April 11, 2023
Freshwater Research Institute finds that water temperatures affect certain behaviors in a cold-water predator, especially when in the presence of one that prefers warmer waters.Recent research from Susquehanna University’s
“Brook trout are considered an apex predator in cold-water streams,” said Matt Wilson, director of the FRI and SU’s Center for Environmental Education and Research. “As temperature increases, it causes them to exhibit a weaker top-down control on other species and this could lead to cascading ecosystem effects.”
To examine the influences of temperature on competitive interactions between brook trout and creek chub, Wilson, Matt Persons, professor of biology, and Bryan Colby ’20 observed feeding behavior and aggression at three temperatures (64°F, 68°F and 72°F) in special tanks that were built by SU students.
Wilson and Colby replicated a stream system in four 900-liter tanks where different pairings of fish were housed. Fish were fed with food pellets and provided with pebble and gravel substrate and a cinderblock that the fish were able to use for cover.
“As temperatures increased, the number of pellets eaten in brook trout pairings decreased, while the number of pellets eaten in creek chub pairings increased,” Wilson said.
Brook trout pairs also showed fewer aggressive behaviors, such as bumping and chasing, at increased temperatures. In contrast, average bumps and chases in creek chub pairs increased at higher temperatures. And the average bumps and chases in trout-chub pairs were significantly greater than either previous pairings, even at the highest temperature.
“We found both species and temperature significantly affected the feeding behavior and aggressive interactions among fish pairings,” Persons said. “Brook trout feeding rates and aggression decreased with increasing water temperatures when in the presence of a more thermally tolerant competitor, in this case the creek chub. And we saw the opposite for the creek chub.”
Wilson said their research has implications for all cold-water stream ecosystems.
“As stream temperatures continue to warm and competitive interactions change, brook trout could be pushed out of their historic habitats,” Wilson said. “This warming will likely also cause competitive mismatches between many other species, which can lead to the consumption of different macroinvertebrates, increased algal growth and shifts in emerging insect communities.”