Giant 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 Giant Threespine Stickleback is a 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. Key features of the Giant Threespine Stickleback's appearance include its unusually large size (~80-85 mm length), a streamlined body, a greater number of gill rakers and bony plates on the sides of its body, longer pelvic spines, and black colouration with silver shading and dark flank bars. Breeding colouration of these fish is unusually dark compared to the more typical red breeding colouration observed in other stickleback species.

Habitat

The Giant Threespine Stickleback occurs only within Mayer and Drizzle lakes on Graham Island, Haida Gwaii, British Columbia. 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. Mayer and Drizzle lakes are shallow, acidic, and darkly stained water bodies located in lowlands consisting primarily of Sphagnum spp. bogs and coniferous forest.

Mayer Lake has three inlets (Cott, Woodpile, and Gold Creeks) and an outlet (Mayer River) flowing to the Pacific Ocean. Near-shore habitat typically consists of gently sloping sand or pebbles with patchy vegetation. Drizzle Lake has an inlet stream, and an outlet stream, which drains to the Pacific Ocean. The lake-bottom typically consists of sand and gravel, with some pebbles occurring closer to shore. Calcium levels are particularly low, and aquatic vegetation is sparse in Drizzle Lake. The Giant Threespine Stickleback spends spring and summer in near-shore areas for spawning, and moves to deeper waters in winter.

Threats

The key threat to the Giant Threespine Stickleback is the introduction of invasive species. Other threats include changes in predation regimes (e.g. from Coastal Cutthroat Trout and/or the Common Loon), human disturbance (e.g. forestry operations), and potentially, habitat changes caused by introduced beavers.

Further Information

The Giant Threespine Stickleback is being considered for listing under the federal Species at Risk Act (SARA) as Special Concern.

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

Visit the Species at Risk (SARA) Public Registry Profile.

Giant Threespine Stickleback

Giant Threespine Stickleback

Photo credit: Dr. T. E. Reimchen

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

Did You Know?

Giant Threespine Sticklebacks in Mayer Lake can reach over 100 mm in length—this is the largest known size of Threespine Stickleback throughout its northern distribution.

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