The Sacramento blackfish (''Orthodon microlepidotus'') is a species of
freshwater fish
Freshwater fish are those that spend some or all of their lives in fresh water, such as rivers and lakes, with a salinity of less than 1.05%. These environments differ from marine conditions in many ways, especially the difference in levels of s ...
in central
California
California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
. A
cyprinid
Cyprinidae is a family of freshwater fish commonly called the carp or minnow family. It includes the carps, the true minnows, and relatives like the barbs and barbels. Cyprinidae is the largest and most diverse fish family and the largest verte ...
, the blackfish is the sole member of its genus.
Distribution and habitat
Blackfish are primarily denizens of the warm and cloudy waters found on the floor of the Central Valley, such as sloughs and
oxbow lake
An oxbow lake is a U-shaped lake or pool that forms when a wide meander of a river is cut off, creating a free-standing body of water. In South Texas, oxbows left by the Rio Grande are called '' resacas''. In Australia, oxbow lakes are call ...
s connected to the
Sacramento
)
, image_map = Sacramento County California Incorporated and Unincorporated areas Sacramento Highlighted.svg
, mapsize = 250x200px
, map_caption = Location within Sacramento ...
and
San Joaquin River
The San Joaquin River (; es, Río San Joaquín) is the longest river of Central California. The long river starts in the high Sierra Nevada, and flows through the rich agricultural region of the northern San Joaquin Valley before reaching Suis ...
Pajaro River
The Pajaro River (''pájaro'' is ''bird'' in Spanish language, Spanish) is a U.S. river in the Central Coast (California), Central Coast region of California, forming part of the border between San Benito County, California, San Benito and Santa ...
San Francisco Bay
San Francisco Bay is a large tidal estuary in the U.S. state of California, and gives its name to the San Francisco Bay Area. It is dominated by the big cities of San Francisco, San Jose, and Oakland.
San Francisco Bay drains water from a ...
. A population is present in the Russian River, believed to have been introduced. They also thrive in reservoirs, and have been spread to a number of California reservoirs via the
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. Named after Cali ...
, and into Nevada via the
Lahontan Reservoir
Modern Lake Lahontan is a reservoir on the Carson River in northwest Nevada in the United States. It is formed by the Lahontan Dam, built in 1905 by the Bureau of Reclamation as part of the Newlands Reclamation Act and is located between Fallon, ...
(1964) where they have further colonized the
Humboldt River
The Humboldt River is an extensive river drainage system located in north-central Nevada. It extends in a general east-to-west direction from its headwaters in the Jarbidge, Independence, and Ruby Mountains in Elko County, to its terminus in the ...
drainage.Peter B. Moyle, ''Inland Fishes of California'' (University of California Press, 2002), pp. 144–146
Description
Anatomy and morphology
Blackfish are named for their glossy black color. Younger individuals are more silvery, but darken as they age. The scales are unusually small, counting 90-114 along the
lateral line
The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...
. The forehead has a straight-line profile, the eyes are small, and the terminal mouth slants upwards. The
dorsal fin
A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...
starts just behind the
pelvic fin
Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods.
Structure and function Structure
In actinopterygians, the pelvic fin consists of two en ...
s, and has 9-11
rays
Ray may refer to:
Fish
* Ray (fish), any cartilaginous fish of the superorder Batoidea
* Ray (fish fin anatomy), a bony or horny spine on a fin
Science and mathematics
* Ray (geometry), half of a line proceeding from an initial point
* Ray (gra ...
, while the anal fin has 8-9 rays, and the pelvic fins 10 rays. The
pharyngeal teeth
Pharyngeal teeth are teeth in the pharyngeal arch of the throat of cyprinids, suckers, and a number of other fish species otherwise lacking teeth.
Behavior and diet
Unlike most North American
cyprinids
Cyprinidae is a family of freshwater fish commonly called the carp or minnow family. It includes the carps, the true minnows, and relatives like the barbs and barbels. Cyprinidae is the largest and most diverse fish family and the largest vert ...
, Sacramento blackfish
filter feed
Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...
on
zooplankton
Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...
, planktonic algae, and floating detritus, including
rotifer
The rotifers (, from the Latin , "wheel", and , "bearing"), commonly called wheel animals or wheel animalcules, make up a phylum (Rotifera ) of microscopic and near-microscopic pseudocoelomate animals.
They were first described by Rev. John H ...
s,
copepod
Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...
s,
cladocera
The Diplostraca or Cladocera, commonly known as water fleas, are a superorder of small crustaceans that feed on microscopic chunks of organic matter (excluding some predatory forms).
Over 1000 species have been recognised so far, with many more ...
ns,
diatom
A diatom (Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising sev ...
s, and the like. While younger blackfish pick at food items individually, adults primarily use the oral cavity and
gill
A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...
s to filter food from water. The blackfish opens and closes its mouth rapidly to pump large volumes of water, the food bits are caught in a patch of mucus on the roof of the mouth, where it is secreted by the palatal organ, and the food bits are swallowed with the mucus. The size of a blackfish influences its eating behavior; larger blackfish, with subsequently larger oral cavities and easier means of filter feeding, are not seen pursuing individual prey like shorter blackfish.
Life cycle
Sacramento blackfish usually live no more than five years. Most blackfish quickly grow during their first and second years, maturing at 2–3 years of age. The blackfishes' breeding season occurs from the spring through early summer, where males will fertilize female eggs in shallow waters. Due to physical stresses from reproduction, many blackfish find
spawning
Spawn is the eggs and sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of releasing the eggs and sperm, and the act of both sexes is called spawning. Most aquatic animals, except for aquati ...
difficult and die after two seasons, but some can reproduce up to four times.
Taxonomy
''Orthodon microlepidotus,'' the common name for the Sacramento blackfish, refers to the fish's straight teeth (Orthodon) and its distinctly small scales (microlepidotus). The Orthodon genus is monotypical, making the blackfish the sole member of the genus and a generally unvaried species. Despite its unique characteristics, the blackfish has been recorded reproducing hybrids with the Hitch and Tui Chubs, members of the blackfish's subfamily
Leuciscinae
Leuciscinae is a subfamily of the freshwater fish family Cyprinidae, which contains the true minnows.
Members of the Old World (OW) clade of minnows within this subfamily are known as European minnows. As the name suggests, most members of the O ...
also found in California.
Status
The IUCN labels the Sacramento blackfish as being of "least concern"—though less abundant than previously in California's Central Valley, the blackfish is at low risk of endangerment. Blackfish are known for their adaptations to environmental extremes, especially adapting to fluctuating water temperatures. A study by Joseph J. Cech Jr., a professor at the
University of California, Davis
The University of California, Davis (UC Davis, UCD, or Davis) is a public land-grant research university near Davis, California. Named a Public Ivy, it is the northernmost of the ten campuses of the University of California system. The institut ...
, found that the blackfish was able to thrive in hypoxic environments.
Sacramento blackfish are of some commercial significance, and are sold live at many Asian fish markets in California.They are also seen as a potential
aquaculture
Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. lot ...