted in 2013 and 2021 in the watershed targeting Pugnose Minnow at localities where it had not been previously found but had suitable habitat, including Big Creek (tributary of Little Bear Creek), Indian Creek, and West Otter Creek, but no Pugnose Minnow were detected (Gáspárdy et al. 2025).

Detroit River

The species was captured in 1940 in the Detroit River at Fighting Island (University of Michigan Museum of Zoology [UMMZ] Catalogue Number 130863). Parker and McKee (1980) reported it in the Detroit River based on a 1941 record (ROM 14073), although they did not plot this record on their map. Collections by the ROM (1994 to 1996) and Lapointe (2005) documented the presence of the Pugnose Minnow in the Detroit River.

Canard River

Targeted sampling during 2018 in Canard River at 74 sites with 99 seine events and 123 hauls using Mamou trawl and bag seine (1/8” bag mesh, 1/8” wing mesh, 9.1 m length) resulted in the collection of 294 Pugnose Minnow with 107 collected at a single site (Gáspárdy et al. 2020). Sampling within the Canard River ranged from 10 km upstream of the Essex Terminal railway to the boundary of the confluence with the Detroit River (Gáspárdy et al. 2020). Repeated sampling at multiple sites in the Canard River in 2023 resulted in no Pugnose Minnow collections despite several weeks of targeted sampling, but the lack of detections was hypothesized to be due to reduced effectiveness of sampling gears in the increased water velocity and turbidity during the sampling effort (A. Drake, 2025 personal communication). Targeted sampling in the Canard River in 2024 (39 trawl sites, 40 seine sites) using the same methods and site selection approach as implemented 2018 and 2023 also failed to detect the Pugnose Minnow, with environmental conditions being more similar to the 2018 sampling conditions (A. Drake, 2025 personal communication).

Non-target sampling

Non-target sampling by the DFO’s Asian Carp Early Detection Field Surveillance program has occurred at several of the historical, occupied sites (Table 4). These include the Detroit River (n = 35 sites), the lower Sydenham River (n = 54 sites), and the Canard River (n = 30 sites). However, since 2013, the program has captured Pugnose Minnow only within the Canard River. Many of the gears used for this program are aimed at larger-bodied species and are likely to miss Pugnose Minnow. Moreover, the sample sites tend to be downstream of where the Pugnose Minnow has been detected in the past (Colm pers. comm.). The surveillance program captured Pugnose Minnow in the Canard River in 2013 (n = 3), 2015 (n = 10), 2016 (n = 63), 2017 (n = 1), 2018 (n = 19), 2019 (n = 4), 2020 (n = 1); and 2021 (7 individuals at 3 sites). A sampling of wetland fish communities within the range of the species in 2017 using mini Fyke nets (appropriate for Pugnose Minnow) yielded 20 Pugnose Minnow from 3 sites within the Canard River (Montgomery 2019; Mandrak pers. comm.). An additional Pugnose Minnow was collected in 2017 in a fyke net in the lower Canard River in a survey evaluating fish communities in coastal wetlands near areas of concern (Midwood et al. 2020) (Table 4).

The Pugnose Minnow is now believed to be extant at only one location in Canada, the Canard River. The current extent of occurrences of the Pugnose Minnow is estimated to be 2.65 km². However, as EOO cannot be smaller than IAO, the reported EOO is 12 km². This represents a decrease in the extent of occurrence of 99% of its EOO in Canada detailed in the 2012 status report, which was 1,284 km² (total historical EOO of 4,464 km²). The IAO in the past 10 years is 12 km², an 86% decrease from its IAO of 84 km² in the 2012 report (historical range in Canada of 140 km²).

Continuing decline^{Footnote 1} in number of mature individuals

The status and trends of mature Pugnose Minnow are unknown. However, as the number of subpopulations has declined, it is inferred that the number of mature individuals has also declined.

Evidence for past decline (3 generations or 10 years, whichever is longer) that has either ceased or is continuing (specify)

Size of historical subpopulations are unknown; therefore, the evidence of past decline over the last 10 years is indicated by the decrease in IAO and EOO estimates.

Evidence for projected or suspected future decline (next 3 generations or 10 years, whichever is longer, up to a maximum of 100 years).

Threats to the species are considered High– Low, but there are no quantitative subpopulation data to predict trends in the numbers of mature individuals.

Population fluctuations, including extreme fluctuations

No evidence of extreme fluctuations, although there is no systematic, quantitative sampling of any subpopulation.

Severe fragmentation

There is no evidence (for example, Population Viability Analysis) of fragmentation in the Canadian range of this species.

Rescue effect

The probability of local extirpation may be reduced as suitable habitat may exist throughout the St. Clair and Detroit River systems, potentially allowing movement among Canadian subpopulations and into Canada from American populations. However, as the species has a fragmented distribution and is Critically Imperiled (S1) in the U.S. states adjacent to Canada (Ohio, Michigan, and Pennsylvania), there is likely limited potential for rescue from these populations. In addition, American populations occur in western Lake Erie tributaries located downstream of the Detroit River, where river flows and depths of Lake Erie may act as dispersal barriers that limit immigration of individuals into Canada.

Threats

Historical, long-term, and continuing habitat trends

The federal Recovery Strategy and Action Plan for the Pugnose Minnow identified the overall level of concern for habitat loss and degradation, sediment loading, and nutrient loading as High, and for climate change and exotic species as Medium (DFO 2022) (Table 2). The following threat descriptions have been taken from the Threats Calculator deliberations (Appendix 1).

Current and projected future threats

The Pugnose Minnow is vulnerable to the cumulative effects of various threats, especially habitat alteration, turbidity and sediment loading, nutrient loading, and invasive species (DFO 2022). The nature, scope, and severity of these threats have been described in Appendix 1, following the IUCN-CMP (International Union for the Conservation of Nature – Conservation Measures Partnership) unified threats classification system (see Salafsky et al. 2008 for definitions and Master et al. 2012 for guidelines). The threat assessment process consists of assessing impacts for each of 11 main categories of threats and their subcategories, based on the scope (proportion of population exposed to the threat over the next 10-year period), severity (predicted population decline within the scope during the next 10 years or 3 generations, whichever is longer up to ~100 years), and timing of each threat. The overall threat impact is calculated by taking into account the separate impacts of all threat categories and can be adjusted by the species experts participating in the Threats evaluation.

The overall threat impact for the Pugnose Minnow is considered to be High – Low, corresponding to an anticipated further decline of between 30% and 70% over the next 10 years (or 3 generations, whichever is longer). These values are to be interpreted with caution, as they may be based on subjective information, such as expert opinion, although efforts have been made to corroborate the scores with available studies and quantitative data.

Climate change and severe weather (IUCN 11, overall threat impact medium – low)

Temperature extremes (IUCN 11.3, medium – low, pervasive [71 to 100%], moderate – slight [1 to 30%], high [continuing])

Climate change is expected to have significant effects on aquatic communities of the Great Lakes basin through several mechanisms, including increases in water and air temperatures, lowering of 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). Additionally, warming trends, as a result of climate change, may favour the establishment of potentially harmful exotic species that may currently be limited by cooler water temperatures. It is anticipated that the effects of climate change will be widespread and should be considered a contributing impact to species at risk and all habitats. In an assessment of the projected impacts of climate change on coastal wetland fish assemblages in the Lower Great Lakes, the Pugnose Minnow was considered the most vulnerable of the 99 fish species evaluated (Doka et al. 2006). Brinker et al. (2018) used NatureServe’s climate vulnerability index to consider how the distribution and abundance of species will be impacted. They considered the Pugnose Minnow moderately vulnerable based on an assessment of climate change risk for species at risk in Ontario based on thermal preferences for different life stages as well as species’ distributions.

Storms and flooding (IUCN 11.4, low, pervasive [71 to 100%], slight [1 to 10%], high [continuing])

The intensity and frequency of storms and associated flooding is increasing. However, there are no data available specific to the behavioural or population responses of the Pugnose Minnow to intense storms.

9.0 Pollution

Domestic and urban waste water (9.1, cd, medium – low, large [31 to 70%], moderate – slight 30%, high [continuing])

Nutrient loading can occur through wastewater management, septic systems, stormwater and surface water runoff, and municipal sewage. Improper nutrient management can cause loading of nearby waterbodies. Elevated nutrient levels can cause increased aquatic plant growth, change water temperatures, and slowly change preferred flows and substrates. Dissolved oxygen levels can also be negatively impacted. Nutrient loading can impact reproduction, development, feeding, and cover in slow moving areas of streams.

Contaminants and toxic substances through the over application or misuse of herbicides and pesticides, and release of domestic and urban pollution into Pugnose Minnow habitat can negatively impact this species. Moreover, there are many personal care products and pharmaceuticals (PCPPs) that enter surface waters in southern Ontario through ground water and wastewater treatment plants (for example, Arlos et al. 2015), with uncertain impact on the Pugnose Minnow.

The introduction of toxic compounds can change water chemistry, which affects habitat availability or use, and can cause increased aquatic plant growth affecting spawning and recruitment success. Contaminants and toxic substances can impact reproduction, development, feeding, and cover in slow moving areas of streams. Improper sediment and erosion control or mitigation measures along roadsides and urban properties can cause increased turbidity levels, changing preferred substrates and their oxygen levels, potentially reducing feeding success or prey availability, impacting the growth of aquatic vegetation and possibly excluding fishes from habitat due to physiological impacts of sediment in the water. The direct impacts of water quality effects on this species have not been documented.

Agricultural and forestry effluents (9.3, cd, medium – low, moderate – slight [1 to 30], high [continuing])

Nutrient loading can occur through the over-application of fertilizer and improper nutrient management (for example, organic debris management), and animal waste. Elevated nutrient levels can cause increased aquatic plant growth, slowly change preferred flows and substrates, and alter prey supplies. Dissolved oxygen levels can also be negatively impacted by decomposition of excess production. Nutrient loading can impact reproduction, development, growth, feeding, and cover in slow-moving areas of streams. Habitat alteration can occur through uncontrolled livestock access to waterbodies (trampling by livestock scored here), grazing by livestock, and ploughing to water’s edge (Threat 2.1) can result in damage to shorelines, banks, and watercourse bottoms that can cause increased erosion and sedimentation, which affects turbidity and substrate oxygenation. Pesticides used for agriculture (herbicides, insecticides, antibiotics and fungicides) can be released into water bodies, with diverse impacts, none of which are yet documented for the Pugnose Minnow.

Habitat alteration can also occur through the mechanical and chemical removal of aquatic and riparian vegetation (not usually due to livestock) that can lead to erosion and increased turbidity which affects preferred substrates and oxygenation of substrates. Water temperatures can also be negatively affected by removal of riparian vegetation and water velocities can be increased during high water events. Habitat alteration can impact reproduction, development, growth, feeding, and cover in slow moving areas of streams.

Turbidity and sediment loading occur through the altering of flow regimes causing erosion and changing sediment transport (for example, field tillage and tiling of agricultural drains). Sediment loading can also occur through work in or around water with improper sediment and erosion control (for example, overland runoff from ploughed fields).

7.0 Natural system modifications

Dams and water management/use (7.2, negligible, pervasive [70 to 100%], negligible [<1%], high [continuing])

Three types of barriers to fish movement are found in southwestern Ontario: 1) dams and weirs; 2) pumped watercourses; and, 3) diked wetlands. Several watercourses that drain into Lake St. Clair have pumps to ensure proper drainage of tributaries and drains. The extent to which these pumps restrict access for fishes in these watercourses remains unclear. Site-specific conditions may afford protection for some species from competitors, exotic species and predators; however, the barriers may prevent access to suitable habitat and lead to fragmentation of subpopulations. Water withdrawal within the watersheds may exacerbate low flows, contributing to warmer temperatures, smaller habitat availability, and concentration of nutrients. Habitat alteration through water extraction or changes in the timing, duration and frequency of flow can affect surface water flow and levels, and groundwater inputs into streams and rivers that affect habitat availability, oxygen levels, and prey abundance. Altered flow patterns can affect sediment deposition (for example, changing preferred substrates), oxygenation of substrates, and prey abundance.

Other ecosystem modifications (7.3, medium – low, pervasive [70 to 100%], negligible [<1%], high [continuing])

Natural coastal processes that occur near the shorelines, along lakes and large rivers, include sediment erosion and deposition that provide and maintain habitat for fishes. Much of the shoreline habitat along Lake St. Clair and the Detroit River has been artificially hardened (for example, riprap, groynes) for industry and recreation. Waterways have been dredged for shipping, flood control, or cleaning of agricultural drains. Increases in the numbers of drains for agricultural land have occurred. In addition to direct changes, these activities contribute to turbidity. Large wood (snags) has often been cleared from surface waters, potentially removing security cover for the Pugnose Minnow. Shoreline modifications that remove tree cover result in less shading, greater short-wave and long-wave radiation leading to heating of water, and greater rates of photosynthesis, all of which have the potential to affect the Pugnose Minnow.

Habitat alteration can occur through a variety of mechanisms. Dredging, grading, excavation, placement of material or structures in water (for example, groynes, piers, infilling, partial infills, jetties, and shoreline hardening) can cause changes in bathymetry and shoreline morphology and can remove preferred substrates, change water depths, cause erosion and alter turbidity levels, change flow patterns, and potentially affect nutrient levels and water temperatures. Dredging can also result in the removal of the aquatic vegetation seed bank. Materials placed in the water reduce available habitat and the placing of fill can cover preferred substrates. The hardening of shoreline can reduce organic inputs into the water and can also alter water temperatures which may affect prey availability for the Pugnose Minnow.

Number of threat locations

This wildlife species has only been collected in one watershed (Canard River) in the last 12 years. Given that the threats apply to the entire river, it qualifies as one location.

Protection, status, and recovery activities

Legal protection and status

The Pugnose Minnow was listed as a species of Special Concern in 2003 under Schedule 1 of the Species at Risk Act (SARA) and as Threatened in 2019. Additional protection is given through Canada’s Fisheries Act. A Recovery Strategy / Action Plan has been developed for the Pugnose Minnow through the Species at Risk Program (Fisheries and Oceans Canada 2022). It is also addressed in the Sydenham River Action Plan (DFO 2013); Thames River Ecosystem Recovery Strategy (TRRT 2005); and Essex-Erie Region Fishes at Risk Recovery Strategy (EERT 2008). Additionally, Endangered and Threatened species that occur within the Canadian range of the Pugnose Minnow that have single-species recovery strategies and may be relevant to its recovery include: the Pugnose Shiner (Fisheries and Oceans Canada 2024), Eastern Sand Darter (Ammocrypta pellucida) (DFO 2012b), Round Hickorynut (Obovaria subrotunda), Kidneyshell (Ptychobranchus fasciolaris) (DFO 2013), Northern Riffleshell (Epioblasma rangiana), Snuffbox (Epioblasma triquetra), Round Pigtoe (Pleurobema sintoxia), Salamander Mussel (Simpsonaias ambigua), and Rayed Bean (Paetulunio fabalis) in Canada (DFO 2017).

In Ontario, the Pugnose Minnow was listed as Threatened under both the province of Ontario’s Endangered Species Act (2007) in 2013 and assessed as Threatened by the Committee on the Status of Species at Risk in Ontario (COSSARO) in 2012. Destruction or alteration of riparian areas and wetlands are regulated and protected under the Conservation Authorities Act and under the Provincial Planning Act.

Non-legal status and ranks

NatureServe Explorer (2017) lists the Pugnose Minnow as Globally Secure (G5) and Imperiled Nationally (N2) within Canada and Imperiled Provincially (S2) within Ontario. The Pugnose Minnow is listed as Critically Imperiled (S1) in Michigan, Ohio, and Pennsylvania in the United States. The Pugnose Minnow is listed as Vulnerable in Wisconsin, Georgia, Oklahoma, Arkansas, Indiana, Illinois, and Iowa; Apparently Secure in Kentucky, Missouri, Texas, Minnesota; and Secure in Tennessee, Alabama, Mississippi, and Louisiana. The Pugnose Minnow is presumed extirpated in West Virginia.

Land tenure and ownership

In Canada, the habitat of the Pugnose Minnow and all fishes is protected under Canada’s Fisheries Act that prohibits harmful alteration, disruption or destruction of fish habitat. Most of the lands adjacent to known sites of the Pugnose Minnow are private. In Ontario, few, if any, parks and conservation areas have been established specifically to preserve aquatic biodiversity. However, some actually do protect aquatic biodiversity as a result of their location and management practices (Mandrak and Brodribb 2005). Komoka Provincial Park may serve to protect the Pugnose Minnow, if still present in the Thames River watershed.

Recovery activities

The Pugnose Minnow Recovery Strategy and Action Plan (DFO 2022) has determined that, based on the criteria for recovery feasibility, recovery of the Pugnose Minnow is believed to be biologically and technically feasible. Specific subpopulation and distribution objectives were identified and are in various stages of implementation (Fisheries and Oceans 2022). See the plan for details.

Information sources

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Collections examined

No collections were examined for the preparation of this report.

Authorities contacted

• COSEWIC Secretariat
• De Forest, L. Species Conservation Specialist, Parks Canada
• Colm, Julia. Species at Risk Science Advisor, Great Lakes Laboratory for Fisheries and Aquatic Sciences, Fisheries and Oceans Canada
• Drake, Andrew. Research Scientist, Great Lakes Laboratory for Fisheries and Aquatic Sciences, Fisheries and Oceans Canada
• Holm, Erling. Assistant Curator Ichthyology (retired), Royal Ontario Museum
• Ilves, Katriina. Research Scientist, Canadian Museum of Nature
• Jones, Colin. Provincial arthropod zoologist, Ontario Natural Heritage Information Centre, Ontario Ministry of Natural Resources and Forestry
• Mandrak, Nicholas, Professor, Department of Biological Sciences, University of Toronto Scarborough
• Pickett, Karolyne. Species at Risk Biologist, Canadian Wildlife Service
• Pitcher, Trevor. Professor, Great Lakes Institute for Environmental Research, Department of Integrative Biology, University of Windsor
• Reid, Scott. Research Scientist, Aquatic Research and Monitoring Section, Ministry of Natural Resources and Forestry

Acknowledgements

Funding for the preparation of this report was provided by Environment and Climate Change Canada. The reports writer would like to thank Andrew Drake, Fisheries and Oceans Canada, and NHIC for data provided. The report writers would also like to thank Scott Gibson and Nick Mandrak, authors of the 2012 Status report.

Biographical summary of report writers

Terin Robinson is an Aquatic Ecologist at RiverStone Environmental Solutions Inc. She has a BSc (Guelph) in Ecology where she completed an honours research project on the behavioural ecology of Mangrove Killifish. Her master’s (Trent) research focused on mate choice in Brook Trout using microsatellites and behavioural observation, and her doctoral work (Waterloo) focused on the immunogenetics of Arctic charr. Her future research interests focus on the ecology, evolution, and conservation of freshwater fishes.

Bev Wicks is a Senior Ecologist and Principal at RiverStone Environmental Solutions Inc. Her MSc (Guelph) and PhD (UBC) were related to factors influencing sex ratios in Lamprey and physiological responses relating to questions around toxicity and ammonia exposure in salmonids. Bev has authored multiple journal articles and reports on fish and fish habitat and has worked at and continues to be interested in the intersection between development, policy, and the protection of fishes and their habitat.

Al Shaw is a Senior Ecologist and Principal at RiverStone Environmental Solutions Inc. He holds a BSc (Guelph) and an MSc (UBC), which focused on invertebrate and fisheries ecology. Al has authored numerous reports and serves on the advisory committee for fisheries management zones. Al continues to be interested in issues of fish conservation.

Appendix 1 – IUCN-CMP threats calculator spreadsheet

Threats assessment worksheet

Species or Ecosystem scientific name: Pugnose Minnow, Opsopoeodus emiliae

Assessor(s): Dwayne Lepitzki (Facilitator), John Richardson (SSC Co-chair), Terin Robinson (Report writer), Bev Wicks (Report writer), Jennifer Diment, Trevor Pitcher, Olivier Morissette, Karl Lamothe, Julia Colm, Andrew Drake, Karine Robert (Secretariat), Madison Shaw (Secretariat), Brent Patterson, Scott Reid.

References: Draft calculator provided by report writer(s) based on draft COSEWIC status report and 2022 DFO RS and AP (from Edwards and Staton 2009; Bouvier and Mandrak 2013); teleconference from May 22, 2024.

Assigned overall threat impact: BD = High– Low

Overall threat comments: Generation time 1 to 2 years, so timeframe for severity and timing is 10 years into the future. The species may currently be confined to Canard River, a tributary of the Detroit River (last collected in 2018, not captured in 2023). The species has been extirpated in the Thames and Sydenham rivers. The threats assessment is confined to Canard River where there has been intensive, targeted sampling in the past several years. Given how rarely this species has been collected in the past two decades, the population size is unknown, and there are insufficient collections to address trends in numbers.