The brook stickleback gets its name from the row of spines located in front of the dorsal fin. Usually there are five spines, but they may number between two and seven. When removed from the water, the spines lie down and are difficult to see, but they can be counted if you drag your finger backwards from the dorsal fin towards the head. These fish also have an anal fin that is very similar in size to the dorsal fin. A full-grown brook stickleback rarely exceeds 8.5 cm in size.
If you catch a brook stickleback with a net, remember to return it to its home pond. In Alberta it is illegal to transport any live fish taken from public water. This is very important to prevent the spread of exotic species, including its cousin the three-spined stickleback, which has already been illegally introduced to one lake in Alberta.
ADAPTED FOR WINTER SURVIVAL
Beaver ponds support a diverse and productive community of aquatic and wetland plants. Over the winter months, photosynthesis by aquatic plants under the ice slows down and microbes continue to feed upon the abundant dead plant material. Without the mixing with the atmosphere, the dissolved oxygen levels may become too low for other native fish species, especially rainbow trout. The brook stickleback is more tolerant of these conditions.
When the ice melts in the spring, brook sticklebacks provide an important food source for migrating fish-eating birds including loons and grebes. Brook sticklebacks also inhabit other water bodies in the area including nearby Thompson Lake.
Brook sticklebacks are born inside a golf-ball sized nest. The male stickleback makes the nest with pieces of plant material glued to an underwater plant stem with special cement secreted from his kidneys. He lures the female into his nest and convinces her to lay her eggs there – then he takes care
of everything else. For example, he fans a current of water through the nest over the incubating eggs.
After hatching, when the fry (baby fish) stray too far from the nest, the male catches them in his mouth and spits them back into the nest. After a couple of weeks, the young sticklebacks leave the nest to satisfy their appetite for small aquatic
insects, crustaceans and algae.
Did you know?
- The brook stickleback is actually a close relative of the seahorse. It’s small and likes the same habitat but otherwise has little in common with the small fish from the minnow family, such as the pearl dace. Brook sticklebacks have a very distinguished appearance, unique reproductive behaviours, and special adaptations for survival in beaver ponds.