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Study Suggests Link
Between Past Chemical Use
and Declines in
Wild Salmon Populations

  Wayne Fairchild,
  Environment Canada
  January 7, 1999

recently released study conducted by researchers with the Department of Fisheries and Oceans (DFO) and Environment Canada has found that past chemical use may have had an effect on wild salmon populations in Atlantic Canada. The study demonstrates a relationship between chemical use and salmon survival, thus providing another factor to be considered when evaluating the sustainability of the resource.

(Photo:http://ceres.ca.gov)

Dr. Wayne Fairchild, Jacqueline Arsenault and Erin Swansburg from DFO’s Gulf Fisheries Centre in Moncton, New Brunswick, and Dr. Scott Brown from Environment Canada’s, National Water Research Institute in Burlington, Ontario, studied the historical relationship between spraying in Atlantic Canada’s forests and subsequent salmon returns to their local rivers during a ten year period from 1975 to 1985. Their concern was that during this time period, one of the insecticides sprayed, Matacil®1.8D, contained high concentrations of a compound called 4-nonylphenol (4-NP). From laboratory studies, these nonylphenols, which are classified as Endocrine Disrupting Chemicals (EDCs), are known to be toxic to invertebrates and fish and to have estrogenic effects. This study will contribute to the understanding of EDCs and their effects in the environment.

In the spring of 1997, the team began to compare data collected from spray maps of the Canadian Wildlife Service, Annual Reports of the Forest Pest Control Forum and other provincial monitoring reports, with data collected on Atlantic salmon runs from DFO reports and Canadian Atlantic Fisheries Advisory Committee reports. "What we found is that for one river, there was an association between the amount of Matacil®1.8D sprayed in 1977 and the number of salmon returning 2 years later. The more that was sprayed, the fewer fish returned," explained Fairchild. There was also a broader event of unusually heavy salmon smolt mortality in 1977. This smolt mortality event contains a significant relationship suggesting that where Matacil®1.8D spraying occurred, there was greater smolt mortality.

In addition, sixteen rivers in Newfoundland and New Brunswick exposed to spraying between 1973 and 1990 were evaluated and the results indicated that a significant number of the lowest salmon catches coincided with Matacil®1.8D spraying. In 1980, Matacil®1.8D was phased out of spray formulations for New Brunswick forests and replaced with Matacil®1.8F, a compound that did not contain 4-NP. There was no significant relationship found between spraying Matacil®1.8F and salmon returns. The study also found a decline coinciding with the use of Matacil®1.8D and blueback herring catches in New Brunswick.

Atlantic salmon are an anadromous species with a complex life history. Eggs are deposited in freshwater nests made on the gravel bottom in late October and early November. After hatching, salmon go through 4 stages in freshwater; alevin, fry, parr and smolt. This process requires 2 to 3 years. After reaching a certain size, the parr undergo a series of physiological changes to adapt to seawater and are then called smolts. The smolts will live in pools or the mouth of the river before migrating to sea in May or June. Once the smolts have left the river system, monitoring of their progress at sea is difficult. After one or more years at sea, Atlantic salmon will return to their natal river to spawn.

Matacil®1.8D was used as an insecticide to control damage from the spruce budworm. A single or repeated dose could be expected to reach many salmon streams between mid-May and mid-June, depending on the year and timing of the spray program to match the local development of the spruce budworm larvae. After spraying, it is estimated that the concentrations of 4-NP in the water was in a range which was not sufficient to immediately kill the salmon but may have caused estrogenic effects on the salmon. The researchers realised that the spraying coincided with the final stages of smolt development, and when looking at this time frame, effects on salmon populations were apparent.

"What is unique about this study with Matacil®1.8D is that there are very few examples where we can show effects of a chemical on wild fish populations. For EDCs, typically studies have focused on the reproductive system of fish. This study looks at the effects on smoltification and, although it has endocrine hormone involvement, the effects are not on the reproductive system of the fish where they might be expected," stated Fairchild.

The researchers next questions were "Does nonylphenol really affect Atlantic salmon? Does it cause the fish to die or are the changes more subtle?" In the spring of 1998, working at DFO’s St. Andrews Biological Station, a pilot study was conducted to look at the effects of NP on smoltification. The preliminary results indicated that yes, NP concentrations can interfere with the smoltification process so that some salmon do not survive the transition from fresh to saltwater. This study will be repeated next year looking at various concentrations and their effects. The focus will be to look at how 4-NP effects the smoltification process, a process that is known to be influenced by hormonal changes in the fish.

While Matacil® 1.8D is no longer used in forest spraying, levels of 4-NP that were found in forest streams after its spraying are currently found in today’s discharges from sewage treatment plants and other industrial effluents, often as a breakdown product of nonylphenol ethoxylates (NPEs). NPEs are used in household and industrial cleaning products, paints, pesticides and in industrial processes such as pulp and paper, textile manufacturing, petroleum production and leather manufacturing. While many countries, including Canada, are looking at the levels of NPEs in the environment, an immediate solution or alternative is unlikely because of their widespread uses. Nonylphenols are on the Priority Substance List II of the Canadian Environmental Protection Act that will contribute to regulations on their future use. For Atlantic salmon, if the mechanism of effect on smoltification is due to the estrogenic potential of 4-NP, then many other endocrine disrupting compounds encountered in the environment may also be important.

Under funding from DFO and Environment Canada, the research team will now focus on continuing research efforts on the potential effects of estrogenic compounds, such as 4-NP, on salmon smolts. In addition to the laboratory study mentioned above, the researchers will look at exposure levels of fish in the environment. The fish will be held in various places in rivers, near potential point sources and reference sites to determine the effects of present day effluents on the smoltification process. Researchers from Department of Fisheries and Oceans (W. Fairchild, J. Arsenault, K. Haya, L. Burridge) and Environment Canada (S. Brown, D. Bennie, J. Sherry) will be combining their efforts with university researchers from the University of Manitoba (J. G. Eales) and University of New Brunswick Saint John (D. McLatchey) to address this important question.