The brook stickleback (Culaea inconstans) is a small freshwater fish that is distributed across the US and Canada. It grows to a length of about 2 inches. It occupies the northern part of the eastern United States, as well as the southern half of Canada. Small populations are scattered throughout the Mississippi-Great Lakes basin extending to Colorado, New Mexico, Kentucky, Tennessee, etc., though some of these areas are not native to the species. This small fish inhabits clear, cool streams and lakes. They eat small invertebrates, algae, insect larvae, and occasionally their own eggs. They are also preyed upon by smallmouth bass and northern pike. Feeding time is usually dawn and sunset. The brook stickleback does have active competition mostly from minnows, but feeding times are different, along with diet. Spawning occurs in midsummer. Males secure a territory, build a nest, and mate with females. Males provide protection for the eggs, ward off predators, and usually die later in the season. This is considered an annual species. The nests are built out of aquatic grasses. Though the brook stickleback is not considered a threatened species, deforesting and changing waters are altering ecosystems of the species. Harvesting of trees around riparian environments is having a large effect of the stream ecosystem where the brook stickleback resides. Taxonomy The brook stickleback was first formally described as Gasterosteus inconstans in 1840 by the American naturalist Jared Potter Kirtland with its type locality given as Trumbull County, Ohio. In 1876 David Starr Jordan proposed the monospecific genus Eucalia for the brook stickleback but Jordan's name was invalid because it was preoccupied in Lepidoptera. Culaea was then proposed as the replacement name in 1950 by Gilbert Percy Whitley. The brook stickleback is the only species in the genus Culaea which is classified within the stickleback family, Gasterosteidae. Culea is a near anagram of Eucalia which is a combination of eu, meaning "well" and calia, meaning "nested", and allusion to the sticklebacks' building of nests. The specific name incosntans means "variable" and is a reference to the variable number of dorsal spines and fin rays in the dorsal and anal fins. Description The brook stickleback has a tapered body with a slim caudal peduncle and a fan-shaped tail. It very much resembles the ninespine stickleback but only has five, or occasionally six, dorsal spines. It also lacks lateral bony plates. Most of the year the colouring