Salmon farming endangers wild salmon
Parasites from salmon farms also infest the offspring of wild salmon as they migrate past the aqua farms. Up to 95 percent of the affected young animals die from it, so that the native populations can be extremely endangered.
Under natural conditions, the fry would not come into contact with the harmful sea lice (Lepeophtheirus salmonis) - a copepod species - at least at the beginning of their migration, as these mainly live on adult fish, which at this time are far from the coast in the stay in the open sea. However, the salmon farms are located in the immediate vicinity of the coast and in some cases increase the concentration of parasites in their vicinity by a factor of 30,000. After counting sea lice on around 14,000 juvenile salmon and monitoring the mortality rates of more than 3,000 animals off British Columbia, mathematicians and biologists led by Martin Krkošek from the University of Alberta in Edmonton finally calculated what impact this would ultimately have on wild stocks of ketal salmon (Oncorhynchus keta) and pink salmon (O. gorbuscha).
One or two sea lice per fish are enough to kill them through blood loss and disease. The infestation varies significantly seasonally: At the beginning of the migration of young salmon in early spring, the researchers only recorded a loss of nine percent of the animals, since the number of sea lice was still very low at that time. Only a few weeks later, however, this proportion rose to 95 percent, since the sea louse population had increased significantly by then. The researchers warn that even the low loss rates of ten percent - in addition to the already high mortality rate of young fish - quickly endanger the stocks. The previous concept of aqua farms close to wild salmon should therefore be reconsidered, says Krkošek.
