Case of the Missing Atlantic Salmon

Numbers of Atlantic salmon have fallen by 90 percent over the past two decades, and Pacific salmon also are in serious trouble

• NWF Staff
• Feb 01, 2000

When many sewage-treatment plants, pulp mills and other industries discharge a substance called 4-nonylphenol into waterways, are they playing an unwitting role in the decline of North America´s salmon populations? That´s a question being asked by Canadian scientists that have studied the relationship between poor runs of Atlantic salmon and the use of a certain pesticide in the 1970s and 1980s to control spruce budworms in Canada.
The researchers found a clear trend: Salmon populations that would have been exposed to 4-nonylphenol in the pesticide on their way to the sea later returned in far fewer numbers than other populations. Comments biologist Wayne Fairchild of Canada´s Department of Fisheries and Oceans, "The more that was sprayed, the fewer fish returned." Either as an ingredient itself or as a breakdown product of other chemicals, 4-nonylphenol often is found in the manufacture of a broad range of products that include textiles, plastics, cosmetics and spermicides. It also is discharged in the effluent of many industries located along waterways.

Normally salmon smolts go through hormonally driven changes enabling them to make the switch to salt water. But in the lab, the Canadian team found evidence that 4-nonylphenol may sabotage that process. Other research has found that estrogen interferes with the hormonal messages involved in the adaptations of salmon to salt water. And 4-nonylphenol is one of many man-made chemicals that can make cells react as if it were estrogen.

Numbers of Atlantic salmon have fallen by 90 percent over the past two decades, and Pacific salmon also are in serious trouble (Read more in the February/March 2000 National Wildlife Magazine Article "When a Fish Is Not Just a Fish"). Factors already known to affect the fish include dams, overfishing and habitat changes due to logging and grazing.