Sacramento Blackfish
Encyclopedia
The Sacramento blackfish, Orthodon microlepidotus, is a cyprinid
fish
of central California
. It is the sole member of its genus.
Blackfish are distinctive for their overall dark color (thus the common name). Younger individuals are more silvery, but darken as they age. The scales are unusually small, counting 90-114 along the lateral line
. The forehead has a straight-line profile, the eyes are smallish, and the terminal mouth slants upwards. The dorsal fin starts just behind the pelvic fins, and has 9-11 rays, while the anal fin has 8-9 rays, and the pelvic fins 10 rays. The pharyngeal teeth
are long, straight, and knife-shaped; the dorsal part of each tooth has a narrow grinding surface. They have been recorded at up to 55 cm in length.
Unlike most North American cyprinids, they feed on zooplankton
, planktonic algae, and floating detritus, including rotifer
s, copepod
s, cladocera
ns, diatom
s, and the like. Younger fish pick at food items individually, while adults work by pumping large amounts of water through the oral cavity; the food bits are caught in a patch of mucus on the roof of the mouth, where it is secreted by a special organ, and then the fish swallows mucus and food together.
Blackfish are primarily denizens of the warm turbid waters found on the floor of the Central Valley, such as sloughs and oxbow lake
s connected to the Sacramento
and San Joaquin River
s. They are also common in Clear Lake, Pajaro River
, Salinas River
, the small creeks that feed into San Francisco Bay
. A population is present in the Russian River
, although they may have been introduced. They also thrive in reservoirs, and have been spread to a number of California reservoirs via the California Aqueduct
, and into Nevada via the Lahontan Reservoir (1964) where they have further colonized the Humboldt River
drainage.
Sacramento blackfish are of some commercial significance, and are sold live at many Asian fish markets in California.
Cyprinid
The family Cyprinidae, from the Ancient Greek kyprînos , consists of the carps, the true minnows, and their relatives . Commonly called the carp family or the minnow family, its members are also known as cyprinids...
fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
of central California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
. It is the sole member of its genus.
Blackfish are distinctive for their overall dark color (thus the common name). Younger individuals are more silvery, but darken as they age. The scales are unusually small, counting 90-114 along 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...
. The forehead has a straight-line profile, the eyes are smallish, and the terminal mouth slants upwards. The dorsal fin starts just behind the pelvic fins, and has 9-11 rays, while the anal fin has 8-9 rays, and the pelvic fins 10 rays. The 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...
are long, straight, and knife-shaped; the dorsal part of each tooth has a narrow grinding surface. They have been recorded at up to 55 cm in length.
Unlike most North American cyprinids, they feed on zooplankton
Zooplankton
Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...
, planktonic algae, and floating detritus, including rotifer
Rotifer
The rotifers make up a phylum of microscopic and near-microscopic pseudocoelomate animals. They were first described by Rev. John Harris in 1696, and other forms were described by Anton van Leeuwenhoek in 1703...
s, copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s, cladocera
Cladocera
Cladocera is an order of small crustaceans commonly called water fleas. Around 620 species have been recognised so far, with many more undescribed. They are ubiquitous in inland aquatic habitats, but rare in the oceans. Most are long, with a down-turned head, and a carapace covering the apparently...
ns, diatom
Diatom
Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...
s, and the like. Younger fish pick at food items individually, while adults work by pumping large amounts of water through the oral cavity; the food bits are caught in a patch of mucus on the roof of the mouth, where it is secreted by a special organ, and then the fish swallows mucus and food together.
Blackfish are primarily denizens of the warm turbid waters found on the floor of the Central Valley, such as sloughs and oxbow lake
Oxbow lake
An oxbow lake is a U-shaped body of water formed when a wide meander from the main stem of a river is cut off to create a lake. This landform is called an oxbow lake for the distinctive curved shape, named after part of a yoke for oxen. In Australia, an oxbow lake is called a billabong, derived...
s connected to the Sacramento
Sacramento River
The Sacramento River is an important watercourse of Northern and Central California in the United States. The largest river in California, it rises on the eastern slopes of the Klamath Mountains, and after a journey south of over , empties into Suisun Bay, an arm of the San Francisco Bay, and...
and San Joaquin River
San Joaquin River
The San Joaquin River is the largest river of Central California in the United States. At over long, the river starts in the high Sierra Nevada, and flows through a rich agricultural region known as the San Joaquin Valley before reaching Suisun Bay, San Francisco Bay, and the Pacific Ocean...
s. They are also common in Clear Lake, Pajaro River
Pajaro River
The Pajaro River is a river in Northern California, forming part of the border between Santa Cruz County and Monterey County and between San Benito County and Santa Clara County.-History:...
, Salinas River
Salinas River (California)
The Salinas River is the largest river of the central coast of California, running and draining 4,160 square miles. It flows north-northwest and drains the Salinas Valley that slices through the Coast Range south from Monterey Bay...
, the small creeks that feed into San Francisco Bay
San Francisco Bay
San Francisco Bay is a shallow, productive estuary through which water draining from approximately forty percent of California, flowing in the Sacramento and San Joaquin rivers from the Sierra Nevada mountains, enters the Pacific Ocean...
. A population is present in the Russian River
Russian River (California)
The Russian River, a southward-flowing river, drains of Sonoma and Mendocino counties in Northern California. With an annual average discharge of approximately , it is the second largest river flowing through the nine county Greater San Francisco Bay Area with a mainstem 110 miles ...
, although they may have been introduced. They also thrive in reservoirs, and have been spread to a number of California reservoirs via the California Aqueduct
California Aqueduct
The Governor Edmund G. Brown California Aqueduct is a system of canals, tunnels, and pipelines that conveys water collected from the Sierra Nevada Mountains and valleys of Northern- and Central California to Southern California. The Department of Water Resources operates and maintains the...
, and into Nevada via the Lahontan Reservoir (1964) where they have further colonized the Humboldt River
Humboldt River
The Humboldt River runs through northern Nevada in the western United States. At approximately long it is the second longest river in the Great Basin, after the Bear River. It has no outlet to the ocean, but instead empties into the Humboldt Sink...
drainage.
Sacramento blackfish are of some commercial significance, and are sold live at many Asian fish markets in California.