Redbreast sunfish (Lepomis auritus) COSEWIC assessment and status report: chapter 5

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Habitat

Habitat requirements

There appears to be little in the literature to identify redbreast sunfish habitat in more than a generalized manner. Houston (1989) suggests that they may be adapted to a wide range of habitats. In streams they appear to inhabit areas of slower flow, pools and backwaters that are generally over rock or gravel substrates (Scott and Crossman 1998). In lakes, they can be found in vegetated areas with substrates ranging from sand to mud (Scott and Crossman 1998). The results of fall sampling in Yoho Lake, NB, were consistent with this general description for lacustrine habitat, with the highest rate of capture occurring in the vicinity of large woody debris, beaver lodges, and dense submerged and emergent vegetation (Gautreau and Curry 2006). More specific information on nesting behaviour suggests that redbreast sunfish require open areas, often with some protective structure nearby (Gautreau and Curry 2006). It appears that it may also be able to spawn in brackish, tidal waters (Richmond 1940).

Whittier et al. (1999) detected redbreast sunfish in 14% of the 203 randomly selected lakes (≥ 1 ha to < 1000 ha) that they surveyed in the northeastern United States. Although sunfish were usually found in the larger, deeper lakes sampled, four of the five New Brunswick lakes known to have this species would be from the smaller end of the sample spectrum (i.e., < 200 ha: Table 2).

Whittier et al. (1999) also suggest that redbreast sunfish may be less tolerant of acidic and eutrophic conditions than are other centrachids (bass and sunfish) of the region. They present a pH range of 7.0 to 7.5 (2^nd and 3^rdquartiles, with extreme values from roughly 5.5 to 8.5). However, in Georgia, the species is apparently found in streams with pH ranging from 4.5 to 6.0 (Coomer et al.1977). In New Brunswick, detailed water quality data are available for only one of the five lakes with redbreast sunfish. Yoho Lake has a surface area of 131 ha and is described as mesotrophic. Water data collected at different intervals between 1975 and 1991 indicate a consistent median pH of approximately 6.6 over that time (range in Median from 6.5 –6.81; range in sample values from 6.1 to 7.0).

The scant information on nutrient load is more consistent across reports, with total phosphorus values comparable between the samples of Whittier et al. (1999) in the northeastern United States (range - < 5 > 10µg/l) and Yoho Lake (< 10 µg/l: Table 3), respectively.

In New Brunswick, redbreast sunfish have also been documented from riverine habitats, varying in order from the relatively small Rusagonis Stream to the main stem of the Saint John River.

Habitat trends 

A direct measure of habitat trends for redbreast sunfish is not currently feasible, given the general nature of the habitat description and the lack of information on the distribution of the species within most of the lakes and rivers from which it has been reported in New Brunswick. The recent studies of Yoho and Oromocto lakes (Gautreau and Curry 2006) are the first surveys to provide baseline data on the species habitat in the province. However, a cursory analysis of orthophotos (scale 1:10,000, aerial photography from 2002) was used to identify the sites that have been or continue to be the most susceptible to habitat loss (Table 2).

Of the New Brunswick lakes with redbreast sunfish, Yoho Lake is unique in the extent of shoreline development, with almost the entire periphery devoted to cottages, or year-round residences. This development boom prompted monitoring of water quality by the New Brunswick Department of the Environment from 1975 to 1991. Parameters studied over that period included pH, alkalinity, conductivity, hardness, bacterial levels, productivity, total phosphorus, sodium, potassium, nitrates and nitrites, suspended solids and several metals including, Fe, Mn, Cu, Pb, Zn, Cd, and Al (NB Department of Environment 1991). In addition, temperature and dissolved profiles were compared at four intervals during this study. No significant trends were detected in these parameters over time, though slight increases were noted in total phosphorus (Table 3). Development or other pressures on the remaining four lakes did not approach the levels observed at Yoho Lake (Table 2).

A similar orthophoto analysis was conducted for the rivers and streams with redbreast sunfish. A four-kilometre stretch of shoreline was characterized, consisting of two kilometres upstream and two kilometres downstream of the presumed location of collection (Table 2). However, almost the entire length of Rusagonis Stream was examined, but the Kennebecasis River was omitted from the analysis altogether, due to the lack of a specific location for the collections on these two watercourses. The Rusagonis Stream was identified as the most susceptible or altered of the watercourses examined. The Kennebecasis is likely to have also been identified as vulnerable due to the development pressures and agricultural activity along its valley. Unfortunately, the lack of recent data on the redbreast sunfish from these watercourses makes it impossible to determine if development and agricultural pressures have had an impact on the species.

Habitat protection/ownership 

The shores of most of the lakes and rivers with redbreast sunfish are subject to the influence of multiple landowners, including the Crown. However, much of the land bordering the Oromocto River and Swan Creek Lake is under the control of the Department of National Defense (DND). Canadian Forces Base, Gagetown encompasses much of the Oromocto River and Swan Creek Lake, and the potential site at George Lake falls entirely within its borders.

The reported occurrences in the East Musquash lakes are within the Loch Alva Protected Area, as well as being part of the protected water reserves for the City of Saint John.

Aquatic habitats in New Brunswick are protected under the federal Fisheries Act and provincial legislation, including the Clean Environment Act, Crown Lands and Forest Act, and Clean Water Act.