Fish exposure to pesticides impacts their behavior in current and future generations

Recent research has uncovered startling effects of pesticide exposure on fish, revealing both immediate behavioral changes and lasting impacts that extend to their offspring, who themselves have never been directly exposed to these chemicals.

This study, spearheaded by co-author Susanne Brander, an ecotoxicologist at Oregon State University’s Hatfield Marine Science Center, highlights a concerning trend that could have broader implications for all vertebrates, including humans.

Pesticide peril ripples through fish generations

The research focused on fish exposed to common pyrethroid pesticides — bifenthrin, cyfluthrin, and cyhalothrin — known for their neurotoxicity and prevalence in waterways, particularly in the San Francisco Bay and Sacramento-Joaquin Delta.

These chemicals are not isolated to agricultural settings but are also widespread in residential areas, posing a risk to a wide array of aquatic life and potentially to human health due to runoff from populated areas.

“This exposure is happening not just to these fish, but to all aquatic organisms in areas that are receiving runoff from areas populated by humans,” Brander said.

“It’s safe to say that we’re seeing influences at the population level if fish that were exposed for a few days as embryos and larvae are then producing offspring that are developmentally deformed, or males that are not able to produce as much sperm.”

Adding to the concern is the role of climate change in expanding the habitats of various insect species, necessitating increased pesticide use and thereby exposing even more organisms to these harmful chemicals.

Echoes of pesticide exposure seen in behavior

The study utilized inland silversides, a model species for North American estuaries, exposing silverside fish embryos to extremely low concentrations of these pesticides.

The amount used for exposure was likened to a teaspoon of pesticide in an Olympic-sized swimming pool, emphasizing the low concentration required to observe effects.

Following exposure, the fish showed hypoactive behavior, potentially diminishing their ability to seek food. Remarkably, the offspring of these exposed fish exhibited hyperactive behavior, suggesting a compensatory mechanism for the parents’ reduced activity.

Additionally, adult males exposed as larvae displayed reduced gonad size, whereas their offspring showed increased fecundity, indicating varied reproductive impacts across generations.

Extrapolating the fish data to human populations

Brander emphasizes the broader implications of these findings, noting the genetic similarities between many fish species and humans.

“This study is another demonstration of how early-life exposure to these chemicals can affect fish for months and, in the case of humans, for potentially years,” Brander said.

“We could potentially use this as a model for how human babies or humans in utero could respond to these chemicals — fish use the same hormone receptors as we do; the same steroids. So something that interferes with reproduction in fish could potentially have the same effect on humans.”

The adaptation observed in the fish to their pesticide exposure, while a testament to their resilience, also hints at possible overcompensation.

This could detract from other vital biological functions, such as growth or predation, suggesting that the impacts of such exposure are complex and multifaceted.

Brander concludes with a call to action on environmental regulation, stating, “In terms of environmental regulation, if we put stricter controls into effect because of studies like this, it’s going to take a few generations of fish — or whatever the organism is — for them to completely recover,” she said.

Awareness to action: Protecting fish from pesticides

In summary, this disturbing study highlights the profound and lasting effects that even minimal pesticide exposure can have on fish and their offspring, illuminating a path forward that necessitates stricter environmental regulations to safeguard aquatic ecosystems and, by extension, human health.

By demonstrating the intergenerational impact of pesticides, Susanne Brander’s research calls for immediate action to reduce chemical runoff into our waterways.

Her results also emphasize the interconnectedness of all vertebrate life, urging a reevaluation of our reliance on harmful pesticides.

As we face the dual challenges of climate change and biodiversity loss, the findings serve as a critical reminder of the urgency to protect our environment and ensure a healthy planet for future generations.

The full study was published in the journal Environmental Science & Technology.

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