Greenside darter (Etheostoma blennioides) COSEWIC assessment and status report: chapter 5
Habitat
Habitat requirements
The greenside darter is widely distributed in a variety of habitats, but is primarily found in creeks and small to medium rivers with abundant gravel and rubble riffles (Kuehne and Barbour 1983; Page and Burr 1991). It is usually found in the moderate to fast moving water within these riffles (Smith 1979; Lee et al. 1980), and is often associated with vegetation, particularly filamentous green algae in the genus Cladophora (Fahy 1954; Kuehne and Barbour 1983; McCormick and Aspinwall 1983; Page 1983; Bunt et al. 1998). The greenside darter typically inhabits clear streams (Jenkins and Burkhead 1994; Lee et al. 1980), but also appears to thrive in some turbid systems such as the Ausable River, Sydenham River and Thames River in Canada. Poos (2004) found that greenside darter within the Sydenham River inhabited areas with lower turbidity levels. Habitats of rocky substrate highly embedded with fine materials (silt and sand) do not appear to be suitable for greenside darter (Bunt et al. 1998; Stewart and Veliz 2004). Coker et al. (2001) classified the greenside darter as a cool/warmwater species. The greenside darter is absent in shallow headwater habitats in Ohio, especially during the warm summer months, perhaps due to its thermal tolerances (Hlohowskyj and Wissing 1985).
The greenside darter is not restricted to riffle areas of streams although it is most commonly found in these habitats. It also inhabits the shorelines of some large lakes, such as Lake St. Clair in Ontario, and the Ohio waters of Lake Erie, where it occurs around the islands in the western basin and along vegetated habitats on the south shore of the lake (Van Meter and Trautman 1970). Bunt et al. (1998) did not find any greenside darter in the impounded lentic habitat upstream of the Mannheim Weir in the Grand River, Ontario. However, greenside darter have been captured in Guelph Lake, a large impoundment in the same drainage (Reid 2004). The greenside darter is often observed foraging over boulders or submerged logs in pools having little current (Pflieger 1975).
Several authors have investigated microhabitat use by the greenside darter and co-occurring species in stream habitats. Although there are differences between ecosystems, greenside darter tend to prefer larger substrate in riffles than conspecifics (Englert and Seghers 1983; Hlohowskyj and Wissing 1986; Welsh and Perry 1998). Bunt et al. (1998) found greenside darter in the Grand River, Ontario were primarily located on unembedded large cobble and boulder substrate covered with Cladophora spp. Poos (2004) found greenside darter in the Sydenham River in habitats with a high percentage of cobble substrates. Hlohowskyj and Wissing (1986) suggested that the preference for large substrates may be related to their suitability as attachment sites for epilithic algae. The greenside darter also appears to prefer deeper areas of riffle habitats (Fahy 1954; Hlohowskyj and Wissing 1986; Chipps et al. 1993; Stauffer et al. 1996; Grossman and Ratajczak 1998).
Seasonal and age-based differences in microhabitat use can occur in some streams. Grossman and Freeman (1987) found no size-related differences in microhabitat use by greenside darter in a North Carolina stream. In Salmon Creek, New York, Fahy (1954) found that all age-groups of both sexes can be found in riffles throughout the year, but in late fall and winter, juveniles and age I females were also found in quiet water. Schwartz (1965) also stated that greenside darter move into pools during the fall and winter months. Young-of-the-year greenside darter have been reported to use areas with reduced current compared to adults (Pflieger 1975; Smith 1985; Greenberg and Stiles 1993).
Greenside darter normally spawn in swift, rubble-covered riffles where larger rocks are covered with growths of the filamentous algae Cladophora spp. or the moss Fontinalis spp. (Winn 1958a). Eggs are laid directly on the vegetation. Egg deposition has also been reported on milfoil (Myriophyllum sp.) on one occasion (Winn 1958b). Schwartz (1965) reported spawning over fine sand downstream of boulders, and this may also occur in Virginia where the greenside darter is often not associated with vegetation (Jenkins and Burkhead 1994).
Newly hatched larvae probably drift downstream to pools and quiet backwaters immediately downstream of spawning areas. Fahy (1954) did not find larvae on the algae where they hatched, and Baker (1979) captured large numbers of greenside darter larvae in a pool immediately downstream of a spawning riffle.
Habitat trends
Although urban development and agricultural activities have impacted aquatic habitats and have probably contributed to the decline of other aquatic species at risk (fishes and mussels) in the Ausable River, Big Creek, Grand River, Sydenham River, and Thames River watersheds (Nelson et al. 2003; Staton et al. 2003; Portt et al. 2004; Taylor et al. 2004), populations of greenside darter appear to have remained stable or have expanded their range in the face of these changes. All of these watersheds are primarily agricultural, and the Grand River and Thames River have large and growing urban populations. Excessive nutrient enrichment and sedimentation have been identified as problems in most of these watersheds. However, the high nutrient input from agricultural activities may encourage luxuriant growths of filamentous algae that are used as spawning habitat by the greenside darter. All of these watersheds have impoundments, and are subject to extensive agricultural drainage (open and tile drains). The hydrology of the Ausable River has been particularly affected by channel realignments (Nelson et al. 2003). Stewardship and other recovery actions to improve watershed health are ongoing in the Ausable, Grand, Sydenham, and Thames River watersheds as part of watershed-based ecosystem recovery plans for these systems. Habitat in Lake St. Clair changed dramatically after the invasion of zebra mussels (Dreissena polymorpha) in the late 1980s when water clarity and the abundance of aquatic macrophytes increased significantly (Griffiths 1993). These changes associated with the zebra mussel invasion may have improved habitat for greenside darter in the lake. Although there is extensive habitat available for greenside darter in the Detroit River, much of this habitat is degraded or at risk due to historical and current industrial and agricultural activity, as well as urban development (Environment Canada 2003). Remedial Action Plans are currently being implemented for the Detroit River by Canada and the United States as part of the Great Lakes Area of Concern program.
The colonization of five new watersheds by the greenside darter over the last 15 years has resulted in an increase in available habitat. This is particularly true in the Grand River, where the greenside darter now occurs throughout a large portion of the main stem of the river and has colonized 10 tributaries.
Habitat protection/ownership
The habitat of the greenside darter is subject to the general habitat protection provisions of the federal Fisheries Act. Adjacent lands receive policy-level protection through the fish habitat provisions of the Provincial Policy Statement (PPS) under the provincial Planning Act. The PPS prohibits development or site alteration on adjacent lands (within 30 metres (m) of fish habitat) unless it can be shown through an Environmental Impact Study that the fish habitat in question will not be negatively impacted. Recent amendments to the Planning Act now require municipal planning decisions to be consistent with the PPS. The provincial Lakes and Rivers Improvement Act may also indirectly protect greenside darter habitat when applications for the construction or maintenance of dams and dredging activities are reviewed. Aspects of the provincial Nutrient Management Act, Environmental Protection Act, Water Resources Act, and Source Water Protection Act may also provide indirect protection for greenside darter habitat. As a special concern species, there is no federal or provincial species at risk legislation that provides direct habitat protection specifically for the greenside darter.
The beds of the rivers inhabited by the greenside darter are largely owned by the Crown, but the majority of adjacent lands are privately owned and in agricultural production. On the Grand River and Thames River, there are significant portions of adjacent lands in urban areas. The Detroit River population occurs downstream of the large metropolitan area of the cities of Detroit and Windsor. Less than 5% of adjacent lands are in protected areas. Greenside darter habitat or potential habitat occurs within the territories of five First Nations: Six Nations of the Grand River (Grand River); Chippewas of the Thames First Nation, Munsee-Delaware Nation, and Oneida First Nation (Thames River); and Walpole Island First Nation (Lake St. Clair).