Silver Carp

Silver Carp, Hypophthalmichthys molitrix

Silver Carp, Hypophthalmichthys molitrix, Juvenile. Fish caught in Apple Creek, Old Appleton, Missouri, July 2019. Length: 7.2 cm (2.8 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.

Silver Carp, Hypophthalmichthys molitrix. Fish caught in the Kaskaskia River, Evansville, Illinois, June 2016. Length: 51 cm (20 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).

Silver Carp, Hypophthalmichthys molitrix. Fish caught in the Kaskaskia River, Illinois, June 2016. Length: 86 cm (2 feet 10 inches). Catch, photograph, and identification courtesy of Ben Cantrell, Peoria, Illinois.

The Silver Carp, Hypophthalmichthys molitrix, is a member of the Carp and Minnow or Cyprinidae Family,  that is also known as the Flying Carp (with good reason!) and in Mexico as carpa plateada. Globally, there are only three species in the genus Hypophthalmichthys, two of which are farmed in Mexico and also found in most freshwater systems in Mexico. The Silver Carp dates to the Chinese Tang Dynasty, 7th to 10th century, and was imported to North America in the 1970s to control algae growth in reservoirs and municipal waste water treatment facilities and for aquaculture. 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 one species produced globally via aquaculture. They are currently present in eighty-eight countries.

The Silver Carp has an elongated and laterally compressed body that is widest near the origin of the dorsal fin. Younger fish are silvery in color; as they age, they fade to olive-green dorsally and silvery ventrally. Their fins are dusky with the caudal fin being darker than the others. Their large head has a large terminal mouth, small eyes found far forward on the mid-line of the body, and an overhanging front jaw. Their mouth extends to the margin of the eyes. Their anal fin has 13 to 15 rays; their caudal fin is forked; and their dorsal fin has 8 rays and originates posterior to the pelvic fin base. They have a ventral keel that extends from the isthmus to the anus. Their body is covered with small scales.

The Silver Carp is a deep-bodied freshwater fish found in backwater areas of large streams, rivers, and water reservoirs with dense aquatic vegetation. As of January 1, 2023, the International Game Fish Association world record stood at 1.3 m (4 feet 3 inches) in length and 48.5 kg (106 lbs 10 oz) in weight, with the fish caught in German Waters in 2003. They are filter feeders, consuming phytoplankton, zooplankton, and detritus. They significantly increase the turbidity of the water body in which they reside by their bottom feeding. They are found in temperate waters with temperatures between 6oC (43oF) and 28oC (82oF) and can tolerate salinities up to 12 ppt and low dissolved oxygen. Reproduction involves external fertilization with released eggs being quickly fertilized by males. Each female can release up to 5,000,000 eggs per year. After hatching, the eggs either reside on the bottom or float mid-water, thus requiring a water flow to remain suspended. They are non-migratory and have a lifespan of up to twenty years.

In Mexico, the Silver Carp is second to the Common Carp as a farmed carp, with explosive growths in production occurring over the last 10 years. They currently have a wide distribution and are farmed in the states of Aguascalientes, Chiapas, Chihuahua, Coahuila, Durango, Guanajuato, Hidalgo, Jalisco, Mexico, Michoacán, Oaxaca, Puebla, Querétaro, San Luis Potosí, Sonora, Tlaxcala, and Zacatecas. The farming of Silver Carps is more economical than with other carp as they do not require expensive formulated feed, are environmentally friendly, and provide a low-priced source of animal protein. Global production levels are currently at 10,000,000 million tons per annum and doubling every ten years. Also seeds are readily available from artificial breeding, without reliance on natural resources. They grow and mature faster than other carp but require a great deal of space and plentiful food sources to survive. The majority of current research on this species focuses on integrated farming in small-scale aquaculture in developing countries.

The Silver Carp received its alternative common name Flying Carp due to its tendency to go airborne when startled. It is capable of leaping 10 feet into the air – see for example – https://www.youtube.com/watch?v=YtFJ7IvQ-dE!). They have also been featured in an episode of River Monsters.

The Silver Carp is similar to and can be confused with the Bighead Carp, Hypophthalmichthys nobilis (dark head, dark mottling on the body).

From a conservation perspective the Silver Carp is currently considered to be of Least Concern with stable widely distributed populations. They are highly invasive and currently present in twelve states of the mid-western United States. Millions of dollars are currently being spent to try to keep them from entering the Great Lakes systems via the Chicago Sanitary and Ship Canal. One concern is that they are transported and introduced to new water systems by fishermen who use them as live bait. The importation of live fish and/or their use as live bait is currently banned in several states in the United States. There is a major ongoing effort to remove all wild Silver Carp from the United States. They are utilized on a limited basis with marginal results for controlling noxious blue-green algae (cyanobacteria) in numerous water bodies. As a result, they are in direct competition with all native species that depend on zooplankton for survival including the Bigmouth Buffalo, the Gizzard Shad, and the Paddlefish. They are very difficult to catch via hook and line because of their dietary habits. The most effective way to catch them is via a “suspension method”, consisting of a large dough ball that disintegrates slowly, surrounded by a nest of tiny hooks that are embedded in the bait. The entire apparatus is suspended below a large bobber. The fish feed on the small particles released from the dough ball and will bump against it with the intention of breaking off more small particles that can be filtered from the water, eventually becoming hooked on the tiny hooks. They are also caught by bow fishermen via “snagging” with large weighted treble hooks, either while in the water or when airborne, or simply by catching flying fish from boats with nets. They are marketed alive and fresh close to where they are raised and are generally the lowest priced fish in the market. There is virtually no export market from Mexico established for this species. Some of the larger Silver Carp contain algal toxins built up in their systems making them hazardous to eat.