Aquatic Species at Risk - Rocky Mountain Sculpin (Eastslope populations)

Description
Habitat
Threats
Further Information
Scientific Information

Description

Illustration of a Rocky Mountain Sculpin

 © Joseph R. Tomelleri

The Rocky Mountain Sculpin (Eastslope populations) (Cottus sp.), also known as the Eastslope Sculpin or St. Mary Sculpin, is a small bottom-dwelling freshwater fish. It is a member of the Cottidae family and has the following characteristics:

• Large head;
• Body is heavy and tapers from the head to the tail;
• Does not have an air bladder;
• First dorsal and pelvic fins have protective spines;and
• Maximum fork length is 114 mm (Milk River).

Habitat

The Rocky Mountain Sculpin has a very limited distribution, found only in the Milk and St. Mary river watersheds in Alberta, Montana and Wyoming (upper Missouri River system), and possibly the Flathead River in British Columbia. In Alberta, the Rocky Mountain Sculpin distribution (i.e. the Eastslope populations) is limited to the St. Mary River system above the St. Mary Reservoir, and the upper Milk and North Milk rivers. In the St. Mary River system, distribution is limited to the lower 35 km of Lee Creek, the lower 500 m of Aetna Creek, and the St. Mary River upstream of the St. Mary Reservoir. Distribution also extends from the North Milk River at the Alberta/Montana border, downstream to its confluence with the Milk River, and within the Milk River, downstream to within 85 km of the international border.

The Rocky Mountain Sculpin is found in cool, clear streams with shallow runs and riffles, rock, gravel or cobble substrate. It is usually absent from pools with bottoms of clay or sand. It is nocturnal and remains under cover during the day. Life history information on the Rocky Mountain Sculpin is very limited. Both sexes are believed to be sexually mature by 23 months of age. Spawning occurs in late spring at temperatures between 7.5° and 15°C. The fecundity generally ranges from 100 to 700 eggs, which hatch within two-to-three weeks, depending on the temperature. The young-of-the-year are 30-to-40 mm in total length by the end of their first summer and yearlings are about 50 mm. This fish does not appear to migrate. Longevity is likely less than five years.

Threats

The greatest threat to the Rocky Mountain Sculpin (Eastslope populations) of the St. Mary and Milk River watersheds is habitat alteration or loss due to the reduction of flowing water. This may be caused by impoundment of water in reservoirs, diversions and water removal for irrigation. In addition, low water flow results from the frequent and extreme droughts that southern Alberta experiences during the summer. Other undesirable changes to sculpin habitat include elevated water temperature, increased siltation of substrate and loss of riffle habitat.

Further Information:

For further information, visit the SARA Registry at www.SARAregistry.gc.ca or www.COSEWIC.gc.ca

Scientific Information:

Scientific name: (Cottus bairdii)
SARA Status: Threatened (September 2006)
COSEWIC Status: Threatened (May 2005)