Recovery Strategy for the Eastern Sand Darter
1.1 Species Information
Scientific Name: Ammocrypta pellucida (Agassiz 1863) Common Name: Eastern sand darter, dard de sable Current COSEWIC Status & Year of Designation: Threatened 2000 Canadian Occurrence: Ontario, Quebec Reason for Designation: Loss of habitat and deteriorating water quality since the 1950s due to siltation, impoundments and chemical pollutants has resulted in reduced distribution and population declines. In Canada, this species has a limited disjunct distribution; populations are isolated and there is little chance of re-colonization if local extinctions occur. Status History: Designated Threatened in April 1994. Status re-examined and confirmed in November 2000. Last assessment based on an existing status report with an addendum.
Classification: The current classification of the eastern sand darter is (from the Integrated Taxonomic Information System on-line database, http://www.itis.usda.gov. Retrieved March 07, 2005):
Recent molecular analyses support a monophyletic genus Ammocrypta (Song et al. 1998, Near et al. 2000, Sloss et al. 2004). Ammocrypta clara (western sand darter) and A. vivax (scaly sand darter) have previously been considered subspecies and/or synonyms of A. pellucida (Grandmaison et al. 2004); both are now considered valid species. Records of A. pellucida in the Mississippi River drainage north of the Ohio River confluence represent A. clara while records from the southern reaches represent A. clara or A. vivax (Williams 1975). Ammocrypta pellucida and A. clara have overlapping distributions in Indiana and Illinois within the Wabash River drainage, and in Kentucky within the Cumberland and Green river drainages.
1.2 Species Description
The eastern sand darter is a small fish with translucent flesh and an elongate body, almost round in cross-section (Scott 1955) (Figure 1). Adults range in length from 46-71 mm TL (Trautman 1981), averaging 64 mm TL (Scott and Crossman 1973). Adults exhibit a faint yellowish or greenish colouration on the dorsal surface of the head and body, a narrow metallic gold to olive-gold band passing subcutaneously along a line of lateral green rounded blotches, and a white or silvery hue on the ventral surface (Trautman 1981). Young fish are more silvery with little or no yellow (Scott and Crossman 1973, Trautman 1981). Males in breeding condition are flushed with a yellowish colouration and develop tubercles on their pelvic fins. A row of 12 -16 dark greenish blotches are located along the dorsum, which differentiate into rows of paired spots along the base of the dorsal fins, one spot on either side of the fin (Trautman 1981). Nine to 14 (10-14 Scott and Crossman 1973; 9-14 Trautman 1981; 10-14 Holm and Mandrak 1996) spots also occur along the lateral line (Trautman 1981). Webbing of fins is transparent; although some individuals sport a yellowish tinge (Trautman 1981). Dorsal fins are separate; the first dorsal fin is spiny (8-11 weak spines), and the second dorsal has soft rays (9-12 rays) (Scott and Crossman 1973). Males have black pigment on the pelvic fin (Page and Burr 1991). Scales are absent from its ventral side 1-3 scale rows immediately beneath the lateral line (Trautman 1981). à
Figure 1. The eastern sand darter (Ammocrypta pellucida).
1.3 Populations and Distribution
GlobalRange (Figure 2): The eastern sand darter inhabits the Ohio River and Great Lakes drainage and is also found in the Lake Champlain and St. Lawrence River drainages (Figure 2) (Scott and Crossman 1973) which forms part of a disjunct element of the distribution. It occurs in the Canadian provinces of Ontario and Quebec and nine American states: Illinois, Indiana, Kentucky, Michigan, New York, Pennsylvania, Ohio, Vermont and West Virginia.
Figure 2. Eastern sand darter distribution in North America
Ontario – In Ontario, it has been collected from shallow habitats in lakes Erie and St. Clair, and from the Grand, Sydenham and Thames rivers (Holm and Mandrak 1996) (Figure 3). Populations are presumed to be extirpated from the Ausable River, Catfish Creek, Big Creek and Big Otter Creek (ARRT 2005).
Sydenham River: Along the East Branch between the Shetland Conservation Area and Dawn Mills, with a disjunct population further upstream between Strathroy and Alvinston (Dextrase et al. 2003).
Ausable River: There is a single record of eastern sand darter occurring in the river near Ailsa Craig from a 1928 survey. Subsequent searches at this site failed to recapture the species.
Catfish Creek: The eastern sand darter was collected from Catfish Creek in 1922 and 1941. It has not been collected in more recent surveys.
Big Creek: The eastern sand darter was collected from Big Creek in 1923 and 1955. It has not been collected in more recent surveys.
Big Otter Creek: The eastern sand darter was collected from Big Otter Creek in 1923 and 1955. It has not been collected in more recent surveys.
Grand River: All sandy areas in the lower main stem from Brantford to Cayuga.
Lake Erie: Pelee Island (no recent collections), Rondeau Bay and Inner Long Point Bay.
Lake St. Clair: Eastern sand darter has been collected from two areas of Lake St. Clair over the past 25 years. The south shore between the outlet of Pike Creek and the Thames River, and Mitchell’s Bay.
Thames River: This species has been found in suitable habitat in the lower Thames River watershed, mainly between Komoka and Kent Bridge. ROM surveys from 1981-1991, and DFO surveys from 2003-2005, found this species extant at most historical sites.
Figure 3. Ontario distribution of the eastern sand darter.
Quebec – InQuebec, eastern sand darter is found mainly in the St. Lawrence River and its tributaries, between Lake of Two Mountains and Leclercville, downstream from Lake St. Pierre (Figure 4) (Gaudreau 2005). In the St. Lawrence River, a few specimens have recently been collected in Lake St. Pierre and in its archipelago, as well as in a reach between Montreal and Sorel (N. La Violette, unpublished data, Gaudreau 2005). The species was also identified in a few tributaries from six areas of the province: Centre du Québec, Lanaudière, Laval, Mauricie, Montérégie and Montreal.
From the time eastern sand darter was first officially caught in 1941, the species has been identified in 11 rivers in Quebec (Table 1). Prior to 1985, its presence was confirmed in nine streams in the areas of Centre du Québec, Lanaudière, Laval, Mauricie, Montérégie and Montreal. Since 1985, the presence of eastern sand darter has been re-confirmed only in the Richelieu and Assomption rivers, and specimens have recently been collected in the Ouareau River in 2002 and 2003 (Holm and Mandrak 2000, Gaudreau 2005)
The eastern sand darter was caught in Lake of Two Mountains in 1941 and 1946. This area was sampled again in 1964, 1977 and 1990, but no specimens were caught (Holm and Mandrak 1996, Gaudreau 2005).
The species was observed in the Châteauguay River in 1941 (Vladykov 1942) and more than 180 specimens were caught in 1943 (Cuerrier et al. 1946). A few catches were made in 1975 and 1976 (Mongeau et al. 1979; cited in Gaudreau 2005). However, eastern sand darter was not detected during the 1993 sampling campaigns (La Violette and Richard 1996). In 2006, a specimen was caught in the Trout River (a tributary of the Châteauguay River) (S. Garceau, pers. comm.).
Sampling was conducted on the Yamaska River in 1995 and 2003 and no eastern sand darter were captured, even though they had been observed in this river in 1967 (Mongeau 1979; cited in Gaudreau 2005, La Violette 1999).
Cuerrier (1946) mentioned that eastern sand darter was abundant in the St. François River in 1944. However, no specimens were caught in this river during surveys conducted in 1965, 1974, 1991, 2002 and 2003 (Mongeau and Legendre 1976, Richard 1996, Gaudreau 2005).
In Quebec, the species has never been the target of a specific study, other than a rare fish species inventory conducted in the southern part of the Assomption River drainage basin in the Lanaudière area in 2002. A total of nine eastern sand darter were collected during this inventory in the Assomption and Ouareau rivers (CARA 2002).
The little data available concerning eastern sand darter populations does not provide sufficient proof to definitely confirm its disappearance from certain streams in Quebec. Many streams where it had been previously caught have not been sampled for approximately fifteen years. Furthermore, it’s a difficult species to track visually and catch because of its small size, its benthic lifestyle, its burrowing behaviour and its translucency (Gaudreau 2005).
Figure 4. Eastern sand darter observation sites in Quebec.
Table 1. Eastern sand darter reported occurrence in Quebec.
( √ = Occurrence of the species; x = the species was not caught during sampling)
|St. Lawrence River|
|1 St. François Lake||x||x||*|
|St. Louis Lake||x||*|
|Lake St. Pierre archipelago||√||√||x||√||*, 11, 24, 39|
|Lake St. Pierre||x||x||√||*, 24, 39|
|1 Gentilly-Batiscan reach||x||*|
|1 Grondines-Donnacona reach||x||*|
|Lake of Two Mountains||√||x||x||x||24, 28|
|Châteauguay River||√||√||x||√||11, 24, 37, 46, 78|
|Yamaska River||√||x||x||24, 38, 47|
|St. François River||√||x||x||x||x||11, 24, 45|
|Yamachiche River||√||√||24, 28|
|Bécancour River||√||24, 28|
|Gentilly River||√||√||24, 28|
|Orignaux River||√||24, 28|
|Du Chêne River||√||24, 28|
1 Eastern sand darter has never been caught in these sections of the St. Lawrence River in spite of experimental fisheries carried out by the Réseau de suivi ichtyologique (RSI).
*: La Violette, N., unpublished data.
**: Garceau, S., personal communication
Percent of Global Range in Canada: NatureServe (2005) estimates just over 100 extant occurrences of eastern sand darter in North America. Grandmaison et al. (2004) identified approximately 75 streams where eastern sand darter is extant. As there are approximately 12 extant occurrences in Canada, around 10 to 16% of the eastern sand darter’s global range is found in Canada.
Distribution Trend: Habitat loss and poor water quality have resulted in a reduced distribution. In Canada, eastern sand darter has declined or become extirpated from 12 of 21 locations. Over the past 50 years, 45% of population occurrences in Ontario have been lost (ARRT 2005). Several new sites have been found since the 1970s; however, the net result is a reduction in distribution (Holm and Mandrak 1996). In Quebec, inventories conducted since 1990 at seven of the 12 ″historical″ sites where the species’ presence has been documented (Table 1), have confirmed its presence in four of the seven sites (57%). These inventories have led to the addition of four new observation sites. However, five sites where eastern sand darter was documented during the 1970s and 1980s have not been sampled since that time. The eastern sand darter seems to have been extirpated from Lake of Two Mountains as well as the Yamaska and St-François rivers. Its range in Quebec, therefore, seems to have been reduced.
Population Size and Status:
Global Population Size and Status:There is little information available concerning the abundance of the eastern sand darter over its entire global range. The little data that are available suggest that eastern sand darter populations are declining throughout their entire range. The short-term rate of decline would be between 10% and 30%, whereas long-term decline would fluctuate between 50% and 75% ( Holm and Mandrak 2000). NatureServe (2006) estimates the eastern sand darter global abundance to be between2,500 and 100,000 individuals.
The eastern sand darter has experienced population declines throughout its global range (Page and Burr 1991, Holm and Mandrak 1996). It has been considered globally rare (G3) since 1996 (NatureServe 2005) and was designated as Vulnerable by The World Conservation Union (IUCN) in 1996 (Gimenez 1996).
The eastern sand darter is not listed federally in the United States. The American Fisheries Society has designated this species as Threatened in the United States since 1989 (Williams et al. 1989). It is listed as Endangered in Pennsylvania (State of Pennsylvania 2005) and Threatened in Illinois (Illinois Department of Natural Resources 2003), New York (New York State Department of Environmental Conservation 2003), Michigan (Michigan Department of Natural Resources undated) and Vermont (M. Ferguson, Vermont Agency of Natural Resources, pers. comm.). It is considered a Species of Concern in Ohio (Ohio Department of Natural Resources 2002). It was previously listed as Special Concern in Indiana; however, it was downlisted after a statewide survey in 2004 determined it to be well distributed (B. Fisher, Indiana Department of Natural Resources, pers. comm.).
Canadian Population Size and Status: In Canada, eastern sand darter population sizes are unknown, but numbers are nevertheless in decline since 1950 according to estimates. Holm and Mandrak (2000) estimated that the rate of decline would have reached 50% between 1955 and 1970. They also estimated that the species’ extent of occurrence (based on the length in km of the rivers occupied by the species) was less than 20,000 km2.
The eastern sand darter is listed on Schedule 1 of the Canadian Species at Risk Act. It is ranked N3 in Canada and COSEWIC designated it as Threatened. It is designated Threatened in Ontario by the OMNR and has an S-rank of S2 in both Ontario and Quebec. It is also in the process of being designated as Threatened in Quebec by the Ministere des Ressources naturelles et de la Faune (D. Banville, comm. pers.). See Table 2 for national and sub-national ranks.
Percent of Global Abundance in Canada:No global or Canadian abundance estimates have been undertaken.
Population Trend: The eastern sand darter was presumed common and widespread in the early 1900s (Holm and Mandrak 1996). However, it is estimated to have disappeared from half of its historical locations and its abundance reduced in remaining populations.
Stable populations are presumed to exist in the Grand and Thames rivers in Ontario (Holm and Mandrak 1996). It is not clear whether populations are stable in Lake Erie as standard fish surveys in suitable habitat areas along the Lake Erie shoreline have not been completed and the species may be data deficient. Eastern sand darter are extant at Rondeau Bay and Long Point but may be heavily impacted by the round goby (Neogobius melanostomus) (French and Jude 2001, Baker 2005) , and there have been no recent collections at Pelee Island.
In Quebec, presumed stable populations are present in Lake St. Pierre in the St. Lawrence River and from ten other tributaries of the St. Lawrence. It is thought to be present in the Assomption River. Populations are believed to have declined or become extirpated from the Châteauguay, Gentilly, Yamaska and St. François rivers (Gaudreau 2005). Trends at remaining locations are unknown.
Table 2. Rank and status given to the eastern sand darter (from Gaudreau 2005).
|Location||Status rankings ||Organization responsible for providing the status or rank|
|World Conservation Union (IUCN); NatureServe|
|United States||Threatened N3||American Fisheries Society (AFS); NatureServe|
|Canada||Threatened N3||Committee on the Status of Endangered Wildlife in Canada (COSEWIC); NatureServe|
In process: Threatened
|Ministère des Ressources naturelles et de la Faune (MRNF); Centre de données sur le patrimoine naturel du Québec (CDPNQ)|
1.4 Needs of the Eastern Sand Darter
1.4.1 Habitat and Biological Needs
Habitat Description: The eastern sand darter inhabitsstreams, rivers and sandy shoals in lakes, and is typically strongly associated with fine sandy substrates (greater than 90% sand) in areas of shallow water (<0.5 m deep) with relatively slow currents (<0.2 m/s) (Daniels 1993, Facey 1995, Facey and O’Brien 2003). Abundance is greatest on the depositional side of bends along small- to medium-sized rivers with a gentle current and minimal fine sediment deposition (Trautman 1981, Facey 1995). Few fishes of temperate streams are as strongly associated with a specific habitat type as this species. Daniels (1993) found the nearest neighbouring fish was overwhelmingly (93%) another eastern sand darter, showing also that individuals aggregate in areas of suitable habitat. Eastern sand darters are also found near sandbars, in shallow pools (Welsh and Perry 1997), in the sandy raceways of streams and rivers (Kuehne and Barbour 1983, Page 1983), or in gravelly riffles.
Lentic populations of eastern sand darter in Ontario (i.e. lakes Erie and St. Clair) and Quebec, are typically associated with nearshore habitats such as wave-protected sandy beaches, sandy shores and shallow bays (van Meter and Trautman 1970, Thomas and Haas 2004, Gaudreau 2005).
The eastern sand darter is typically found in shallow habitats. Facey (1995) did not find eastern sand darters in deep habitats characterized by high velocities and coarser sand. However, lack of capture from deep habitats may be, in part, an artifact of sampling method and accessibility rather than habitat preference (i.e. choice of sampling stations is typically dictated by accessibility) (Daniels 1993, Facey 1995, Welsh and Perry 1997, O’Brien and Facey 2003). In Lake Erie, Scott and Crossman (1973) reported a trawl-caught individual at a depth of 14.6 m.
Currently Occupied Habitat:
SydenhamRiver: Relatively continuous distribution along the eastern branch between the Shetland Conservation Area and Dawn Mills, with a disjunct population further upstream between Strathroy and Alvinston.
Grand River: Lower Grand River: Brantford downstream to Cayuga.
Lake Erie: Rondeau Bay and Inner Long Point Bay (Surveys in areas of suitable habitat along the shore of Lake Erie have not been completed; therefore, species may be data deficient).
Lake St. Clair: The south shore between the outlet of Pike Creek and the Thames River, and Mitchell’s Bay.
ThamesRiver: The lower Thames River between Komoka and Kent Bridge.
St. Lawrence River: from Montréal to Lake St. Pierre
St. Lawrence Rivertributaries:
Lake of Two Mountains: Anse à l’Orme and Sainte-Marthe-sur-le Lac.
ChâteaugayRiver: Near Mercier and between Châteauguay and Athelstan.
AssomptionRiver: In the vicinity of L’Assomption and Joliette.
OuareauRiver: Near Crabetree.
RichelieuRiver: Between McMasterville and the mouth of the Saint-Marc River; in the Chambly Basin; and in Missisquoi Bay.
YamachicheRiver: Near the mouth.
Gentilly River: In the vicinity of Bécancour.
Aux Orignaux River
Du Chêne River
Historically Occupied Habitat: This is defined as “all areas of current occupation as well as all areas of historical occurrence”. Re-introductions should not be considered until it can be demonstrated that habitat at historical sites is suitable.
Lake Huron Drainage: Ausable River
Lake St. Clair Drainage: Lake St. Clair, Sydenham River, Thames River
Lake Erie Drainage: Lake Erie (including Pelee Island), Catfish Creek, Big Creek, Big Otter Creek, Grand River
St. Lawrence River: From Montréal to Lake St. Pierre
St. Lawrence River Tributaries: Châteauguay River, Trout River, Assomption River, Ouareau River, Richelieu River, Yamaska River, St. François River, Yamachiche River, Bécancour River, Gentilly River, Orignaux River, Du Chêne River, Lake of Two Mountains
Habitat Trends in Ontario: In most eastern sand darter watersheds, increased siltation as a result of intensive agricultural practices is believed to have degraded its preferred sand habitats (Holm and Mandrak 1996). In the Sydenham and Ausable rivers, high turbidity and nutrient levels have likely contributed to habitat degradation. Habitats along the Sydenham River have been affected by siltation (Holm and Mandrak 1996) and relatively few silt-free patches remain (Dextrase et al. 2003). Heavily impacted by agricultural and urban development, the Thames River is adversely affected by high nutrient loads (phosphorous and nitrogen) and turbidity levels (TRRT 2004). In Big Otter Creek and Catfish Creek, where the species is extirpated, agricultural nutrient and sediment loading is considered a severe obstacle to recovery.
In the Grand River watershed, efforts to improve water quality have been largely successful (Plummer et al. 2005). However, the human population is expected to increase by 37% over the next 20 years (Krause et al. 2001) and stresses on the aquatic ecosystem resulting from land use changes, water utilization, sewage disposal and recreational activities are expected to increase. Along the lower Grand River, the Caledonia dam is a permanent barrier to two-way movement between eastern sand darter populations in the area of the Oxbow and those between Caledonia and Cayuga. Higher levels of sedimentation and turbidity downstream of Caledonia may also restrict the range of eastern sand darter in this stretch of the river.
Over the period of 1955 to 1980, Lake Erie was affected by extensive oxygen depletion and changes in the benthos that resulted from its eutrophic state (Koonce et al. 1996). While water quality has improved greatly, the nearshore of Lake Erie and of Lake St. Clair has been extensively modified by shoreline hardening, groynes, jetties and breakwaters, thereby, reducing aquatic habitat diversity and altering nearshore sediment transport (Koonce et al. 1996). By disrupting natural erosion processes and nearshore sediment transport, nearshore habitats such as wave-protected sandy beaches, sandy shores and shallow bays are likely to be negatively affected.
Habitat Trends in Quebec: In Quebec, eastern sand darter inhabited or currently inhabits four of the most polluted rivers of Quebec, i.e. the Assomption, Richelieu, Yamaska and St. François rivers. The species has likely been extirpated from the St. François and Yamaska rivers. It’s status in the Assomption and Richelieu rivers is not known with certainty. These rivers flow through areas consisting primarily of agricultural and urban lands. Consequently, water quality is very poor, with high turbidity, as well as high concentrations of nutrients, pesticides, suspended solids and organic matter. Moreover, these waters drain directly into Lake St. Pierre, an area where eastern sand darter is also present. It is estimated that these four rivers inject nearly 800,000 tons of suspended solids into Lake St. Pierre annually as a result of agricultural land erosion, They also contain massive quantities of nitrogen and phosphorus, resulting from excessive spreading of solid and liquid manures (MDDEP 2007). The nitrogenous products (nitrates) and the phosphates cause imbalances in the rivers, which result in their eutrophication. The excessive development of aquatic plants, algae or periphyton, results in a decrease in the quantity of dissolved oxygen in the water. This poses a serious threat to benthic species such as the eastern sand darter (FAPAQ 2002).
In Lake St. Pierre, the some 4,000 high-tonnage ships transiting there, increases the intensity of the waves which move several tons of sediment. The passage of high-tonnage ships also provokes bank erosion and accelerates silting (Gaudreau 2005). The impact of recreational boating on the smallest rivers, for example the Richelieu River, is also considerable.
The massive deforestation on each side of the St. Lawrence River and of the majority of the rivers where eastern sand darter is found, to increase cultivable areas, increases runoff, sedimentation and nutrient enrichment in the brooks and rivers, which will affect the habitat of eastern sand darter (FAPAQ 2002, Vachon 2003).
In Quebec, certain rivers where populations of eastern sand darter were historically and are currently found, are harnessed, in particular the Ouareau, Richelieu and Yamaska rivers. The construction of dams modifies the flow of the rivers and supports eastern sand darter habitat sedimentation and destruction (Holm and Mandrak 1996, Grandmaison et al. 2004, Gaudreau 2005, NatureServe 2006).
Federal: Once defined, the critical habitat of the eastern sand darter will receive protection under the Species at Risk Act, as it is a Threatened species listed under Schedule 1 of the Act. The eastern sand darter receives general protection under the habitat provisions of thefederal Fisheries Act. Under the Fisheries Act, its habitat is protected from disruption or destruction unless authorized by the Minister of Fisheries and Oceans or his/her delegate.
Ontario: Planning authorities “must be consistent with” the provincial Policy Statement under Section 3 of Ontario’s Planning Act that prohibits development and site alteration in the habitat of Endangered and Threatened species. The Ontario Lakes and Rivers Improvement Act prohibits the impoundment or diversion of a watercourse if siltation will result and the voluntary Land Stewardship II program of the Ontario Ministry of Agriculture, Food and Rural Affairs is designed to reduce erosion on agricultural lands. Stream-side development in Ontario is managed through floodplain regulations enforced by local conservation authorities. A majority of the land adjacent to the rivers inhabited by eastern sand darter is privately owned; however, the river-bottom is generally owned by the Crown.
Quebec: Two provincial acts protect the habitat of all fishes, including the eastern sand darter, in Quebec: 1) the Conservation and Development of Wildlife Act; and, 2) the Environment Quality Act.
1.4.2 Ecological Role
The eastern sand darter is one of the rare species that exploits sandy habitats and related resources. It is also the only Ammocrypta type representative in Canada and, consequently, an integral part of Canada’s wildlife heritage. In addition to contributing to the biodiversity of aquatic ecosystems, this species is an indicator of unpolluted streams (Gaudreau 2005).
1.4.3 Limiting Factors
The eastern sand darter is not very flexible in terms of habitat needs (i.e. it is dependent on silt-free, soft, fine sand). It is vulnerable to any factor likely to affect its habitat (Holm and Mandrak 2000, Grandmaison et al. 2004, Gaudreau 2005, NatureServe 2006). The silting of sandy bottoms and sedimentation reduce the oxygen concentrations in the substrate and therefore affects the species’ burrowing and reproductive behaviour. Silting can also reduce the number of spawning sites available and egg survival; well-oxygenated clean sand is required for the survival of eggs, in which they are deposited and incubated. Siltation can also cause significant changes in the community structures of aquatic invertebrates on which the eastern sand darter feeds (Holm and Mandrak 2000, Vachon 2003, Grandmaison et al. 2004, Gaudreau 2005, NatureServe 2006).
The eastern sand darter is a small fish with limited dispersal ability that exists as a collection of disjunct populations in Canada. Therefore, extirpated populations have little opportunity to be re-established through natural movements.
Reproductive Attributes: The fecundity of the eastern sand darter is low (30–170 mature eggs per female) (Holm and Mandrak 1996), which could contribute to yearly population fluctuations (Facey 1998) and population declines. Females reach sexual maturity at about one year (36 mm SL) and live for over 2 years (Holm and Mandrak 1996, Derosier 2004). Spawning generally occurs at temperatures between 20.5 and 25.5oC (Johnston 1989, Facey 1995, 1998). Based on gonadal examination, Holm and Mandrak (1996) estimated spawning in Ontario to occur between late June and late July. In Illinois, Ohio and Vermont, spawning activity occurs between early April and mid-August (Spreitzer 1979, Johnston 1989, Facey 1995, 1998).
 The definition of ranks appears in Appendix 1.
- Date Modified: