Overview
The Brook Stickleback (Culaea inconstans) is a fascinating, small freshwater fish famous for the sharp, isolated dorsal spines lining its back and the intricate bird-like nests constructed by breeding males. Inhabiting the quiet, weed-choked brooks and cold springs of the northern wilderness, this resilient minnow-sized fish is a master architect that binds aquatic mosses together with a specialized biological glue produced by its own kidneys.
Biology and Physical Characteristics
Culaea inconstans features a slender, laterally compressed scaleless body covered in smooth skin, colored mottled olive-green to dark brown with a pale yellowish underside. Along its back, it carries 4 to 6 (most commonly 5) sharp, erect dorsal spines that can be locked into an upright position by specialized pelvic bones, discouraging larger predatory trout and bass from swallowing it.
Behavior and Ecology
In spring, the male Brook Stickleback transforms into a striking velvety jet-black with vibrant scarlet highlights. He weaves a tubular, hollow nest out of green algae, moss, and waterweeds, gluing the plant fibers securely to aquatic stems using a sticky protein thread called ‘spiggin’ secreted by his kidneys. He then courts females through elaborate dances, leading them inside to lay eggs, which he aggressively aerates and protects.
Conservation and Human Impact
Assessed as Least Concern by the IUCN, the Brook Stickleback is exceptionally abundant throughout northern boreal watersheds. Its high tolerance for cold, low-oxygen waters allows it to survive in shallow, winterkill-prone northern wetlands where larger predatory fish cannot survive.
Interesting Factoid
Male Brook Sticklebacks build hollow, tubular underwater homes out of moss and algae, using a biological superglue called ‘spiggin’ produced by their own kidneys to glue the nest securely to submerged weeds.