Redbreast sunfish (Lepomis auritus) COSEWIC assessment and status report: chapter 4

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Distribution

Global range

The redbreast sunfish can be found east of the Appalachian Mountains from New Brunswick to Florida, and it has been introduced west into Texas, Oklahoma, and Kentucky, including the Mississippi River basin (Figure 2). It has also been introduced and established in areas of Mexico, Puerto Rico, and Italy (Page and Burr 1991; Maitland 2000; Schultz 2004; Scott and Crossman 1998).

Figure 2. The distribution (dark shading) of the redbreast sunfish, Lepomis auritus, in North America (Etnier and Starnes 1993).

Canadian range

In Canada, the redbreast sunfish occurs only in southern New Brunswick, where it is at the northern fringe of its range (Figure 3). It has been documented from eight lakes and seven rivers and streams, all in the lower Saint John River drainage where it has an estimated extent of occurrence of about 25,000 km².

Figure 3. The distribution of redbreast sunfish in eastern Canada (numbered symbols indicate lakes/rivers where the species has been found, not actual capture locations).

The principal populations may be in the Oromocto River drainage where they are found in Oromocto and Yoho lakes, as well as the South Branch of the Oromocto River, the Oromocto River and Rusagonis Stream (Table 1). There are confirmed reports of the redbreast sunfish in the lower Saint John River downstream at Gagetown (Houston 1989, Scott and Crossman 1998, Gautreau and Curry 2006), Swan Creek Lake (DND 2002) and Oram Lake (NBDNR unpublished data). It has also been reported in Anne Lake (also known as Mary Ann Lake), and from the Canaan and Kennebecasis rivers, all of which are in the lower Saint John River drainage (Figure 3).

Redbreast sunfish has also been presumed to occur at a sixth lake, George Lake, as hybrids of redbreast sunfish and pumpkinseed, along with pure pumpkinseed, were recorded from the lake during a two-night sampling period (two fyke nets and 3 windermere traps) in 2001 (DND 2002).

There are additional reports of redbreast sunfish from Modsley Lake in the St. Croix River system and from lakes in the East Musquash drainage near Saint John, NB (see Houston 1989). There are no vouchers to verify these collections and no additional specimens have since been collected; therefore, these records are deemed questionable. However, redbreast sunfish have been confirmed in the American portion of the St. Croix drainage (Big Lake, Maine); but the species has not been observed and/or confirmed elsewhere in the St. Croix River system where it borders New Brunswick.

The redbreast sunfish is considered to be a largely sedentary species that seldom moves more than a few metres of capture sites over extended (six months or more) periods (Gatz and Adams 1994). Occurrences are based on evidence of historic and current presence at a given location. Dams, impassable falls, and upland habitat provide separation barriers and elemental or separation distance is taken to be 10 km regardless of habitat quality (NatureServe 2007). In general, each occupied river segment that is undivided by a barrier is treated as a single occurrence or location, regardless of the distance between observation/collection sites, and may therefore include multiple tributaries(Hammerson 2001 as cited in NatureServe 2007).

Given the uncertainties about the full extent of its distribution in the province, and its continued existence in some previously documented locations (see Population Sizes and Trends), it is impossible to determine with any certainty the current area of occupancy of the species. Based on habitat requirements (see Habitat) and what is known about movement/dispersal of the species, the actual amount of aquatic habitat available to the species (sum of stream width x distance, lake areas) as measured from the appropriate 1:50 000 topographical maps would be less than 1500 km². Based on an overlaid grid of cells one km², total area of occupancy (the number of squares that are intersected by freshwater lakes and/or rivers/streams provides an estimate of 2800 km² (assuming the species is extant at all previously known locations).

As noted by Houston (1989), the redbreast sunfish has occasionally been mistaken for the pumpkinseed, a source of confusion which underlines the need to be cautious in interpreting historical reports, but which also points to the possibility of redbreast sunfish as having been overlooked in some fish surveys. The occurrence of natural hybrids with pumpkinseed, a more common species in southern New Brunswick, is an additional source of difficulty in identification.