When it comes to mosquito-eating fish, I believe many people are not strangers. Mosquito-eating fish are native to the ditches and streams of the United States and Mexico, feed mainly on the larvae of mosquitoes, and are well-known "mosquito killers" in North America.
Since 1905, mosquito-eating fish have been introduced by various countries, the main purpose is to prevent the spread of mosquitoes and malaria. The introduction of mosquito-eating fish in China can be traced back to 1927, but in the following decades, mosquito-eating fish gradually gained a foothold in the inland waters south of the Yangtze River, establishing a large population and also bringing a huge impact on China's native species.
Mosquito-eating fish (scientific name: Gambusia affinis)
Today, mosquito-eating fish have become the world's most wanted object, except for Antarctica, the distribution of mosquito-eating fish in temperate and tropical regions on all continents of the world. Due to the ecological harm caused, mosquito-eating fish are also included in the list of 100 most threatening invasive alien species in the world.
<h1>Mosquito-eating fish: it is a "mosquito killer", but also an "ecological killer"</h1>
When mosquito-eating fish were introduced to Turkey, local researchers specifically studied the feeding habits of mosquito-eating fish. The results showed that mosquito larvae accounted for 32.8% of the intestines of adult mosquito-eating fish, while the proportion of juvenile mosquito-eating fish was as high as 64.8%, which shows that mosquito larvae do account for a large proportion of the nutritional structure of mosquito-eating fish.
Mosquito larvae
Another survey also showed that at a water temperature of 23 °C, a 1.1 g mosquito-eating fish can eat 438 mosquito larvae in a single day, and the combined weight of these larvae reaches 1.6 grams – heavier than the weight of the mosquito-eating fish itself. These studies are enough to show that mosquito-eating fish are indeed veritable "mosquito killers".
However, what is surprising is that the other identity of the mosquito-eating fish is an out-and-out "ecological killer", which has caused a lot of species survival crisis in the world.
In southern California, the local salamander quickly disappears from streams introduced to mosquito-eating fish, while in streams that do not introduce mosquito-eating fish, salamander larvae and adults live well. Even more worrying to ecologists is the fact that the Pacific tree frog has also been affected by mosquito-eating fish, and the tadpole of the tree frog appears about 65% more frequently in the stomach of the mosquito-eating fish.
The range of mosquito-eating fish in the United States is expanding
In Australia, the green-bellied frog is an endangered and rare frog, but after the introduction of mosquito-eating fish, the replenishment of the adult population of the green-bellied frog was significantly reduced, and the species was on the verge of extinction. In Spain's Iberian Peninsula, the wild population of 2 species of tooth carp has also been affected by mosquito-eating fish - mosquito-eating fish have successfully "ascended to power" after "settling" in the peninsula, frantically eating the eggs of tooth carp, resulting in a significant decline in fishery production and economic benefits.
There are many similar cases, these are blindly introducing mosquito-eating fish and being issued "ecological fines", which are also naked lessons.
<h1>So the question is: why do small mosquito-eating fish flood the world? </h1>
Mosquito-eating fish were introduced to reduce the risk of mosquito-borne diseases, and some areas were introduced as ornamental fish. Although the starting point is good, the strong reproductive ability of mosquito-eating fish has made this species more and more uncontrolled, and the situation has completely deviated from the original idea.
Size comparison of male and female mosquito-eating fish: female individuals are significantly larger than males
The reason why mosquito-eating fish can be widely distributed around the world has a lot to do with its special reproductive mode and strong reproductive ability.
Unlike ordinary freshwater fish, mosquito-eating fish reproduce in the form of egg-born eggs – fertilized eggs hatch in the female's body and develop into juveniles. Because the risk of death during hatching is successfully avoided, the survival rate of mosquito-eating offspring is much higher than that of ordinary oviparous fish, which is also "out of reach" by most indigenous fish.
Developmental Atlas of Mosquito-Eating Fish: The processes in the above figure are completed in the female fish
After the mosquito-eating fish is born, it only takes up to 50 days of development time to reach sexual maturity, and if the water temperature conditions are suitable, then it can start to breed offspring in at least 30 days - this development rate of the mosquito-eating fish is much more exaggerated than that of tilapia, almost 3 times that of the latter.
In the wild, mosquito-eating fish generally live no more than 2 years, but the breeding period is particularly long. In Guangdong, Hainan and other places, mosquito-eating fish can breed normally from the beginning of April to the end of November, with more than 240 days of breeding time in a year. In tropical areas such as Hawaii, mosquito-eating fish can breed all year round due to the suitable water temperature.
Adult and juvenile mosquito-eating fish
Not only that, but each mature female can reproduce multiple times, which can be called a powerful "fertility machine". In the spring breeding group, the female fish can generally produce 3 to 5 batches of juvenile fish, and the number of each litter is more than 10, and these calves can mature and join the new round of "breeding army" in the autumn of that year.
<h1>Mosquito-eating fish invaded China, yunnan into the "hardest hit area"? </h1>
Since the 1960s, mosquito-eating fish have been introduced to the natural waters of Yunnan and are now found in Dianchi Lake, Xingyun Lake, and Dali West Lake. Due to their fierce temperament and strong fecundity, mosquito-eating fish soon began to compete ecologically with the local Chinese medaka, resulting in a sharp decrease in the number of wild medaka in Yunnan.
Blue mackerel (aka Japanese rice field fish)
Chinese medaka is an indigenous fish species in Yunnan, after the introduction of mosquito-eating fish, the living space of the native medaka has been gradually compressed, and eventually confined to some scattered small habitats, and in some areas the medaka has even completely disappeared.
According to some old fishermen in Yunnan, around 1973, the fish ponds on the banks of the Lancang River could often see medaka swimming back and forth, and the number was still very large at that time. But by 1986, the alien species of mosquito-eating fish soon conquered this area of water, driving the medaka out of the "extermination", and the wild medaka in the Jinghong area has basically disappeared.
Artificial stocking is the "fuse" for mosquito-eating fish to flood in the wild
▲In October 2014, Guangzhou launched an anti-mosquito activity in Guangzhou, and in Luoyong Park in Baiyun District, the staff brought more than 1,000 mosquito-eating fish to the pond for mosquito control.
In addition to Yunnan, tilapia in the Pearl River Basin has also been hit by mosquito-eating fish. In China, tilapia is also a well-known exotic species, which has developed into an important farmed species. In the Pearl River Delta region, wild mosquito-eating fish and tilapia often coexist, and the two alien species inevitably compete fiercely.
Wild tilapia in the Pearl River Basin
Unexpectedly, mosquito-eating fish are likely to be potential "tilapia killers". In 2011, researchers conducted a study of mosquito-eating fish in the Pearl River Basin and unexpectedly found three tilapia larvae in the digestive tract of a 2.4 cm long female mosquito-eating fish with a body length of 5.6 to 6.6 mm.
▲ As shown in the picture above, tilapia broodstock will contain fish eggs in the mouth to hatch, and mosquito-eating fish have no opportunity during this period. However, after hatching, the juvenile fish need to separate from the mother to feed on plankton autonomously, and the juvenile fish may be eaten by mosquito-eating fish.
The discovery has raised concerns among domestic experts: if tilapia is the prey of mosquito-eating fish, then indigenous fish species such as the four major fish, mud carp, Cantonese bream and seven-silk squid in the Pearl River Basin are likely to face similar dilemmas.
It is undeniable that in the rivernet region of the Pearl River Delta, mosquito-eating fish has become one of the most common exotic fish species (tilapia is also common), but the number of indigenous fish is decreasing. The water temperature conditions of the Pearl River are very suitable for the growth and reproduction of mosquito-eating fish, and if they are not controlled, they are likely to develop into a huge ecological hidden danger.
▲The above figure is the distribution map of alien species in 8 major rivers in South China, and the situation in the Pearl River Basin is not optimistic.
<h1>summary</h1>
Mosquito-eating fish are highly adaptable and fertile, causing a lot of ecological crises in the United States, Australia and European countries. In China, the extinction of some indigenous fish species has also become an irreparable "species disaster".
It wasn't until the 1990s that people began to realize the seriousness of mosquito-eating fish invasions. However, for a long time to come, mosquito-eating fish will continue to spread due to human release, natural migration and other factors. For us ordinary people, the best thing to do is to strengthen the awareness of ecological protection and avoid blind release - this way is the lowest cost and the best effect.
#Mosquito-eating fish ##Species invasion##Tilapia ##保护生态 #