In its bowl, the goldfish is rather cute and friendly. However, when individuals throw it back into rivers, it becomes a real monster embodying one of the most invasive aquatic species in existence.
Reject his goldfish Carassius auratus is a serious attack on the environment, more precisely on the ecosystem of the area where it is precisely released. It attacks aquatic plants by uprooting them, stirs up river sediments and can also carry potentially fatal diseases or parasites for other species, in addition to devouring their eggs.
To illustrate the problem, you have to go to Australia, to the Vesse River located in the southwest of the country. Fish have been released into this stream for two decades now. Thus, the specimens found there today can reach 40 centimeters in length and a weight of 2 kilograms. Yes, it is the little goldfish in our bowl!
However, clarifications deserve to be made. Not all goldfish released into the wild become like this. Indeed, the population of Vesse River has especially experienced an increase since the watercourse brings them nutrients in greater numbers due to the surrounding agricultural activities. The ambient temperature, often exceeding 30°C, also favors their proliferation.
In 2003, a control program was launched, but their number does not seem to have changed. Recently, researchers from Murdoch University (City of Perth) tried to understand the rhythm of life of these extraordinary goldfish. The scientists used passive acoustics, studying the noises resulting from the movements of around fifteen fish, picked up by a network of hydrophones.
The results of the study, published in the journal Ecology of Freshwater Fish on August 12, 2016, show that goldfish adapt their movements according to the seasons. Indeed, during the breeding season, they move towards calm waters. Researchers have also noticed that goldfish can travel quite a distance. One of the specimens had even swum 230 km in one year! They are therefore able to colonize other environments.
According to the scientists, it is possible to limit the proliferation of the species by preventing its access to breeding areas and more generally, by strongly limiting its movements. Of course, it is a question of not worsening an already very worrying situation, so you will have understood it, avoid throwing your (small) goldfish in a river.
Sources: Sciences et Avenir – Le Matin