The species of the large-scale money eel glue is the Totoaba of The Mexico, which comes from the Gulf of California, Mexico, which was once abundant, but due to overfishing caused by market demand, the population has plummeted, and now the Totoaba of the Mechsonium is endangered.
1. The change of habitat environment has greatly reduced the survival rate of juvenile fish
In 1931, the United States built the Hoover Dam on the Colorado River, the most turbulent and deepest river, and diverted it. The Hoover Dam is a world-renowned water conservancy project, one of the most influential and challenging public water conservancy projects in the history of Western science and technology in the 20th century. The completion of the Hoover Dam has retained the amount of fresh water from the Colorado River into the Gulf of California, changing the salinity of the Colorado Delta and greatly reducing the survival rate of juvenile fish.
2. Overfishing has led to a sharp decline in the number of head fish
The United States began importing fish meat in the 1920s and is the main consumer market for fish meat. The demand for fish meat in the United States and the consumption of the head maw (i.e. large-bearded money eel glue) in the Chinese market have exacerbated the problem of overfishing.
At the same time, with the continuous development of lensnet and trawling fisheries, as well as the continuous improvement of equipment, the head fish is caught in large quantities. During the migratory spawning season, overfishing suddenly causes a sharp drop in the number of mature females. The loss of a large number of mature females means the loss of the ability to replenish their offspring and maintain their populations, which eventually leads to a sharp decline in the birth rate of the headfish. At the same time, the developed trawler shrimp industry has attracted a large number of juvenile fish into the by-fishery. According to statistics, 120,000 juveniles died each year in trawl shrimp fishing operations in the mid-1980s.
3. From a biological point of view, the generation length of the head fish is long, and the low reproduction rate leads to a downward trend in its population.
It is generally believed that the lifespan of the head fish can reach 25 years. The first generation of breeding females and males are 6 and 7 years old respectively, i.e. from the time of spawning, it takes 6 years for females to reach sexual maturity and 7 years for males.
The cycle of development from the time the egg leaves the mother to the time of sexual maturity and the beginning of spawning is called a generation. Generation is the average age of the previous generation of the current group. Thus, the generation length reflects the turnover rate of the reproductive individuals in a population. The generation length is estimated at 19 years based on the average estimated age and maximum lifespan of the first generation of the species after 7 years and a maximum of 30 years. Therefore, the longer the generation length and the low reproductive rate of the headfish, coupled with its inherent natural mortality rate, have led to a continuous decline in its population.