Totoaba
Encyclopedia
The totoaba or totuava (Totoaba macdonaldi) is a marine
fish
of the drum family (Sciaenidae
) that is indigenous to the northern half of the Gulf of California
in Mexico
. Formerly abundant and subject to an intensive fishery
, the totoaba has become rare, and is listed on CITES, the IUCN Red List of Threatened Species
, and the Endangered Species Act
(ESA).
The totoaba can grow up to two metres in length and 100 kg
in weight. Their diet consists of finned fish
and crustacean
s. While individuals may live up to fifteen years, sexual maturity is usually not reached until the fish are six or seven years old. As totoaba spawn
only once a year, population growth is slow, with a minimum population doubling time
of four-and-a-half to fifteen years. The totoaba spawn in the Colorado River
delta
, which also serves as a nursery for the young fish. The diversion of water from the Colorado River within the United States
leaves little or no fresh water to reach the delta, greatly altering the environment in the delta, and the salinity of the upper Sea of Cortez. The flow of fresh water to the mouth of the Colorado since the completion of the Hoover
and Glen Canyon
dams has been only about 4% of the average flow during the period from 1910 to 1920. This is considered to be a major cause of the depletion of the totoaba population.
The totoaba population is found in two distinct groups. Larval and juvenile stages occupy the Colorado delta, while the adult breeding population lives for most of the year in deeper water towards the middle of the Sea of Cortez. The adult population migrates to the Colorado delta in April and May to spawn. One-year old totoaba are metabolically most efficient in brackish water
of about 20 ppt (parts per thousand) salinity
, a level that occurred naturally in the delta before the diversion of water from the river that occurred in the middle of the 20th century. with the loss of the fresh water flow from the river, salinity in the delta is usually 35 ppt or higher.
Commercial fishing for totoaba began in the 1920s. The catch reached 2,000 metric tons in 1943, but had fallen to only 50 tons in 1975, when Mexico protected the totoaba and banned the fishery. Anectodal evidence suggests that totoaba were very abundant prior to the start of the commercial fishery, but there is no hard evidence of natural population size. Recent studies indicate that the totoaba population has stabilized at a low level, perhaps a bit bigger than when the commercial fishery was banned in 1975. Totoaba are still caught, as by-catch
in fishing for other finned fish and for shrimp, and in illegal fishing for totoaba directly. Some totoaba are illegally exported to the United States
, often misidentified as white seabass
. The government of Baja California has authorized commercial raising of totoaba in fish farms
.
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
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 the drum family (Sciaenidae
Sciaenidae
Sciaenidae is a family of fish commonly called drums, croakers, or hardheads for the repetitive throbbing or drumming sounds they make...
) that is indigenous to the northern half of the Gulf of California
Gulf of California
The Gulf of California is a body of water that separates the Baja California Peninsula from the Mexican mainland...
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...
. Formerly abundant and subject to an intensive fishery
Fishery
Generally, a fishery is an entity engaged in raising or harvesting fish which is determined by some authority to be a fishery. According to the FAO, a fishery is typically defined in terms of the "people involved, species or type of fish, area of water or seabed, method of fishing, class of boats,...
, the totoaba has become rare, and is listed on CITES, the IUCN Red List of Threatened Species
IUCN Red List
The IUCN Red List of Threatened Species , founded in 1963, is the world's most comprehensive inventory of the global conservation status of biological species. The International Union for Conservation of Nature is the world's main authority on the conservation status of species...
, and the Endangered Species Act
Endangered Species Act
The Endangered Species Act of 1973 is one of the dozens of United States environmental laws passed in the 1970s. Signed into law by President Richard Nixon on December 28, 1973, it was designed to protect critically imperiled species from extinction as a "consequence of economic growth and...
(ESA).
The totoaba can grow up to two metres in length and 100 kg
Kilogram
The kilogram or kilogramme , also known as the kilo, is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype Kilogram , which is almost exactly equal to the mass of one liter of water...
in weight. Their diet consists of finned fish
Actinopterygii
The Actinopterygii or ray-finned fishes constitute a class or sub-class of the bony fishes.The ray-finned fishes are so called because they possess lepidotrichia or "fin rays", their fins being webs of skin supported by bony or horny spines , as opposed to the fleshy, lobed fins that characterize...
and crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s. While individuals may live up to fifteen years, sexual maturity is usually not reached until the fish are six or seven years old. As totoaba spawn
Spawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...
only once a year, population growth is slow, with a minimum population doubling time
Doubling time
The doubling time is the period of time required for a quantity to double in size or value. It is applied to population growth, inflation, resource extraction, consumption of goods, compound interest, the volume of malignant tumours, and many other things which tend to grow over time...
of four-and-a-half to fifteen years. The totoaba spawn in the Colorado River
Colorado River
The Colorado River , is a river in the Southwestern United States and northwestern Mexico, approximately long, draining a part of the arid regions on the western slope of the Rocky Mountains. The watershed of the Colorado River covers in parts of seven U.S. states and two Mexican states...
delta
River delta
A delta is a landform that is formed at the mouth of a river where that river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or another river. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river...
, which also serves as a nursery for the young fish. The diversion of water from the Colorado River within the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
leaves little or no fresh water to reach the delta, greatly altering the environment in the delta, and the salinity of the upper Sea of Cortez. The flow of fresh water to the mouth of the Colorado since the completion of the Hoover
Hoover Dam
Hoover Dam, once known as Boulder Dam, is a concrete arch-gravity dam in the Black Canyon of the Colorado River, on the border between the US states of Arizona and Nevada. It was constructed between 1931 and 1936 during the Great Depression and was dedicated on September 30, 1935, by President...
and Glen Canyon
Glen Canyon Dam
Glen Canyon Dam is a concrete arch dam on the Colorado River in northern Arizona in the United States, just north of Page. The dam was built to provide hydroelectricity and flow regulation from the upper Colorado River Basin to the lower. Its reservoir is called Lake Powell, and is the second...
dams has been only about 4% of the average flow during the period from 1910 to 1920. This is considered to be a major cause of the depletion of the totoaba population.
The totoaba population is found in two distinct groups. Larval and juvenile stages occupy the Colorado delta, while the adult breeding population lives for most of the year in deeper water towards the middle of the Sea of Cortez. The adult population migrates to the Colorado delta in April and May to spawn. One-year old totoaba are metabolically most efficient in brackish water
Brackish water
Brackish water is water that has more salinity than fresh water, but not as much as seawater. It may result from mixing of seawater with fresh water, as in estuaries, or it may occur in brackish fossil aquifers. The word comes from the Middle Dutch root "brak," meaning "salty"...
of about 20 ppt (parts per thousand) salinity
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
, a level that occurred naturally in the delta before the diversion of water from the river that occurred in the middle of the 20th century. with the loss of the fresh water flow from the river, salinity in the delta is usually 35 ppt or higher.
Commercial fishing for totoaba began in the 1920s. The catch reached 2,000 metric tons in 1943, but had fallen to only 50 tons in 1975, when Mexico protected the totoaba and banned the fishery. Anectodal evidence suggests that totoaba were very abundant prior to the start of the commercial fishery, but there is no hard evidence of natural population size. Recent studies indicate that the totoaba population has stabilized at a low level, perhaps a bit bigger than when the commercial fishery was banned in 1975. Totoaba are still caught, as by-catch
By-catch
The term “bycatch” is usually used for fish caught unintentionally in a fishery while intending to catch other fish. It may however also indicate untargeted catch in other forms of animal harvesting or collecting...
in fishing for other finned fish and for shrimp, and in illegal fishing for totoaba directly. Some totoaba are illegally exported to the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, often misidentified as white seabass
White seabass
White seabass or white weakfish, Atractoscion nobilis, is a species of croaker occurring from Magdalena Bay, Baja California, to Juneau, Alaska. They usually travel in schools over deep rocky bottoms and in and out of kelp beds....
. The government of Baja California has authorized commercial raising of totoaba in fish farms
Fish farming
Fish farming is the principal form of aquaculture, while other methods may fall under mariculture. Fish farming involves raising fish commercially in tanks or enclosures, usually for food. A facility that releases young fish into the wild for recreational fishing or to supplement a species'...
.
External links
- Mexfish.com Totoaba - Retrieved July 11, 2007
- Long live the totoaba - Retrieved July 11, 2007
- History of the Totoaba - Retrieved July 11, 2007