Unarmoured Threespine Stickleback

Gasterosteus aculeatus

SARA Status
No Status
NS
Special Concern
SC
Threatened
TH
Endangered
EN
Extirpated
EX

SARA Status

  • No Status NS
  • Special Concern SC
  • Threatened TH
  • Endangered EN
  • Extirpated EX
COSEWIC Status
Not at Risk
NR
Special Concern
SC
Threatened
TH
Endangered
EN
Extirpated
EX

COSEWIC Status

  • Not at Risk NR
  • Special Concern SC
  • Threatened TH
  • Endangered EN
  • Extirpated EX

Description

The Unarmoured Threespine Stickleback, also known as the Charlotte Unarmoured Stickleback, is a small (~65 mm length) freshwater fish, likely descended from the marine Threespine Stickleback (Gasterosteus aculeatus). Freshwater Threespine Sticklebacks typically have three dorsal spines, an anal spine, two pelvic spines and bony plates on the sides of their bodies. A key feature of Unarmoured Threespine Stickleback's appearance is the loss of one or more of the typical dorsal spines, and the reduction or absence of bony plates on the sides of their bodies.

Habitat

The Unarmoured Threespine Stickleback occurs only within Boulton, Rouge, and Serendipity lakes on Graham Island, Haida Gwaii, British Columbia. Boulton, Rouge, and Serendipity lakes are small, shallow, acidic water bodies, surrounded by Sphagnum spp. bog and scrub coniferous forest. In general, the species likely requires: sustained productivity in open water and near-shore habitats, including natural near-shore vegetation; absence of invasive species; and gently sloping sand/gravel beaches.

Boulton Lake is mainly fed by groundwater seepage and has an intermittent outlet to the Pacific Ocean. The lake-bottom consists of varying materials including thick organic ooze, sand, and gravel. Its water is relatively clearer than Rouge and Serendipity lakes. In Boulton Lake, adult females are primarily found in open waters in spring and summer, while adult males typically remain near shore to nest; both sexes move to deeper water in the winter. Rouge Lake is smaller, shallower, and more acidic than Boulton Lake; its lake-bottom consists primarily of organic ooze and sand. Serendipity Lake is similar in size, depth, and acidity to Rouge Lake; its lake-bottom consists primarily of thick organic ooze. Both Rouge and Serendipity lakes are mainly fed by groundwater seepage; their outflows are blocked by beaver dams.

Threats

The key threat to the Unarmoured Threespine Stickleback is the introduction of invasive species. Other threats include changes in predator regimes, human disturbance (e.g. rural and industrial activities), erosion, severe winter conditions and potentially, habitat changes caused by introduced beavers.

Further Information

The Unarmoured Threespine Stickleback species is being considered for listing under the federal Species at Risk Act (SARA) as Special Concern. More information about SARA, including how it protects individual species, is available on the Species at Risk Public Registry.

To find out if this species is protected by provincial laws, consult the Province of British Columbia's website.

Unarmoured Threespine Stickleback

Unarmoured Threespine Stickleback

Photo credit: Dr. T. E. Reimchen

Scientific Name: Gasterosteus aculeatus
SARA Status: Special Concern
COSEWIC Status: Special Concern (2013)
Region: British Columbia

Did You Know?

Unarmoured Threespine Sticklebacks are unusually tolerant to acidic waters; in Serendipity Lake, pH levels can be as low as 3.9.

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