This past year, Dr. Isaac Ligocki, an NSF post-doctoral fellow with Dr. Rebecca Calisi here at UC Davis, set out to do field work in Northern California. He aimed to examine the effects of a common group of pesticides: the pyrethroids—deemed “safe” alternatives for agricultural use. Widely used in the California Central Valley, these chemicals run off soil from farms and field and end up in our natural waterways. Other supposedly “safe” pesticides, such as atrazine or glyphosate, have been found to negatively affect aquatic animals, such as frogs and fish. These effects can be drastic, with frogs shown to have “hermaphrodite” characteristics, or reproductive traits of both males and females after exposure to atrazine. These chemicals cause these problems by interrupting the normal signals of the body: hormones. With his background in fish field work, Isaac set out to find out what effects pyrethroid pesticides might have on the brains and reproductive biology of a common fish, the Western mosquitofish (Gambusia affins).

Isaac’s field sites promised to be in some of the most beautiful corners of Northern California. He had planned to sample water from sites spanning the Sacramento River delta, east Bay Area, and north and south Central Valley (California’s agricultural hub). He and his team set out for two sampling seasons: one in the winter, when rains pulled out pesticide residues from the soil, and another in the summer. However, heavy winter rains quickly foiled his plans. Although California needed the rain, a few of his field sites were quickly submerged in water! Plans to go out sampling in January were quickly postponed… until April, when even after four months, the river had run so high that one of his sites—the Consumnes River Preserve—was still flooded over!

However, Isaac and team decided to push ahead with their timeline. Equipped with a high-wheeled pick-up truck, waders, and an intrepid team, Isaac was able to sample fish at the park anyway. Their perseverance went well rewarded – it turned out that the little mosquitofish seemed to flock to the flooded parking lot! They were easily able to get hundreds of fish within minutes of netting, a task that often took a few hours of patience at other sites. Isaac suspects the fish preferred the refuge from predators that the shallow parking lot puddles offered, but wonders why an opportunistic heron didn’t take advantage…

Now, in the lab, Isaac has paired his field work with a controlled study looking at the effects of specific doses of pyrethroid pesticides – bifenthrin or cyfluthrin – on captive female mosquitofish. He and his team have been examining its effects on mate choice, social behavior, and gene expression in the brain and liver. By comparing work done in the field, where the world is more complex than one specific dose of pesticide, Isaac can predict and compare effects the pesticides measured in actual aquatic ecosystems might have on the fish that live in our local watersheds.

As fish researchers, Isaac and company aren’t afraid of getting wet, and came equipped with waders, boots, and life jackets. But field workers everywhere be warned: climate change is real and brings unpredictable weather with it. It might be worth packing an extra pair of boots (and a net) to prepare for any fiasco – or opportunity – when it strikes!

Dr. Isaac Ligocki is currently a post-doctoral fellow in Dr. Rebecca Calisi’s lab at UC Davis. Before coming to California, he received his PhD from The Ohio State University studying social dynamics in a cooperatively breeding cichlid fish species in Lake Tanganyika. To read more about Isaac’s work, past and current, visit his website here: https://isaacligocki.com/

[By: Victoria Farrar]