Giant Threespine Stickleback
Scientific Name: Gasterosteus aculeatus
Other/Previous Names: Giant Stickleback ,Gasterosteus sp.
Taxonomy Group: Fishes
Range: British Columbia
Last COSEWIC Assessment: November 2013
Last COSEWIC Designation: Special Concern
SARA Status: Schedule 3, Special Concern - (SARA Schedule 1 provisions do not apply)
Image of Giant Threespine Stickleback
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 the 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.
Distribution and Population
The Giant Threespine Stickleback occurs only within Mayer and Drizzle lakes on Graham Island, Haida Gwaii, British Columbia. The number of mature individuals is thought to be in the high tens of thousands for Mayer Lake, and greater than 100,000 for Drizzle Lake.
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 this lake. The Giant Threespine Stickleback spends spring and summer in near-shore areas for spawning, and moves to deeper waters in winter.
The reproductive biology of the Giant Threespine Stickleback is generally thought to be similar to other freshwater Threespine Stickleback, where males build nests and provide care to fry. The male Giant Threespine Stickleback reaches maturity at approximately two (Mayer Lake) or three years (Drizzle Lake). The breeding season typically lasts from early May to mid-August. Males breed up to five times within a given breeding season. Females lay ~250 eggs in Mayer Lake and ~400 eggs per clutch in Drizzle Lake. Main predators in both lakes include Coastal Cutthroat Trout, and the Common Loon, among several other bird species. Giant Threespine Sticklebacks typically live up to four years in Mayer Lake and eight years in Drizzle Lake.
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
The Giant Threespine Stickleback 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 (http://www.sararegistry.gc.ca/).
Provincial and Territorial Protection
PLEASE NOTE: Not all COSEWIC reports are currently available on the SARA Public Registry. Most of the reports not yet available are status reports for species assessed by COSEWIC prior to May 2002. Other COSEWIC reports not yet available may include those species assessed as Extinct, Data Deficient or Not at Risk. In the meantime, they are available on request from the COSEWIC Secretariat.
4 record(s) found.
- COSEWIC Status Reports (1 record(s) found.)
- Response Statements (1 record(s) found.)
- COSEWIC Annual Reports (1 record(s) found.)
- Consultation Documents (1 record(s) found.)
COSEWIC Status Reports
COSEWIC Annual Reports
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