Gasterosteus aculeatus

Identification Tips:

•Freshwater forms usually mottled brown or greenish; ocean forms silvery green to bluish black.
•Breeding males become bright blue or green with blue or green eyes, and bright red or orange breast
•Dorsal fin: 3 to 4 stiff spines and 10-14 soft rays; Spines separated from each other and from the soft-rayed fin,
•Anal fin: 1 spine and 8 - 10 soft rays
•Pelvic fins: 1 prominent spine
•Caudal fin with 12 rays.
•Series of plates along the sides of the body; Ocean form is fully plated, freshwater forms less so.

Conservation Status:

British ColumbiaCanadaNatureserve
COSEWICSpecies at Risk Act
Not at Risk (Yellow List)Not AssessedNoneG5, S5

Information Source: BC Conservation Data Centre:

Life History:

•Notorious for variation among populations in body form, behaviour and life history.
•Some unique and endangered forms in coastal lakes and streams, but none known from Fraser Valley,
•Fraser Valley has resident freshwater forms and populations that migrate up to 150 km inland from the sea to spawn in spring.
•Forms schools except when breeding.
•Feeds primarily on small invertebrates, but also eggs and small fish.
•Breed in spring and summer
•Males build nests of vegetation and entice females to spawn with elaborate courtship behaviour.
•Males often breed with several females and defend eggs and fry
•Most adults are 1 or 2 years old, some may live up to 4 years.
•Maximum length in freshwater is 8 cm while in saltwater is 11 cm.


•Found in almost all waters of the Fraser Valley that contain fish, including fresh water, estuary and inshore coastal seas.
•Prefers shallow vegetated areas, usually over mud or sand.


British Columbia
•All coastal drainages including Vancouver Island and Haida Gwaii

•Coastal and adjacent freshwater habitats in arctic and temperate waters of northern hemisphere north of 30 to 35 deg. latitude.
•North America, Europe, North Africa, Russia, Eastern Asia north of Japan, Greenland.

Primary Information Source:
McPhail, J.D. 2007. The Freshwater Fishes of British Columbia. University of Alberta Press. Edmonton, Alberta.