Impacts of Pesticides on Fish

Fish can be directly or indirectly impacted by pesticides. Some long-term exposures cause abnormalities or mutations in developing fish larvae, while acute exposure can cause immediate fish die-offs. The liver, kidney, brain and gills of exposed fish are extremely vulnerable to chemical exposure.  Linking pesticides to be the cause of harm to fish can be difficult because they are highly mobile animals, and the effects may not show until much later in life.

  • A 2015 study showed that when fish larvae are exposed to pesticides through water contamination from runoff, they can develop swimming abnormalities as they grow, making them an easy target for prey and impacting their survival rate.
  • Wild Steelhead
    Wild Steelhead. Photo by USFWS - Pacific Region.
    In 2012, thousands of fish were found dead in Prince Edward Island, Canada, due to pesticide runoff from nearby agricultural fields after heavy rain. In 2013, dozens more dead fish washed ashore, again after heavy rains and possible pesticide exposure.
  • In 2012, the National Marine Fisheries Service (NMFS) drafted a biological opinion to the Environmental Protection Agency (EPA) concluding that three herbicides (oryzalin, pendimethalin, and trifluralin) pose a direct threat to approximately 50% of endangered Pacific salmon and Puget Sound steelhead species, and adversely impact their habitat.
  • Fish species are also sensitive to endocrine disruptors. In 2005, researchers in British Columbia, Canada, demonstrated that biological changes induced by sublethal exposure to pesticides include inhibition of important enzymes and growth delay.

Economic Cost

Fisheries are valuable resources that are enjoyed by millions of Americans. Fish provide food services for humans and other wildlife. They also provide benefits for citizens through direct financial gain or recreational enjoyment. For example, the seafood industry provides jobs for commercial fishers and retailers, while the other aquatic areas provide the opportunity for recreational activities such as sport fishing.  

One estimate for the economic cost of the impacts of pesticides on fish uses information provided by EPA’s fining of Coors Beer for river pollution ($10 per fish). With this information, it is assumed that the economic value of fish killed by pesticides each year is estimated to be $10-25 million. This is most likely a vast underestimate, as fish kills due to pesticides are hard to trace (see David Pimentel’s 2005 study for more information). A separate study has estimated that the entire value of recreational fishing is worth $27.9 billion annually. From this estimate, one can assume that as fish kills due to pesticides increase, there will be less available fish for recreational fishing. As the supply decreases, the cost will increase, leading to increased spending by citizens who partake in this activity.

Litigations & Lawsuits

In 2008, more than 13 organizations filed a legal petition demanding that EPA regulate novel nanomaterial pesticides. EPA remained silent, prompting Beyond Pesticides and other organizations to sue the EPA in 2014. Silver nanoparticles are often impregnated into a wide variety of consumer products. These nanoparticles are released when washed, where they exit down the drain and enter into the environment. These products have been found to be toxic and potentially lethal to fish. In early 2015, the EPA finally responded and agreed to regulate these novel nanomaterials as pesticides.

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Juvenile Coho Salmon
Juvenile Coho Salmon. Photo by USFWS - Pacific Region

In 2010, Earthjustice, representing the Pacific Coast Federation of Fishermen’s Associations, the Northwest Coalition for Alternatives to Pesticides, and Defenders of Wildlife, filed litigation that called for EPA adoption of reasonable fish protections from insecticides. Following the Lawsuit, EPA restored stream buffers to protect salmon from pesticides. The buffers apply to salmon habitat throughout California, Oregon, and Washington to prohibit aerial spraying of broad-spectrum pesticides diazinonchlorpyrifosmalathion, carbaryl, and methomyl within 300 feet of salmon habitat and prohibit ground-based applications within 60 feet.

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