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COSEWIC Assessment and Update Status Report on the Redbreast Sunfish (Lepomis Auritus) in Canada

Population Sizes and Trends

Search effort 

The species has apparently been known in New Brunswick since at least 1896 (Cox 1896; Scott and Crossman 1998), with the first bona fide record in 1948 (Scott and Crossman 1998). Houston (1989) speculated that the scarcity of records (Table 1) might have been due to natural rarity, confusion with the pumpkinseed, lack of interest in the species, or a combination of these factors. Recent collection efforts suggest the latter.

There are approximately 796 lakes or ponds > 1 ha in area within the range of the redbreast sunfish in southwestern New Brunswick (total area = 24,742 km²). Data records at the New Brunswick Department of Natural Resources (NBDNR) and New Brunswick Cooperative Fish and Wildlife Research Unit (NBFWRU) show fish population information on 227 of these water-bodies, and redbreast sunfish are known from only eight of these lakes (Table 1 and Figure 3). It should be noted that the lack of recorded occurrences does not guarantee absence of the species from all of these waters. NBDNR biologists suggest that gear types used during sampling (e.g., variable mesh experimental gill nets, fyke nets), would be effective in capturing redbreast sunfish if they were in the area sampled. However, it is also important to note that, at Oromocto Lake, sampling locations in close proximity (i.e. within 1 km), with similar habitat types, may or may not have redbreast sunfish, indicating localization of populations.

The Saint John River has been extensively sampled for fish species of recreational interest. However, the only records of redbreast sunfish from the main stem of the river resulted from recent sampling that targeted this species. Given what is believed to be the localized nature of sunfish populations, it is possible that additional populations on the river have escaped detection. These collections have yielded redbreast sunfish at two sites in the main river downstream of Fredericton, and in the Oromocto River system (Table 1 and Figure 3). Records for four other lower Saint John River tributaries (Table 1), Modsley Lake (St. Croix River), Knockdrin and Shadow lakes (East Musquash River) have not been recently re-confirmed.

Abundance

Yoho Lake is the only New Brunswick population of redbreast sunfish for which population estimates are available. A mark-recapture study conducted in September 2005 yielded a population estimate, based on the Schnabel Method, of 325 (C.I. 186-630) [Gautreau and Curry 2006], and 447 (C.I. 235-1006) in 2006 (Gautreau and Curry unpubl. data). In 2007, an estimate of 743 (C.I. 253-1233) was derived using 2006 marks and the Peterson Method (Gautreau and Curry unpubl. data). The area targeted for the estimates was approximately 8.9 ha. While it is not possible to determine if there have been declines in the redbreast sunfish population over this period, the abundance estimates from Gautreau and Curry (2006; unpubl. data) indicate a sizable population of the species within the lake.

Additional observations suggest that the redbreast sunfish is abundant in Oram Lake (NBDNR unpubl. data) and common in Anne Lake (NBFWRU unpubl. data). Further, redbreast sunfish has been detected in Oromocto Lake over multiple survey years, suggesting the presence of a robust population.

In the Saint John River downstream of Gagetown, five redbreast sunfish were captured over a two-day sampling, which targeted all species, using gear types that would likely catch redbreast sunfish.

Fluctuations and trends

Data on the long-term trends in population sizes is not available. Sampling in 2005 represents the first focused research for the redbreast sunfish in Canada. In Oromocto and Yoho lakes, the species is readily captured over suitable habitats when using appropriate gear types. Its continuing presence in the Canaan and Kennebecasis rivers, Modsley, Knockdrin and Shadow lakes is yet to be confirmed.

Rescue effect

Given the successful establishment of the species outside its native range, the potential for reintroduction or enhancement from other populations is possible as long as suitable habitat is available. It is unlikely that natural immigration from outside Canada would occur for this non-migratory species.