Three-Spined Stickleback

Author: Anil Mishra 

Photos: Anil Mishra and D. Young

Common Name: Three-Spined Stickleback

Scientific Name: Gasterosteus aculeatus

Size range: 5-10 cm 

Habitat: The Three-Spined Stickleback can be commonly found in British Columbia but they have also been found in the Bering Sea, Northern California, and parts of East Asia. They can tolerate many water conditions and may live in fresh water lakes, ponds and ditches, brackish water, as well as in the ocean.  They are often found in schools in shallow water along docks in the Pacific Northwest. 

Food (Prey): The main diet of the Three-Spined Stickleback in fresh water are water fleas mayfly larvae, and sometimes smaller fish.  In the ocean they eat a variety of small plankton and invertebrates such as copepods. 

Predators: Bigger fish will try to catch the Three-Spined Sticklebacks but the Stickleback’s armour can protect them. The Three-Spined Stickleback is also pretty aggressive and will fight off predators which can result in some bigger fish avoiding them.

Identifying Features: The Three-Spined Stickleback has 3 pointed spines at the top, bony plates on the side that act as armour, and a spine in the pelvic fin. It is usually coloured silver, green, blue or  black but in freshwater they are usually brown.  During breeding the males’ throat region becomes bright red and the eyes a striking blue. 

Illustration by D. Young

Behaviour: The Three-Spined Stickleback are actually pretty social and will sometimes join groups of fish that look similar to them.  They are often studied for their behaviour during courtship, mating and when protecting their territory. 


Gotshall, D. (2001). Pacific Coast inshore fishes. Sea Challengers, Incorporated.

Lamb, A., & Edgell, P. (2010). Coastal Fishes of the Pacific Northwest Revised and Expanded Second Edition. Harbour Pub.

Lamb, A., Lamb, A., & Edgell, P. (1986). Coastal Fishes of the Pacific Northwest. Harbour Publishing.

Threespine stickleback. (n.d.). Wisconsin Sea Grant. Retrieved January 24, 2024, from 

Wood, S. (2020). ADW: Gasterosteus aculeatus: INFORMATION. Animal Diversity Web. Retrieved January 15, 2024, from 

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