Greenside darter (Etheostoma blennioides) COSEWIC assessment and status report chapter 4

Distribution

Global range

The greenside darter occurs in drainages of the lower Great Lakes (southern Lake Huron, Lake Erie and southern Lake Ontario) and the Mississippi River from New York and Maryland west to eastern Kansas and Oklahoma, and from Ontario south to Georgia, Alabama and Arkansas (Lee et al. 1980, Page and Burr 1991) (Figure 3). The species is also found in the Mohawk, Susquehanna and Potomac River drainages of the Atlantic Slope from New York south to Virginia. There is a hiatus in the southern portion of the range, with a disjunct segment occurring in Kansas, Missouri, Arkansas and Oklahoma. Although Schwartz (1965) considered the Potomac River to be part of the native distribution of the greenside darter, Jenkins and Burkhead (1994) concluded that it was introduced given its relatively recent discovery (late 1950s) and ongoing range expansion within this watershed. Its presence in the Susquehanna River drainage (where it was first recorded in 1962) is believed to be the result of stream capture from the Allegheney River drainage (Denoncourt et al. 1977). The greenside darter occurred historically in 19 states, the District of Columbia and Ontario (NatureServe 2006). It has been extirpated from several American streams, but its overall range has not changed significantly. The species is ranked as SH (historic – no verified records within the last 20 years) in the District of Columbia (NatureServe 2006).

Figure 3. Global range of the greenside darter, Etheostoma blennioides.

Figure 3. Global range of the greenside darter, Etheostoma blennioides.

Canadian range

The greenside darter is only known in Canada from southwestern Ontario where it occurs in tributaries to Lake Huron, Lake St. Clair and Lake Erie (Figure 4). The Canadian distribution represents less than 5% of the global range of the greenside darter. When the status of the greenside darter was initially assessed by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in 1990, it was known from the Ausable River (southern Lake Huron drainage), Sydenham River, Thames River, Lake St. Clair (Lake St. Clair drainage) and Big Creek (Lake Erie drainage) (Dalton 1991). Dalton (1991) mistakenly mapped a 1975 record from Gold Creek as being near the city of Sarnia at the southern tip of Lake Huron. The Gold Creek in question is actually in the Sydenham River watershed in the vicinity of the town of Strathroy. Since the status of the species was last assessed 1990, its presence has been confirmed in all of the Canadian watersheds, and at most locations where it was captured historically (Figure 4). The range of the greenside darter within the Ausable River and the Sydenham River appears to have expanded since 1990. This is likely a combination of increased sampling effort (particularly in smaller tributaries) as well as actual range expansion.

Figure 4. Canadian range of the greenside darter, Etheostoma blennioides.

Figure 4. Canadian range of the greenside darter, Etheostoma blennioides.

The greenside darter has been reported in five new watersheds since its status was last assessed in 1990.  The greenside darter was collected from the Grand River watershed of the Lake Erie drainage for the first time, and it has since colonized much of this watershed (Figure 5). Evidence strongly suggests that this is an introduced population (see Population sizes and trends). In 1998, four juvenile greenside darter (43-46 millimetres (mm)) were reported from a single site on Big Otter Creek (Lake Erie drainage). Although there are no voucher specimens to confirm this record, the sampling crew was knowledgeable and was familiar with the species (S. Gibson, personal communication (pers. comm.) 2005). Intensive sampling at numerous sites in Big Otter Creek during 2002 and 2003 (D. Depasquale, pers. comm. 2005), and sampling by the author at three different sites in the vicinity of the 1998 collection in fall 2004, did not capture any greenside darter. In 2002, two greenside darter were collected from the Bayfield River by Fisheries and Oceans Canada (DFO), and one was deposited in the Royal Ontario Museum ( ROM 75857). It is possible that the individual greenside darter in these two systems may have naturally dispersed from adjacent river systems (Big Creek and Ausable River respectively). The greenside darter was found in the Canadian waters of the Detroit River (Ruwe Marsh) for the first time in 1995 (Tulen et al. 1998). Significant sampling effort in the Canadian waters of the Detroit River in 2003 and 2004 did not capture any greenside darter (Lapointe 2005, N.E. Mandrak, unpubl. data). It is possible that the species was always present, but not detected, or that it dispersed from the American waters of the Detroit River or downstream from Lake St. Clair. In the fall of 2005, several greenside darter were captured in Pefferlaw Brook of the Lake Simcoe drainage (J. Barnucz, pers. comm. 2005), during surveys conducted prior to treatment with rotenone to eradicate a population of introduced round goby (Neogobius melanostomus). The round goby was presumed to be introduced via a baitfish holding pond adjacent to the stream, and it is likely that greenside darter was introduced to this stream via the same mechanism. This location is more than 100 km northeast of the closest greenside darter population in the Grand River. Given its distinctive appearance, it is highly unlikely that the greenside darter would have been misidentified in earlier collections in these five watersheds. Further sampling is required to determine if populations are established in these watersheds, and if they are more widespread.It is quite possible that the Pefferlaw Brook population was extirpated by the 2005 rotenone treatment. A survey conducted in 2006 did not collect any greenside darter (N. Mandrak, pers. comm. 2006).

The extent of occurrence of the greenside darter in Canada is approximately 38,400 square kilomtres (km²). The current area of occupancy is estimated to be 33 km² (both area values estimated from Figure 4). It is difficult to determine the number of locations for the greenside darter in Canada. The species has been captured at hundreds of sites in at least ten tertiary watersheds. The Natural Heritage Information Centre (NHIC) recognizes 76 extant and historical element occurrences within these watersheds (NHIC 2005).

Figure 5. Spread of the greenside darter, Etheostoma blennioides, in the Grand River watershed between 1990 and 2005. Upper left map shows fish sampling effort in the watershed prior to the first discovery of greenside darter in 1990.

Figure 5. Spread of the greenside darter, Etheostoma blennioides, in the Grand Riverwatershed between 1990 and 2005. Upper left map shows fish sampling effort in the watershed prior to the first discovery of greenside darter in 1990.

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