Unarmoured Threespine Stickleback
Scientific Name: Gasterosteus aculeatus
Other/Previous Names: Charlotte Unarmoured Stickleback,Charlotte Unarmoured Sticklebacks,Charlotte Unarmoured Threespine Stickleback ,Gasterosteus aculeatus,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 Unarmoured Threespine Stickleback
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.
Distribution and Population
The Unarmoured Threespine Stickleback occurs only within Boulton, Rouge, and Serendipity lakes on Graham Island, Haida Gwaii, British Columbia. The number of mature individuals is thought to be in the high thousands for Rouge Lake, the low tens of thousands for Serendipity Lake, and the low hundreds of thousands for Boulton 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. Boulton, Rouge, and Serendipity lakes are small, shallow, acidic water bodies, surrounded by Sphagnum spp. bog and scrub coniferous forest. 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.
Little is known of the reproductive biology of the Unarmoured Threespine Stickleback; however, it is thought to be similar to other freshwater Threespine Sticklebacks. Unarmoured Threespine Sticklebacks reach maturity at approximately three years of age, and females lay clutches of 100-300 eggs each. Likely predators include macroinvertebrates such as leeches and nymphs, the Common Loon, Belted Kingfisher, and several species of grebes and mergansers. Unique aspects of their biology include an unusual tolerance of acidic water, and a symbiotic relationship with parasites found in Rouge Lake. Threespine Sticklebacks typically live to between two to three years of age.
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.
The Unarmoured 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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