Scientists have noticed that a large number of Coho salmon have been dying in the streams and rivers along the West Coast where they return from the Pacific Ocean to spawn. They have seen that the fish have been dying in huge numbers after heavy rain events each fall before they spawn. These mysterious incidents have been a subject of research for many years. Now, scientists believe that they have found a reason behind this mystery. They have said that a chemical antioxidant called 6PPD, which is used in tires around the globe, might be the reason behind the mysterious death of Coho salmon. This chemical compound is scattered all over North America’s roadways, as per the experts. Experts have said that when tires’ treads break down with time, it leaves tiny bits of microplastics on roads. The 6PPD present in tires reacts with ozone and converts into a different chemical called 6PPD quinone.
Experts have said that the substance is toxic to Coho salmon. They have found it in roadway runoff samples extracted from across the West Coast. It has led them to the conclusion that this substance is the main cause of the declining population of Coho salmon. The findings of the study have been released in the journal called Science. The outcome of this study will be a crucial step towards ensuring the existence of these salmon, said the experts. The lead author of the study, Dr. Ed Kolodziej has said that the findings of the study will allow authorities to solve such problems effectively. Coho salmon are the favorite salmon of sport fishermen out of five salmon species found in the Pacific Northwest’s forest. Coho salmon have huge cultural significance across many of the region’s Native American tribes. These salmon are a vital part of the food cycle as well. The lead author of the study has said that the existence of spawning Coho is a sign of the overall health of an ecosystem. The mysterious death of these salmon is a clear sign of forthcoming disturbance in the ecosystem.
Coho salmon found in Central California have been classified as endangered species. The US Fish and Wildlife Service has listed three other populations of Coho salmon as threatened under the Endangered Species Act. As per the data, in a healthy stream, less than 1 percent of Coho salmon die before spawning. Experts warn that around 40 to 90 percent of the fish are likely to perish in the most affected streams during these mysterious mass death events. The co-author of the study has said that they have been keeping the records of these mysterious death events since the early 2000s. The study has shown that nearly 3.1 billion tires for more than 1.4 billion vehicles in the world are manufactured in a year. This chemical is used in almost all of them. Past studies have revealed that tire abrasion is one of the most important sources of microplastics in the marine ecosystem. Tire abrasion contributed to 30 percent of total microplastics in the aquatic ecosystem. Experts have said that there is a need for better treatment and management of runoff before it reaches coastal streams.
