The speckled chub, Macrhybopsis aestivalis, is a species of freshwater fish in the Cyprinidae family of the order Cypriniformes

Cypriniformes

The Cypriniformes are an order of ray-finned fish, including the carps, minnows, loaches and relatives. This order contains 5-6 families, over 320 genera, and more than 3,250 species, with new species being described every few months or so, and new genera being recognized regularly...

, which also includes carp

Carp

Carp are various species of oily freshwater fish of the family Cyprinidae, a very large group of fish native to Europe and Asia. The cypriniformes are traditionally grouped with the Characiformes, Siluriformes and Gymnotiformes to create the superorder Ostariophysi, since these groups have certain...

s, suckers

Catostomidae

Catostomidae is the sucker family of the order Cypriniformes. There are 80 species in this family of freshwater fishes. Catostomidae are found in North America, east central China, and eastern Siberia...

, and loach

Loach

Loach may refer to:* Loaches, fish families in the Cypriniformes:** Cobitidae, the "true" loaches – formerly all loaches were united in this family** Balitoridae, the hillstream loaches – the largest family, closely related to Cobitidae...

es.

Geographic distribution

The speckled chub is native to North America and is mainly found in the United States and Mexico. It is found in the Mississippi River

Mississippi River

The Mississippi River is the largest river system in North America. Flowing entirely in the United States, this river rises in western Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains...

 basin from Minnesota and Nebraska to West Virginia and Ohio, and south to the Gulf Slope drainages from Florida to Texas and New Mexico. It appears to be restricted to large, flowing river channels.

Physical description

Speckled chubs have a slender, compressed body that is usually a yellowish tan to silver in color and may or may not have dark markings present. The underside of the fish is mainly silver. The eyes are situated high on the head, and the lateral line

Lateral line

The lateral line is a sense organ in aquatic organisms , used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...

 consists of 34-41 scales, which can appear either straight or arched. The dorsal fin

Dorsal fin

A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...

 soft rays have faintly dark edges. The mouth is horizontal and inferior, and it has long barbels present at the corners of the mouth. It has a rounded snout with moderately fleshy lips. The lateral line

Lateral line

The lateral line is a sense organ in aquatic organisms , used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...

 is either strait or arched along the length of the body. The speckled chub has less than 10 dorsal fin

Dorsal fin

A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...

 soft rays, 16-21 caudal fin soft rays, 7-9 anal fin soft rays, 6-9 pelvic fin soft rays, and 11-18 pectoral fin soft rays. The speckled chub has pharyngeal teeth

Pharyngeal teeth

Pharyngeal teeth are teeth in the pharyngeal arch of the throat of cyprinids, suckers, and a number of other fish species lacking teeth.Popular aquarium fish such as goldfish and loaches have these structures. Members of the Botia genus such as clown loaches are known to make distinctive clicking...

. The maximum body size is recorded at 7.6 cm, and the average length is 6.1 cm. Speckled chubs rarely live longer than a year and a half.

Habitat and diet

Speckled chubs are found on the bottom of medium to large rivers with moderate to swift currents and sandy or gravelly bottoms. They use the taste buds located on the head, body, and fins to find the aquatic insects they feed on. Generally, they feed on aquatic insect larvae, with a large portion of their diet including the larvae of midges.

Reproduction

Spawning occurs around midday from late April to August, with large aggregations occurring in the lower Pearl River in Mississippi during March and April, and also in the main channels of the Cahaba

Cahaba River

The Cahaba River is the longest free-flowing river in Alabama and is among the most scenic and biologically diverse rivers in the United States. The Cahaba River is a major tributary of the Alabama River and part of the larger Mobile River Basin...

 and Tallapoosa

Tallapoosa River

The Tallapoosa River runs from the southern end of the Appalachian Mountains in Georgia, in the United States, southward and westward into Alabama. It is formed by the confluence of McClendon Creek and Mud Creek in Paulding County, Georgia. Lake Martin at Alexander City, Alabama is a large and...

 Rivers during May and June. These fish have external fertilization

External fertilization

External fertilization is a form of fertilization in which a sperm cell is united with an egg cell external to the bodies of the reproducing individuals. In contrast, internal fertilization takes place inside the female after insemination through copulation....

. Mating is initiated when males pursue a female and nudge her abdomen. When the female is ready to spawn, the male wraps himself around her and the eggs and sperm are released at the same time. This mating behavior is usually repeated with several spawning episodes, generally with at least ten minutes between fertilizations. The speckled chub does not guard its eggs from potential predators.

Conservation status

The speckled chub is considered a threatened species in Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

, however they are quite common in the mainstream Rio Grande River. The speckled chub population has declined in the lower Rio Grande due to reservoir

Reservoir

A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...

s, channelization, and reduced stream flows associated with irrigation.

Etymology of name

The speckled chub is given its name due to the black spots seen on the body. The "macr-" part of its name is a Greek root, meaning "long," which is most likely referring to the long and slender bodies of the genus macrhybopsis minnows. the "aestivalis" part of the name is translated to pertain to summer, which is referring to the long spawning season of the speckled chub.