Sockeye salmon are exposed to a soup of chemicals in the Fraser River, and some of the ingredients are accumulating to potentially lethal levels in eggs, while others may be disrupting the sexual function of fish, according to a scientific review conducted for the Cohen Commission.
The study states that because of key data gaps, it is not possible to reach a definitive conclusion about exactly how the 200 contaminants identified in the river have affected the growth, survival rates or reproduction of salmon.
While it is unlikely that contaminants are "the sole cause" of sockeye population declines, the report says there is "a strong possibility that exposure to contaminants of concern, endocrine disrupting chemicals, and/or contaminants of emerging concern has contributed to the decline of sockeye salmon."
The report, by McDonald Environmental Sciences Ltd., a Nanaimo-based research firm, identified numerous chemicals in surface waters and in bottom sediments that posed potential risks to sockeye, including nitrate, chloride, sulphate, arsenic, mercury and selenium.
It said some of the chemicals exceeded toxicity levels for fish and it noted that "water quality conditions have degraded over the past two decades."
The report also says research done in 2001 and 2004 found some chemicals were concentrating in the eggs of sockeye at toxicity levels "associated with 30 per cent mortality of fish eggs."
There were no studies to determine if eggs were in fact being damaged by chemicals, but the report says fish that had a long way to swim before they spawned, and thus had more time to accumulate chemicals, were at the greatest risk of having high concentrations in their eggs.
"These. . .results suggest that PCBs, PCDDs, and PCDFs could be adversely affecting sockeye salmon reproduction," states the report.
Polychlorinated dibenzo-p-dioxins (PCDDs) dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) are a group of dioxins typically formed through combustion, such as in commercial or municipal waste incineration and from burning fuels.
The study said selenium, a naturally occurring chemical element that can cause contamination when released in volume in wastewater, and another dioxin, 2,3,7,8-Tetrachlorodibenzodioxin (TCDD), were also found in sockeye eggs, representing "a potentially important factor influencing the status of sockeye salmon populations."
The report said data on the bioaccumulation of toxic substances were limited and need further evaluation.
An array of metals, including aluminum, chromium, copper, iron and silver were found in bottom samples, but the contaminated sediments weren't thought to be contributing to the decline of salmon because of limited interaction between fish and sediments.
One group of pollutants of concern were endocrine disrupting chemicals, which can affect growth, development and sexual reproduction.
Among the endocrine disrupting ingredients identified in the Fraser were industrial chemicals, pesticides, compounds with a carbon-metal bond, pharmaceuticals and "several estrogen-like compounds," the report says.
It states that data are insufficient to evaluate the impact of endocrine-disrupting compounds, but notes reports from First Nation fishermen that salmon are smaller on average, increasingly have blotchy skin and of one male sockeye that had ovaries, are cause for concern.
"Such changes in salmon physiology are not unlike those that could occur in response to endocrine disrupting compounds and/or other contaminants," the report states.
The report is one of several science studies ordered by the Cohen Commission, which was appointed by Prime Minister Stephen Harper to investigate the decline of sockeye after only one million fish returned to spawn in 2009, when more than 10 million were expected.
The inquiry is headed by British Columbia Supreme Court Justice Bruce Cohen, who is holding evidentiary hearings in Federal Court in Vancouver.