03
Jun
Threat to Ocean Health: Pesticide Resistant Fish Lice Plague the North Atlantic Ocean
(Beyond Pesticides, June 3, 2021) A report published in Royal Society Open Science finds pesticide-resistant parasitic lice (Lepeophtheirus salmonis) are endangering wild and farmed fish populations in the North Atlantic. Extensive use of pesticides to rid the parasite has led to widespread resistance to multiple pesticides, prompting increasing infection rates among North Atlantic salmon populations. Overexploitation of wild fish and other ocean organisms has depleted seafood stocks globally. Some fisheries market aquaculture practices, like fish/seafood farming, as a solution to overfishing. However, the aquaculture industry repeatedly faces sustainability issues and fails to adhere to environmental regulations that threaten marine health.
The oceans are essential to human health and well-being, feeding billions, supporting millions of jobs, and supplying medicinal materials. However, environmental contaminants like pesticides have profound impact on the ecosystem and the inhabitants. Therefore, it is necessary to understand how pesticides can influence resistance among lethal pest populations, especially in ecologically vulnerable and highly interconnected ecosystems like ocean basins. The authors of the report caution, “These results demonstrate the speed to which this parasite can develop widespread multi-resistance, illustrating why the aquaculture industry has repeatedly lost the arms race with this highly problematic parasite.”
Over the past two decades, organophosphate and pyrethroid insecticides have been the two main chemical classes used to control parasitic salmon lice. However, laboratory studies find increasing resistance among salmon lice to these chemicals, in addition to multi-resistance after in vitro crossbreeding. Since laboratory studies identify that multi-resistance to both chemical classes can occur via crossbreeding, researchers suggest this same resistance transpires in the field. Therefore, this study aims to address multi-resistance in salmon lice populations resulting from reduced sensitivity to multiple chemical compounds in the North Atlantic region.
From 2000 to 2017, researchers sampled 1,988 lice from North-Eastern wild Atlantic salmonid (salmon, sea trout, and farmed salmon) populations. Researchers analyzed parasites for genetic markers for both pyrethroid and organophosphate resistance.
The study results find genetic resistance among salmon lice has a spatiotemporal (location and time) evolutionary pattern. This pattern means that lice demonstrate simultaneous resistance to organophosphate and pyrethroid insecticides across the entire North Atlantic, except Canada. Over 50 percent of lice populations around fish-farming operations are resistant to both insecticide classes. Some sample areas contain lice populations that are all resistant to at least one pesticide. Researchers infer aquaculture intensive regions, using an extensive amount of chemicals for delousing, leads to pesticide multi-resistance among salmon lice populations.
The U.S. Department of Agriculture (USDA) defines aquaculture as any “farming of aquatic organisms, including baitfish, crustaceans, food fish, mollusks, ornamental fish, sport or game fish, and other aquaculture products.” Farmed fish, like Atlantic salmon, in this case, use one of the most high-risk aquaculture practices, open-net pens in coastal and offshore regions. These pens allow easy exchange of waste (i.e., feces), chemicals (i.e., pesticides and pharmaceuticals), parasites/diseases (i.e., sea lice) between farm and surrounding ocean environment. The discharge of waste, chemicals, and parasites/diseases can have a disastrous impact on marine organisms and plants, disrupting ecosystem services. Many of these pens are in relatively remote areas, somewhat “hidden” from public scrutiny. However, these fish live in very crowded conditions, unlike wild-caught fish. The fish consume food that may contain various pharmaceuticals or insecticides to control diseases and pest infestations that frequently occur in these conditions. Furthermore, the farm pens can attract predators, such as marine mammals, that can tangle and drown in fish farm nets.
This study is one of the first to demonstrate spatiotemporal resistance to multiple chemical pesticides among salmon lice under real-world conditions. According to the results, specific sampling years in combination with geography highlight how resistance spreads. Under normal conditions, lice populations decline in the winter with a shift in salmonid population dispersal. However, the crammed, over-treated nature of farm fishing creates an environment for these parasites to persist through regular winter die-offs. Resistant lice appear in farm pens a few years post-treatment and leak via current through the barrier, due to their small size. All oceans connect to one another, cycling nutrients, chemicals, and organisms throughout the world. Hence, pesticide-resistant lice can potentially spread their resistance gene across the entire ocean basin. These mutant parasites have already made their way from Scandinavia to Greenland and Iceland, where farmers never used chemical pesticides.
There are similar reports about the adverse effects of farmed fish on Scotland’s west coast and Northern Isles. The use of antibiotics and pesticides on local marine ecosystems (i.e., insecticides to control sea lice in farmed salmon) results in coastal habitat loss and genetic and health risks to wild marine populations. Marine species biodiversity is already rapidly declining due to overfishing, global warming, pathogens, and pollution. This biodiversity loss may result in changes in marine and terrestrial ecosystem function and reduce ecosystem services.
Salmon lice are the greatest challenge to aquaculture production and environmentally sustainable aquaculture. These parasites attach to the fish’s skin and feed on their blood and mucus, creating sores that lead to infection or death. Thus, investigating the ubiquity and distribution of pesticide multi-resistance among sea lice populations in the North Atlantic is critical. Pesticides are pervasive in all water ecosystems—from rivers, lakes, and oceans to glaciers in the Arctic. Therefore, it is essential to understand how parasites may develop resistance to pesticides used to control populations to safeguard human, animal, and environmental health.
Advocates say that the federal government should require safeguards in aquaculture industry practices to avoid harmful impacts on wild marine organisms, water resources, and aquatic habitats. A sustainable aquaculture industry, according to the Monterey Bay Aquarium’s Seafood Watch program, would require robust and timely production data, prohibit the discharge of wastes over certain environmentally determined levels, and specify appropriate siting locations for such operations. Instead, federal policy has opted, as the Center for American Progress says, to “focus on weakening successful fisheries management measures and selling off federal waters to big corporations with few safeguards.”
Regulation and elimination of pesticides, not only in aquaculture but in agriculture and other areas of use, can reduce the propagation of harmful effects on the wildlife, ecosystem, and health. Furthermore, melting glaciers associated with the climate crisis elevates new concern over the high levels of chemical concentrations in the oceans from pesticides trapped in ice. Toxic pesticide use must end to protect the nation’s and world’s waterways and reduce the number of pesticides and resistant parasites found in our food, water, and wildlife resources. Learn more about pesticide’s hazards to wildlife and what you can do through Beyond Pesticides’ wildlife program page.
There are many resources individuals can use to help gain knowledge and apply practices to avoid pesticide use and its adverse effects. These include news stories, local organizations, school pesticide policies, regulatory contacts, and least-toxic pest control operators. Organic practices can successfully eliminate toxic pesticide use. Replacing pesticides with organic, nontoxic alternatives is crucial for safeguarding public health and ecosystems from pesticide toxicity. Buying, growing, and supporting organic can help eliminate the extensive use of pesticides in the environment and from your diet. For more information on why organic is the right choice for both consumers and the farmworkers who grow our food, see Beyond Pesticides webpage, Health Benefits of Organic Agriculture.
Help Beyond Pesticides educate and build the movement that will bring long-needed protection to humans, animals, and the entire environment by attending the National Pesticide Forum on June 8 and 15. Cultivating Healthy Communities brings together expert scientists, farmers, policymakers, and activists to discuss strategies to eliminate harms from toxic chemical use in favor of nontoxic organic solutions. The conference began with a pre-conference on May 24, launched on May 25, and continues every Tuesday until June 15, 2021. Registration is open today and available through the webpage on this link. It starts with us. Upon registration, you will be able to view talks from the entire conference.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Royal Society Open Science, New Scientist
