Ninespine Stickleback, Pungitius pungitius

Ninespine stickleback, Pungitius pungitius.

This species has both anadromous and purely freshwater populations. Marine populations remain fairly close to the shore, usually inhabiting low salinity estuaries. This is a common species in much of the Canadian Arctic. It has a circumpolar distribution and, in North America, is found in east and central Canada, Alaska, the Northwest Territories, and Nunavut.

The ninespine stickleback grows to a length of 6 cm. It looks much like the other sticklebacks with its narrow caudal peduncle, usually with a well developed keel on the sides, and a fan-like tail fin with a shallow fork. As its name suggests, there are nine short spines in front of its dorsal fin, but the number can vary from 8–11. There are small bony plates near the front of the stickleback's body, at the base of its dorsal and anal fins, and also on its belly between the pelvic fins. Adults are pale green to dark grey in colour, with darker bars or blotches and a silvery belly. Breeding males turn black underneath and have white pelvic fins.

Spawning occus in fresh water during the summer. While reproduction is a major investment for males, females provide no parental care. After constructing a nest out of aquatic plants, the male uses a string-like secretion from his kidneys to hold it together. The finished nest resembles a tunnel with one or two openings. The female enters the nest, deposits her eggs, and then exits. Although the male courts the female to persuade her to deposit eggs in his nest, he quickly chases her away once the eggs are laid. Entering the nest, he fertilizes the eggs, then guards and protects them, ensuring an adequate oxygen supply by fanning his tail at the entrance to the nest. If his nest reaches capacity – which can be over 600 eggs – he will build a new nest. Males continue to protect their young for about two weeks after hatching. This species lives to a maximum of three years.

The ninespine stickleback feeds primarily on crustaceans, especially freshwater amphipods.