Silver Fish of Fuxian Lake

Silver Fish of Fuxian Lake

The Silver Fish of Fuxian Lake is a protected geographical indication product.

　　In 1982, silver fish were first introduced into Xingyun Lake. Whenever Xingyun Lake experienced flooding, the silver fish flowed into Fuxian Lake along with the water. By 1986, tens of tons of silver fish had entered Fuxian Lake from Xingyun Lake, while the production of anti-wave fish at that time was between 350 and 400 tons. In 1987, in coastal areas of Fuxian Lake such as Mingxing and Luchong, fishermen could still catch anti-wave fish using hooks. But they noticed that the anti-wave fish had become larger and thinner. “This is the result of competition (between anti-wave fish and silver fish),” said Zhang Peiqing.

　　　　How did they compete? After years of observation and research, Zhang Peiqing concluded that although both species feed on zooplankton, compared to the anti-wave fish, silver fish have a shorter growth cycle, smaller body size, and thus hold an advantage in competing for food and living space. For example, a pair of male and female silver fish, with the female carrying about 2,000 eggs, produces around 1,500 eggs, of which approximately 1,000 may be fertilized, and ultimately about 300 survive. The life cycle of silver fish is one year, so a single pair can reproduce about 300 offspring annually.

　　　　Generally, a female silver fish spawns twice a year, breeding in spring, maturing in autumn, and spawning again in the following spring before dying. In Fuxian Lake, juvenile silver fish around two centimeters in length can be caught year-round, indicating continuous reproduction throughout the seasons and a geometric increase in their population. In contrast, anti-wave fish take two to three years to mature, and captured specimens suggest a lifespan of over five years.

　　　　Faced with the “invasion” of silver fish, the anti-wave fish rose up to “resist.”

　　　　“In those years, scientific personnel from the former Fuxian Lake Management Station once found remnants of silver fish in the stomachs of anti-wave fish,” said Zhang Peiqing. “They were truly desperate!” He believed this indicated the intense and brutal ecological competition between invasive and native fish species. Confronted with the rapid proliferation of silver fish squeezing their habitat, anti-wave fish — which originally fed on zooplankton — were forced to change their diet. The outcome of this “resistance” was differentiation between the two species, each occupying its own niche: the anti-wave fish retreated to deeper waters, while the silver fish moved to nutrient-rich surface areas, or the two avoided direct encounters by foraging at different times. At the same time, their diets also diverged, with each species preying on different sizes of zooplankton. From then on, the competition between them eased somewhat.

　　　　Statistics show that between 1989 and 1991, the number of anti-wave fish in Fuxian Lake stabilized at around 250 tons, while the silver fish population reached 600 to 800 tons, achieving a temporary balance. “The subsequent imbalance was mainly due to human factors,” said Zhang Peiqing.

　　　　The human factors Zhang Peiqing referred to include three aspects: First, the use of mechanized fine-mesh nets and large drag nets at the time — “big nets catch small fish, small nets catch big fish” — which, while targeting silver fish, also swept away spawning anti-wave fish and their juveniles; second, damage caused during lake development, such as the filling of spawning grounds like those in Lichang, Chengjiang, and Haiguan, Huaning, during the construction of lakeside roads, and the occupation of shallow water feeding grounds by built structures; third, pollution from human activities (such as sewage discharge) contaminating the spawning waters of the anti-wave fish. For the “filth-fearing but shameless” anti-wave fish, this threatened their reproduction.

　　　　According to surveys, as early as six years ago, the annual production of anti-wave fish in Fuxian Lake had dropped to just 0.9 tons. Today, catching anti-wave fish in the lake has become extremely difficult, while the annual production of silver fish has reached 1,500 to 2,000 tons.