The Brook Stickleback has a bit of a punk rock vibe to it. Although quite small, its five pointy dorsal spines make it look like it just came out of London, U.K. circa 1977.
They are quite populous in the northern parts of the United States and much of Canada. In Canada, their most prolific habitats are Arctic and Atlantic drainages (rivers and lakes) from Nova Scotia through to the Northwest Territories and Nunavut, as well as the Great Lakes/Mississippi basin from Ohio to New Brunswick and west into Montana and the eastern parts of British Columbia.
These habitats are preferred because Brook Sticklebacks like the shallows near the shorelines of very clear lakes and ponds - the more vegetation cover the better. They also like cool creeks and small rivers as long as the current is not too strong and if the riverbed is sandy, graveled or muddy. Temperatures between 4 C and 18 C are ideal, trending towards the cooler end of that spectrum.
At their biggest, Brook Sticklebacks rarely exceed 6 cm in length, making them about the size of larger minnows, which are their main competitors for food and breeding grounds, although the competition is pretty tame, since each species prefers to feed and breed at different times of day.
In terms of what it likes to eat, the diet of the Brook Stickleback is quite varied, with a preference for the larvae of aquatic insects, small land-borne insects, crustaceans, eggs of other fish species and their larvae, snails, earthworms, and smaller parasitic worms (nematodes) and mites. At times, when necessary, they will also indulge in a vegetarian option, such as algae or plants with vascular systems (roots, branches etc.).
As a form of food itself, the Brook Stickleback is on the menu for many different types of invertebrates, birds, mammals and larger fish species. This is why they have adapted to include the spines on their back to discourage being snacked upon, and they have also become quite stealthy and quick to manoeuvre out of harm’s way when under attack. There is a greater issue with their eggs being eaten, including opportunistic cannibalization by other Brook Sticklebacks.
When it’s time for mating, males begin to establish a territory while also building a nest on a vertical plant or stick, making it out of algae, dead plant material and really small twigs. At the same time, they change colour from their normal non-mating time olive to a very dark green - and even black. They then fend off other potential mates through aggressive demonstrations, while also using a method called ‘tail flagging’ to attract females, with ones having a more distinct coloration being preferred.
After fertilization, the male pushes the eggs deep into the nesting material and takes up sentry duty near the entrance. To provide oxygen, he waves his pectoral fins. Hatching happens around 10 days later, with the adult male basically keeping the larvae close to the nest, even running and catching strays in his mouth before returning them to the nesting area. If the escapees become too numerous and difficult to return, he simply eats the ones he catches. No ‘parent of the year’ awards here.
The average lifespan for a surviving larva is about three years in the wild. One advantage they have over their minnow pals is that they are not used as bait by anglers because of their spines. But they are still eaten in significant quantities by so-called sport fishing species like yellow perch, brook trout and smallmouth bass, keeping those populations at high levels. Many Brook Sticklebacks find their way into aquariums but don’t like company, due to their extreme territoriality.
Have you seen one of these interesting species recently?
Sources: Wikipedia, University of Michigan, www.animaldiversity.org, Montana Field Guide.