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Two goldfish fished in a rain pool in the Toronto area. (photo: Christine Boston / Canadian Fisheries and Marine Department) the goldfish we are familiar with always swim in the fish tank in a mini and lovely image, but on the other side of the ocean, this seemingly harmless creature kills everywhere in the ecological environment.

In the summer of 2021, biologists discovered more than 20, 000 goldfish in a rain pool the size of two basketball courts (stormwater pond, an artificial body of water used to lower flood peaks and balance Rain Water's flow rate in the drainage system) west of Toronto, Canada. These goldfish are probably the offspring of domestic goldfish, which are not only rampant, but some individuals have even grown into giants weighing up to 3 pounds (about 1.4 kg). To facilitate the collection of Rain Water and runoff, cities in North America have been building Rain Water ponds for the past 40 years, but invading goldfish have grown savagely in these thousands of Rain Water ponds.

Ecologists from the University of Toronto and the Canadian Fisheries and Marine Department (DFO) are jointly investigating whether these heavily polluted and harsh Rain Water ponds give super-resistant goldfish a greater survival advantage, and what is the mechanism. If people ignore this, these goldfish are likely to occupy the nearby Great Lakes and eliminate native species there. Nicholas Mandrak, a conservation biologist at the University of Toronto at Scarborough, who participated in the project, asked his own question: "with climate change, these 'super invasive fish' may have a growing impact on the ecology. Are we human beings responsible for their existence?"

From ornamental fish to invasive goldfish, goldfish is a kind of ornamental fish native to East Asia, which may initially enter the Great Lakes and rivers of North America through the ship's ballast water (ballast water, water injected into specific cabins to adjust the ship's float and stability and improve the ship's navigation performance). Mandelak estimates that some small local populations may have lived in these bodies for 150 years. Anthony Ricciardi, a professor of invasive species and ecology at McGill University in Canada, who worked with Mandelak but was not involved in the project, believes that no matter what new habitat the goldfish enter, they are harmful to the local environment.

Photo Source: Hans / Pixabay one of the reasons is that the eating process of goldfish can disturb the surrounding environment. They swallow the tiny sediments at the bottom of the lake and river, turn them over in their mouths, then spit out the sediment and inhale the food that falls from it. As a result, goldfish will uproot many aquatic plants and make the water turbid, resulting in less light in the water, so aquatic plants may eventually die from lack of light. Rich Yadi added that goldfish have transformed their habitats with this destruction, but worsened the living conditions of species that hunt visually or rely on light to survive.

Although these invasive goldfish have lived in North America for a long time, their numbers have increased sharply in rain pools everywhere and in some port waters of the Great Lakes with the continuous construction of the city's Rain Water ponds in the past decade. Biologists speculate that most of the goldfish in Rain Water's pond were originally introduced by humans because the goldfish in the lake are unlikely to swim against the current into these isolated ponds located upstream. Most fish species cannot survive in Rain Water ponds because the environment in these ponds is harsh and unstable, not only the water level fluctuates frequently with rainfall, but also because of its shallow depth, the oxygen content in the pond water is very low and the water temperature is relatively high. However, these goldfish have evolved a special metabolic system that allows them to sometimes survive in an environment without oxygen for up to five months.

Potential crisis Christine Boston (Christine Boston), a fish production biologist at the Canadian Fisheries and Marine Department, believes that scientists are worried that goldfish can gain a competitive advantage over native species because of the decline in oxygen levels in rivers and lakes as a result of global warming. If these goldfish really have such a competitive advantage, after the goldfish in the urban Rain Water pond flow into the natural wetlands, they may be more destructive than the current wild goldfish population. To gain further understanding, Mandelak and colleagues are comparing goldfish populations in Rain Water ponds and natural habitats to study their survival in the current and future warming environments.

In the summer of 2021, the team investigated the temperature tolerance of goldfish in two Rain Water ponds. The researchers put the goldfish in the water and slowly heated the water, and when the goldfish could no longer maintain their upright posture, the water temperature had reached their maximum tolerance. Mandelak plans to test the temperature tolerance of goldfish in 24 other Rain Water ponds this summer, compare it with the overall temperature tolerance of wild populations in the Great Lakes region, and hope to eventually find specific genes that regulate the temperature tolerance of goldfish. At the same time, determine whether there are differences in related genes between wild fish and fish in ponds, and if there is a difference, it means that evolutionary adaptation has taken place.

Scientists investigate one of the Rain Water ponds, and they hope to find goldfish that can adapt to the harsh aquatic environment. (photo: Christine Boston / Department of Fisheries and Oceans of Canada) this research project also reveals some of the environmental features of Rain Water Pool. These ponds are usually less than 6 feet deep and the water is usually warm. Ponds tend to have a high salt content because snow removal salt sprinkled on roads in winter flows into the pond. In addition, the use of chemical fertilizers makes these Rain Water ponds often eutrophicated. Boston points out that overheating and eutrophication can lead to lower oxygen levels in the water. She is also developing a sampling method for environmental DNA (eDNA) to detect the genetic material of goldfish in a small number of water samples. After mastering the environmental characteristics of Rain Water Pool, Fisheries and Marine Canada can also identify "high-risk" ponds where goldfish may inhabit, and then use eDNA samples to quickly determine which species are present in the environment. If goldfish are detected in the sample, people can block the pond from draining into nearby waterways, reducing the risk of these highly tolerant goldfish entering natural water bodies.

Experts such as Mandrake, Boston and Richiardi all agree that the focus of future work is on prevention to better manage these super invasive goldfish. For example, signs are placed around the pond to advise people not to release pet fish that they no longer want to keep, but to send them back to the store or give them to friends. In addition to advice to the public, Boston advised land developers and engineers to reconsider the design of rain pools to prevent the proliferation of goldfish or other invasive species, such as building barriers between rain pools and adjacent waterways. or put large amounts of goldfish in the pool, such as the big-billed bass (which are already native to these areas).

Boston and other biologists look forward to fully understanding the threat of invading goldfish as soon as possible to prevent them from endangering local fish breeding grounds and wetlands downstream and causing irreparable consequences. "before fully assessing their potential risks, we should try our best to prevent these goldfish from entering the wild environment." Mandelak appealed to this.

Original text link:

Https://www.scientificamerican.com/article/supersized-goldfish-could-become-superinvaders

This article comes from the official account of Wechat: global Science (ID:huanqiukexue), written by Hannah Hannah Loss, translated by Fan Jiahao, revised by Li Shiyuan

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