Culaea Inconstans

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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.Stewart, D.B. 2007.''
Fish diets and food webs in the Northwest Territories: brook stickleback (''Culaea inconstans'').
Canadian Manuscript Report of Fisheries and Aquatic Sciences 2798: 1-17 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.Acere, T.O. 1986. Age, growth and life history of ''Culaea inconstans'' (Pisces: Gasterostidae) in Delta Marsh Lake Manitoba. Hydrobiologia 135: 35-44 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.Chizinski, C. J. 2010. The influence of partial timber harvesting in riparian buffers on macroinvertebrate and fish communities in small streams in Minnesota, USA. Forest Ecology and Management 259: 1946-1958

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 preoccuppied 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 is grayish or olive green with a varying amount of indistinct mottling, but during the spawning season, males are nearly black and females have darker and lighter patches. This species grows to a maximum length of .

Geographic distribution of species

''Culaea inconstans'', commonly known as the brook stickleback, is a small fish (<87 mm) that occurs throughout the southern half of Canada and the northern part of the eastern United States. It is one of the smallest fishes in the region. Brackish water populations are uncommon but certainly exist. It extends down to the southern reaches of the Mississippi River – Great Lakes drainage basins. Populations also exist in Colorado and Nebraska to the west, and in Alberta, Manitoba, and Northwest Territory to the north. Though these are typically the native ranges of the brook stickleback, the species has been introduced to Alabama, Kentucky, Tennessee, northwestern Colorado, northeastern Utah and California, and even in parts of South Dakota and Washington State. Certain geographical distribution studies have found that certain populations may have been native in New Mexico and still exist today. Nebraska does have brook stickleback populations, but they are generally found in small streams in the northern portion of the state. The fish have been found in Nebraska since the early part of the nineteen hundreds. River drainages that sustain brook stickleback populations are the Loup, Middle Platt, Niobrara, and smaller distributions in the Lower Platte, Missouri River tributaries, North Platte, and South Platte. Though the species appears to have an abundant distribution across North America, the Nature Conservancy has declared the species to be a S3 (vulnerable) level. Reasons for the level of vulnerability could be due to increased dam construction, especially in the eastern United States. This can lead to a destruction of habitat, increase in silted waterways, alteration of stream nutrient transport, and damaged breeding grounds. Alteration of stream dynamics could also lead to a change in predator frequency, thus exposing the brook stickleback to unforeseen predators.

Introduction in Europe

The brook stickleback was introduced in upper drainage of the River Inn in Bavaria, and in the 1960s was accidentally introduced to alongside ''Micropterus'' species to Lake Lohjanjarvi in southern Finland and it has become established there''.''

Ecology

As with a large geographical distribution, this species also lives in a wide range of flowing water habitats. Waterways such as rivers, streams, floodwater streams and drainages, lakes, ponds, potholes, hot springs, sinkholes, and seasonal melt water or spring fed ponds are all viable brook stickleback territories. Though the species can thrive in these habitats, primary spawning, breeding, and rearing grounds are located in shallow (< 1.5m) near shore environments with high vegetation cover and low velocity water. The species has a wide elevation range with specimens identified from sea level to ~ 2,400m.

Diet

The brook stickleback is an omnivore, with primary feeding tendencies toward aquatic insect larvae, adult terrestrial insects, crustaceans, fish eggs and larvae, snails, oligochaetes, nematodes, rotifers, and mites. However, brook stickleback feed on vascular plant material, as well as algae. Newly hatched stickleback larvae and planktonic crustaceans from both streams and ponds. Juveniles eat small organisms due to mouth size restrictions, and adults eat both large and small organisms.

Predators

Certain large invertebrates, birds, mammals, and fish all prey on the brook stickleback. With its small size, this species of stickleback has evolved piercing spines and protective plates to hinder predators. With this protection, as well as advanced anti-predator behavior, the brook stickleback is only a minor prey item. In a lab study, adult water bugs (Lethocerus americanus) and dragonfly nymphs (Aeschna spp.) both successfully preyed on the stickleback, but only in a night setting. Fish have been observed to be the most successful predator of the brook stickleback. Examples of these fish predators include yellow perch (Perca flavescens), rock bass (Ambloplites rupestris), creek chub (Semotilus atromaculatus), burbot (Lota lota), central mudminnow ( Umbra limi), smallmouth bass ( Micropterus dolomieu), largemouth bass (Micropterus salmoides), northern pike (Esox lucius), brook trout (Salvelinus fontinalis), rainbow trout (