Colonial dams changed predator and prey in Connecticut lakes

New England colonists didn’t plan to create an evolution laboratory when they dammed the region’s waterways, but these man-made barriers have spurred pronounced changes in both predator fish and the prey they eat, a Yale-led research team has found.

The prey fish alewife, in response to changes in their food sources, have become dramatically smaller and remain in open water more in landlocked lakes compared to alewife that return to the sea to spawn, according to research by the lab of Yale’s David Post, professor of ecology and evolutionary biology. Changes in the alewife have also triggered behavioral and body changes in the chain pickerel, a predator fish that normally prowls the shores on region’s lakes, according to a new survey of 12 regional lakes published Sept. 14 in the journal Nature Communications. 

Some pickerel in landlocked lakes with alewife have moved out from the shoreline to the center of lakes where alewife congregate. These pickerel have more fat and slightly larger bodies that make them more efficient swimmers, and thinner heads, perhaps because their prey has become smaller.

“This suggests these pickerel are becoming alewife specialists,” Post said.

These changes in the pickerel are not seen in lakes with access to the sea or in lakes lacking alewife, the researchers found.

“These lakes are a perfect laboratory to study how ecological and evolutionary processes interact in human time scales,” Post said.  “These aren’t changes that happened a million years ago.”

Lead author of the paper is Jakob Broderson, former postdoctoral researcher in Post’s lab and now at EAWAG Swiss Federal Institute of Aquatic Science and Technology. Jennifer Howeth, also a former postdoctoral researcher now at the University of Alabama, is the third author.

(Illustration by Patrick Lynch.)