. The Canadian field-naturalist. 214 The Canadian Field-Naturalist Vol. 114 Nipigon River, â¦^ Little Cypress River â, , ^ .^ ^ 1 Little Pic River Black Bay Thunder Bay â T* 1987 Marathon Black River. Poplar River Taconite Harbor ⢠Gasterosteus aculeatus ⦠Apeltes quadracus 100 km Figure 1. Location of collection of specimens of Gasterosteus aculeatus and Apeltes quadracus from Lake Superior. Map shows probable and known progression of Gasterosteus from 1987-1996. lected in the Nipigon River (48°57'N, 88°14'W) (Lake Superior Programs Office 1996). An addition- al 22 individuals were collec
. The Canadian field-naturalist. 214 The Canadian Field-Naturalist Vol. 114 Nipigon River, â¦^ Little Cypress River â, , ^ .^ ^ 1 Little Pic River Black Bay Thunder Bay â T* 1987 Marathon Black River. Poplar River Taconite Harbor ⢠Gasterosteus aculeatus ⦠Apeltes quadracus 100 km Figure 1. Location of collection of specimens of Gasterosteus aculeatus and Apeltes quadracus from Lake Superior. Map shows probable and known progression of Gasterosteus from 1987-1996. lected in the Nipigon River (48°57'N, 88°14'W) (Lake Superior Programs Office 1996). An addition- al 22 individuals were collected by a biological con- sultant in the Black River (48°38'N, 86°16'W) and identified by us in 1995. We collected a specimen from Black Bay (48°40'N, 88°25'W) in 1996. One specimen was captured at the mouth of the Little Cypress River (48°56'N, 87°51'W) in 1997 (Stephenson 1998) and two more were captured in the Little Pic River (48°59'N, 86°45'W) and identi- fied by us in 1998. The last three collections suggest that Gasterosteus is now well established between Thunder Bay and the Black River. Since its introduction, Apeltes has been collected at only two additional Lake Superior locations. A single specimen was collected with the Gasterosteus specimens in the Black River in 1995. Three speci- mens were also collected from the Nipigon River in 1995 (Lake Superior Programs Office 1996). There are no reports of Apeltes from waters. Discussion While the relative abundance of all native species will exhibit a decrease in abundance due to the increase in frequency of the invading species, the rapid increase in Apeltes. especially in very nearshore areas, suggests it is displacing native stick- lebacks at a rapid rate. In just over ten years, Apeltes has become the dominant stickleback species collect- ed at Mission Marsh and is the only stickleback species collected on an annual basis (Table 2). Fall seining has most often captured Apeltes i
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