Wild pink salmon in northwestern Canada are at high risk of death and could soon disappear because of sea lice from fish farms in the region, says a study led by Canadian researchers.

The sea lice, also known as Lepeophtheirus salmonis, are natural parasites that latch onto the fishes’ skin. Salmon lice attach themselves to the exterior of pink salmon and feed on surface tissue like skin, blood and muscle and can cause stress, viral or bacterial infection and ultimately death, the researchers said. They usually infect adult salmon, but they can tolerate mild infestations. Juvenile salmon on the other hand, are vulnerable to survive an infestation because their skin is too thin.

Young fish are not at risk in the wild, where they generally do not interact with any infected adult salmon as they swim out to sea. The danger is represented by the fact that they can become infected with sea lice as they swim past nets full of infected farmed Atlantic salmon on their way back and forth to sea.

Researchers from the University of Alberta, Dalhousie University and the Salmon Coast Field Station in Echo Bay, B. C., said that the population of wild salmon will drop 99 percent in four salmon generations or about 8 years if outbreaks of sea lice continue at their present rate.

They studied a 400-square-mile area along the coast of British Columbia where wild salmon migrate past salmon farms when traveling from inland streams to the open ocean. The researchers looked at Canadian official data about pink salmon dating back to 1970. Salmon farming began to appear in the late 1980s, but sea lice infestation began only in 2001. There are currently more than 20 salmon farms in the investigated area, creating a habitat for sea lice that will overwhelm the wild salmon if immediate measures will not be taken, researchers said.

“The impact is so severe that the viability of the wild salmon populations is threatened,” said Martin Krkosek, lead author of the study, which appears in Friday edition of the journal Science.

The study reveals worrying data, saying that sea lice have killed more than 80 percent of the annual pink salmon and predicts that the population will be wiped out in just four years if salmon farms do not change their practices.

“Salmon farming breaks a natural law. In the natural system, the youngest salmon are not exposed to sea lice because the adult salmon that carry the parasite are offshore. But fish farms cause a deadly collision between the vulnerable young salmon and sea lice. They are not equipped to survive this, and they don’t,” said co-author Alexandra Morton, director of the Salmon Coast Field Station in the archipelago.

The researchers came also with a solution for this problem.

"The solution is simple. Build a better barrier to separate the older salmon from the younger salmon," Morton said.

This barrier would prevent transmission of lice in infested farms from reaching the young salmon in the wild. She also added that this measure could be expensive, but it is the only way to prevent the salmon extension.

There were also other scientists predicting the extinction of pink salmon. Last year, marine ecologist John Volpe of the University of Victoria said in a study published in the Proceedings of the National Academy of Sciences that sea lice from fish farms kill up to 95 per cent of juvenile salmon that pass by.

However, the study appeared today is the first to predict such large-scale losses of wild fish from sea lice from farms.