Ninespine stickleback
Small freshwater fish with variable spines found across the Northern Hemisphere.
The ninespine stickleback is a small, scaleless fish inhabiting temperate waters across Eurasia and North America. It adapts to both marine and freshwater environments, showing distinct physiological traits in isolated pond populations.
- Spine count varies from seven to twelve, not always nine.
- Males build nests on waterweed and guard the eggs.
- Cannot gulp air due to lacking a swim bladder connection.
- Found in both freshwater and marine habitats in high latitudes.
- Lives up to three years and reaches 12.5 cm in length.
What it is
This small fish reaches a maximum length of roughly 12.5 centimetres. Its body tapers to a narrow tail stalk with a fan-shaped fin. Unlike many relatives, it lacks scales but possesses small bony plates near the tail. The mouth points upward, and the colour ranges from greyish or olive-brown to silvery flanks with dark bars. Males develop black pelvic areas and white spines during breeding season. The number of spines before the dorsal fin varies between seven and twelve, though nine is most common.
Where it lives
The species inhabits temperate zones across the Northern Hemisphere. In North America, it lives in systems draining into the Arctic and Atlantic Oceans, ranging from Alaska and Canada south to New Jersey. It also occurs on the Pacific coast of Alaska and within the Great Lakes basin. Across Eurasia, its range includes the United Kingdom, Greenland, Turkey, and the Far East. It thrives in streams, lakes, ponds, and rivers, often favouring thick submerged vegetation for protection.
How it lives
These fish are euryhaline and eurythermal, meaning they tolerate varying salt levels and temperatures. Marine populations show reduced metabolic rates in cold conditions and larger livers relative to body mass compared to freshwater groups. Freshwater pond dwellers can survive temperatures between six and nineteen degrees Celsius by adjusting their metabolism. As physoclists, they lack a direct link between the swim bladder and gut, preventing them from gulping air. Instead, they use aquatic surface respiration to breathe oxygen-rich surface water when dissolved oxygen levels drop.
Breeding and life cycle
Spawning occurs from April to July. The male constructs a nest suspended on waterweed just above the lake or river bed. He attracts a female, who deposits eggs inside before leaving. The male then assumes full parental responsibility, guarding the eggs and newly hatched fry. Once the young develop their protective spines, the father drives them away to live independently. This behaviour ensures the offspring have some defence before facing the wider environment alone.
Fish and people
Scientific interest in this species grew through studies of its behaviour and physiology. Zoologist Desmond Morris published research on its reproductive habits in 1952, which formed part of his doctoral thesis at Oxford University. His work examined normal mating patterns and variant behaviours under the guidance of ethologist Niko Tinbergen. These studies contributed to broader discussions on animal behaviour and its potential parallels with human actions, as detailed in later publications.
Questions people ask about Ninespine stickleback
Why is it called the ninespine stickleback if the spine count varies?
The name refers to the most common number of spines found in front of the dorsal fin. However, the actual count can range from seven to twelve, with eight to twelve being typical. Nine is simply the statistical average observed in many populations.
How does this fish breathe in low oxygen water?
As a physoclist, it cannot gulp air from the surface like some other fish. Instead, it uses aquatic surface respiration. This involves rising to the top millimetre of water, where dissolved oxygen levels are highest, to ventilate its gills effectively during hypoxic conditions.
What is the difference between this and the three-spined stickleback?
The ninespine has a more elongated body and a thinner tail stalk. It lacks scales but has bony plates near the tail. The key identifier is the number of spines before the dorsal fin, which is usually higher than three. It also relies more on vegetation for cover.
Good reading and sources
- Ninespine stickleback on WikipediaEncyclopedia
- More photos on Wikimedia CommonsPhotos
- Wikidata recordOpen data
The facts on this page come from the Wikipedia article "Ninespine stickleback", written by its contributors and used under the CC BY-SA 4.0 licence, and from its Wikidata record (CC0). EveryFish rewrote the text in its own words, with AI assistance, and compares every page with the article to make sure no passage is copied. It may be reused under the same CC BY-SA 4.0 licence with a link back.
It may contain mistakes, and figures change over time. Nothing here is investment or buying advice. If something is wrong, tell us. Last refreshed 2026-11-15.
Like Ninespine stickleback
All other fish
WorldThree-spined stickleback
Small northern fish known for rapid evolution and complex breeding.Other · Rivers and lakes
🇺🇸 United States and 1 moreMexican tetra
A freshwater characin with surface and blind cave forms, studied for evolutionary biology.Other · Rivers and lakes
🇨🇺 CubaCuban gar
Large tropical freshwater predator native to western Cuba.Other · Rivers and lakes
🇦🇷 Argentina and 4 moreArgentinian silverside
A large, adaptable silverside native to South America.Other · Rivers and lakes