Bighead Carp, Hypophthalmichthys nobilis
Bighead Carp, Hypophthalmichthys nobilis. Fish caught in the Cache River, Illinois, April 2013. Length: 1.01 m (3 feet 4 inches). Catch, photograph, and identification courtesy of Ben Cantrell, Madison, Wisconsin.
Bighead Carp, Hypophthalmichthys nobilis. Fish caught in the Cache River, Illinois, April 2013. Length: 1.03 m (3 feet 6 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).
The Bighead Carp, Hypophthalmichthys nobilis, is a member of the Carp and Minnow or Cyprinidae Family, and is known in Mexico as carpa cabezona. Globally, there are only three species in the Hypophthalmichthys genus, of which two are farmed in Mexico and also found in most freshwater systems in Mexico. They quickly escaped captivity and today are considered a highly invasive species that is causing major destruction of habitat. Pound for pound they are the number five species produced globally via aquaculture at a level of 5,000,000 tons per year and represent a $3 billion global market. They are currently present in more than twenty countries.
The Bighead Carp has a laterally compressed body with a depth that is 28% to 32% of standard length with a round abdomen. They are dark gray in color transitioning to cream ventrally with dark gray to black irregular blotches on the back and sides. They have a large head with a terminal mouth slanting upwards with one row of pharyngeal teeth on each side and a protruding lower jaw. Their eyes are found low and forward on the head. Their anal fin has 1 to 3 spines and 12 to 14 rays; their dorsal fin has 3 spines and 7 rays; the pectoral fins have 1 spine and 17 rays; and, their pelvic fins have 1 spine and 8 rays and reach past the anus. They have more than 400 large dense, long, comb-like, close set gill rakers that are utilized to strain planktonic organisms from water. They are covered with small, flat scales. Their lateral line extends to the caudal peduncle.
The Bighead Carp inhabit lakes, rivers and reservoirs and are found in the upper layer of the water column. They prefer high fertility water with abundant natural food. They are a eurythermic fish capable of surviving in water temperatures between 1oC (34oF) and 38oC (100oF) and also waters with some salinity. They reside at depths during the day and move at night to shallow waters for foraging. They reach a maximum of 1.46 m (4 feet 9 inches) in length and 41 kg (90 lbs) in weight. As of January 1, 2023, the International Game Fish Association world record stood at 40.8 kg (90 lbs 0 oz) in weight, with the fish caught in in a lake in Tennessee in 2005. They are bottom filter feeders that primarily consume phytoplankton, zooplankton, small invertebrates and detritus. They lack a stomach and feed continuously. Reproduction occurs once a year in large turbulent rivers and involves a long migratory run with external fertilization, the released eggs being quickly fertilized by males. Each female can release up to 1,600,000 eggs per year. The eggs hatch within sixty hours The eggs either reside on the bottom or float mid-water, thus requiring a water flow to remain suspended. They hatch in 40 to 60 hours. They have been known to hybridize with the Silver Carp, Hypophthalmichthys molitrix. They have lifespans of twenty years.
The Bighead Carp has been farmed for more than a thousand years. Bighead carp ranks 5th among all cultured freshwater fish globally. They have fast growth rates and survive drastic changes in water conditions and can be raised with limited labor and for very low costs. They can be brought to market in eight to ten months and are marketed fresh as whole fish or cut into pieces.
The Bighead Carp was introduced to Mexico in 1975 with fish brought in from Cuba with the intention that they be raised by aquaculture to provide a low cost source of food for the local people. They have since escaped and can now be found in the majority of Mexico’s freshwater systems.
The Bighead Carp is similar to and can be confused with the Silver Carp, Hypophthalmichthys molitrix (silvery bronze head, uniform silvery sides).
From a conservation perspective the Bighead Carp is currently considered Data Deficient. They are known to very quickly become highly invasive and can take over large bodies of water. They are marketed fresh and frozen but are not an esteemed food fish. Their heads are the most popular component and utilized in soup. The sale of the more popular live fish is heavily regulated, and their importation and possession has been banned in certain areas. Smaller fish have numerous bones. They are difficult to catch via hook and line as they are filter feeders and are popular targets of bowfishermen. They are utilized to remove excess or undesirable plankton and thus improve water quality in sewage treatment plants and aquaculture facilities.