Silver Carp — This is a species of freshwater fish of the carp family, a species of Asian carp that lives in North and Northeast Asia. It is defined by low-set eyes and an inverted mouth with no antennae. These are fish that prefer to spawn in large rivers with muddy water. They do not unusually migrate long distances, but migrants have been known to travel long distances in desperation.
Species origin and description
Many species belonging to the largest family of cyprinid freshwater fish have been widely represented in many regions of the world — mainly for food and aquaculture — and then avoided becoming harmful invaders, spreading in their new ecosystems and often competing with native species for food and habitat.
Video: Silver carp
Silver carps were raised at six state, federal, and private aquaculture facilities in Arkansas in the 1970s and placed in municipal sewage lagoons. They then escaped to establish themselves in the Mississippi River basin and have since spread through the upper Mississippi River system.
Of all environmental factors, temperature has the greatest effect on silver carp maturity. For example, in the Iranian Terek River, silver carp males mature at 4 years old, and females at 5 years old. About 15% of females mature at 4 years old, but 87% of females and 85% of males are in age groups 5-7.
Interesting fact: The silver carp is known as a species that jumps out of the water when frightened (for example, from the noise of a motor boat).
The average length of the silver carp is about 60-100 cm. But large fish can reach up to 140 cm in body length, and large-sized fish can weigh about 50 kg.
Appearance and features
A silver carp &# 8212; it is a fish with a deep body, laterally compressed. They are silvery in color when young, and as they get older, they change from greenish on their backs to silvery on their belly. They have very small scales on their body, but the head and spines are not scaled.
Silver carps have a large mouth without any teeth in their jaws, but they do have pharyngeal teeth. The teeth of the pharynx are arranged in one row (4-4) and are well developed and compressed with a striated grinding surface. Their eyes are set far forward in the midline of the body and turned slightly downward.
Silver carps are unlikely to be confused with true carp due to their size and unusual eye position. They are most similar to the H. nobilis carp, but have a smaller head and an inverted mouth without teeth, a keel that extends forward past the base of the pelvic fin, lacking the dark spots characteristic of large-headed carp, and branched gill rakes.
Young fish lack spines in their fins. Juveniles are similar to the bighead carp (Hypophthalmichthys nobilis), but their pectoral fin extends only to the base of the pelvic fin (unlike the pelvic fin in the bighead).
Some sources report spines in the dorsal and anal fins silver carp. However, the presented variety of New Zealand lacks thorns.
The silver carp has several fins:
- dorsal fin (9 rays) — small, flag-like;
- anal fin rather long and shallow (15-17 rays);
- caudal fin moderately long and flattened;
- pelvic fins ( 7 or 8 rays) small and triangular;
- pectoral fins (15-18 rays) rather large, returning to insertion of pelvic fins.
In the male silver carp, the inner surface of the pectoral fins, facing the body, is rough to the touch, especially during the breeding season. The intestine is 6-10 times longer than the body. The keels extend from the isthmus to the anus. The total number of vertebrae is 36-40.
The eyes are low on the head with the lower edge below the level of the corner of the mouth, they have a terminal mouth, without antennae. The gills of the silver carp have a complex network and many densely spaced gill rakes. The gill membranes are not connected to the isthmus.
Where does the silver carp live?
The silver carp is found naturally in the temperate waters of China. They inhabit the Yangtze, West River, Pearl River, Kwanxi and Kwangtung river systems in South and Central China and in the Amur basin in Russia. Introduced to the US in the 1970s.
Currently found in:
- South Dakota;
Silver carp — it is primarily a type of large rivers. They can tolerate high salinity and low dissolved oxygen (3 mg/l). In its natural range, the silver carp reaches maturity between 4 and 8 years of age, but has been noted to mature as early as 2 years of age in North America. They can live up to 20 years. This species has been imported and stocked for phytoplankton control in eutrophic waters, and apparently also as a food fish. It was first introduced to the United States in 1973 when a private fish farmer imported silver carp into Arkansas.
By the mid-1970s, the silver carp was bred in six state, federal, and private institutions, and by the late 1970s, it was kept in several municipal sewage lagoons. By 1980, the species was found in natural waters, probably as a result of escaping from hatcheries and other aquaculture facilities.
The appearance of the silver carp in the Ouachita River in the Red River system in Louisiana was likely the result of escape from an aquaculture facility upstream in Arkansas. Introductions of the species in Florida were probably the result of contamination of a stock from which a silver carp was accidentally released, and a stock of carp was used to control aquatic plants.
In a similar case, the species appears to have been accidentally introduced into Lake Arizona as part of a deliberate, albeit illegal, stock of diploid carp. Individuals taken from the Ohio River may have come from stands in local ponds, or entered the Ohio River from populations originally introduced to Arkansas.
Now you know where the silver carp is found. Let's see what this fish eats.
What does a silver carp eat?
The silver carp feeds on both phytoplankton and zooplankton. Silver carps are prolific filter feeders that significantly change both the number of planters and their composition in the community, reducing the amount of food for sport and commercial fish.
Silver carps often swim just below the surface and may travel in large groups (as single species or together). They — great pond reclamators, as they filter detritus from green and dirty water through their mouths. Growing silver carp can prevent the massive occurrence of blue-green algae, the so-called algal bloom, during the summer.
Young fish feed on zooplankton, while adult fish consume nutrient-poor phytoplankton, which they filter into large quantities through the gill apparatus. Because they eat so much algae, they are sometimes referred to as “river cows”. To digest such a large amount of low-calorie food, the silver carp has a very long intestine, 10-13 times longer than its body.
Interesting fact: Silver carp is a very aggressive fish that can consume up to half of its weight in the form of phytoplankton and detritus. They out-compete native fish populations for their aggressive behavior and high consumption of plankton.
Different types of mussels, larvae and adults, such as paddlefish, are most at risk of being out-competed due to for the proven coincidence of the diet with the silver carp.
Peculiarities of character and lifestyle
This species has been introduced to many parts of the world for two reasons: aquaculture and plankton control in nutrient-rich reservoirs and wastewater treatment plants. Their ability to control algal blooms is quite controversial. The silver carp has been reported to be effective in controlling algal blooms if the correct amount of fish is used.
Due to the fact that the silver carp can effectively filter >20 µm algae, hence the amount of small algae increases as a result of lack of fish grazing and increase in nutrients due to internal stress.
Some researchers have suggested the use of silver carp only if the main goal is to reduce the unpleasant blooms of large phytoplankton species, such as cyanobacteria, which cannot be effectively controlled by large herbivorous zooplankton. Silver carp stocks appear to be most suitable in tropical lakes that are highly productive and lack large cladoceral zooplankton.
Others are more inclined to use silver carp not only for algae control, but also for zooplankton and suspended organic matter. They claim that the introduction of 300-450 silver carps into the Netofa Reservoir in Israel has created a balanced ecological system.
Fun fact: Silver carps pose a danger to people due to collisions between fishermen's boats and injury to people jumping into them.
Social structure and reproduction
The silver carp is very prolific. Natural spawning occurs in the upper reaches of fast rivers with a minimum depth of 40 cm and a current speed of 1.3-2.5 m/s. Adults breed in rivers or tributaries above shallow rapids with gravel or sandy bottoms, in the upper water layer, or even on the surface during floods when the water level rises 50-120 cm above normal levels.
Final maturation and spawning of eggs is caused by rising water levels and temperatures. Spawning stops when conditions change (silver carps are especially sensitive to a drop in water level) and resumes when the water level rises. Juveniles and adults form large groups during the spawning season.
Mature individuals make long distance upward migrations at the onset of rapid flooding and rising water levels, and are able to jump over obstacles up to 1 m. After spawning, adults migrate to feeding habitats. In autumn, adults move to deeper places in the main course of the river, where they remain without food. Larvae drift downstream and settle in floodplain lakes, on shallow shores and in swamps with practically no current.
The minimum water temperature for spawning is 18°C. The eggs are pelagic (1.3-1.91 mm in diameter) and increase rapidly in size after fertilization. Egg development and hatching time depend on temperature (60 hours at 18°C, 35 hours at 22-23°C, 24 hours at 28-29°C, 20 hours at 29-30°C).
In winter, the silver carp lives in “winter pits”. They spawn when the water reaches a temperature of 18° to 20° C. The females lay 1 to 3 million eggs, which swell as they develop, migrating passively downstream up to 100 kilometers. Eggs drown and die in stagnant water. The silver carp becomes sexually mature at the age of three to four years. Where it is bred, silver carp — commercially valuable fish.
Natural enemies of silver carp
In their natural habitats, the silver carp population is controlled by natural predators. In the Great Lakes region, there are no native fish species large enough to prey on adult silver carp. White pelicans and eagles feed on young silver carp in the Mississippi basin.
Pelicans found in the western reaches of the Great Lakes and eagles throughout the basin can be expected to do the same. Native predatory fish such as perch may feed on young silver carp. Given its growth rate, many individuals can be expected to grow too large and too fast for predatory fish to exert significant pressure to keep the silver carp population down.
Once populations of silver carp have grown with juvenile recruits in excess of mortality, eradication is considered difficult, if not impossible. Populations can be minimized in some areas by denying access to spawning tributaries through the construction of migration barriers, but this is an expensive proposition and may inadvertently result in negative impacts on native species. Better control of silver carp — it is to prevent them from entering the Great Lakes.
Population and species status
Throughout the course of the Mississippi River, the silver carp population spreads up and downstream from 23 locks and dams (three on the Arkansas River, seven on the Illinois River, eight on the Mississippi River, and five on the Ohio River). There are currently two potential man-made obstacles for silver carp reaching the Great Lakes basin, the first of which is an electrical barrier in the Chicago waterway system that separates the Illinois River from Lake Michigan. This “barrier” is often broken by small and large fish that follow the big boats.
In 2016, an earthen berm 2.3 kilometers long and 2.3 meters high was completed in Eagle Marsh in Fort Wayne, Indiana between the Wabash and Maumee Rivers (the latter leading to Lake Erie). This wetland often experienced flooding and a connection between the two watersheds, and was previously divided by a simple chain link fence through which small fish (and young silver carps) could easily swim. The introduction and breeding of silver carp in the Great Lakes is of great concern to commercial and sport fishers, conservationists and many other interested people.
The silver carp is currently classified as critically endangered in its natural range (as its natural habitat and productive behavior is affected by dam building, overfishing and pollution). But it is readily available in some other countries. The population decline appears to have been particularly significant in the Chinese parts of its range.
The silver carp is a species of Asian carp that is primarily found in Eastern Siberia and China. It is also called the flying carp because of its tendency to jump out of the water when frightened. Today, this fish is farmed all over the world in aquaculture, producing more silver carp by weight than any other species of fish other than carp.