Fisheries Collapse in Japanese Lake Linked to Pesticide Use

Yomegashima Island on Lake Shinji, Matsue, Shimane Prefecture, Japan. (Bernard Gagnon via Wikipedia)

(CN) – The 1993 collapse of two fisheries in a Japanese lake could have been caused by neonicotinoids, the most widely used class of pesticides on the planet, scientists announced Thursday.

Neonicotinoids are addictive and largely responsible for the precipitous decline in the bee population. The pesticides are popular due to their ability to absorb into the soil and become part of the plant, but their success has led to harm to species and in some case the devastation of food webs. In fact, they have been proven to make white-crowned sparrows lethargic from ingesting trace amounts in seeds, in turn affecting their population growth.

The class of pesticides may also be to blame for the sudden devastation of these fisheries on Lake Shinji, Japan. In their study published Thursday in the journal Science, lead author Masumi Yamamuro and his colleagues used more than two decades of data gathered on the lake’s chemistry, biology, and fishery yields to track the exact impact of neonicotinoid use. Specifically, the researchers studied how the chemicals affected the zooplankton, smelt, and eel.

Analysis of this data showed a shocking decrease in the zooplankton springtime biomass: 83% after the first application of the neonicotinoid pesticide. In turn, the populations of species in the fishery that fed on the zooplankton abruptly collapsed. The smelt harvest plummeted from 240 tons to 22 tons just one year after the first use of neonicotinoids.

In short, the neonicotinoids decreased the abundance of invertebrates eaten by smelt and eel, leading to the collapse of the fisheries. The authors say the sharp decline in zooplankton cannot be explained by other common factors such as nutrient depletion or changes in salinity or oxygen concentration.

The authors argue these results indicate other fishery declines in Japanese lakes could have been caused by food web disruption from neonicotinoid use. They note that due to its widespread use, neonicotinoids are likely having the same effects in bodies of water globally, which is cause for concern.

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