Study of Feeding Behaviors in the Southwest
study detailing the feeding behaviors of four species of fish found in the
Colorado River and its tributaries uncovered a few surprises and opened new
insights to the challenges faced by native fish species in the Southwest (doi: 10.1002/jez.1000).
of the biggest challenges are relatively recent ones. In a diverse region known
for its markers of geologic time, a combination of dam building and the
introduction of nonnative species have dramatically reduced the survival
chances of native fish, said Alice Gibb,
NAU biology professor. In her study,
Gibb and her colleagues compared the native roundtail chub with the nonnative
smallmouth bass, and the native Sonora sucker with the nonnative common
carp—species that occupy the same “ecological niche.”
Gibb expected the nonnatives to consume everything offered to them, the study
found that it was the native fish that had a broad diet in the lab. The
nonnatives were choosier. “I would
interpret the native feeding as opportunistic behavior,” Gibb said, adding that the nonnatives are from more stable
and clearer conditions—just like those created by the introduction of dams.
Gibb also noted that the nonnatives have bigger mouths. “That’s going to provide an advantage, especially when it comes to eating other fish,” she said. Smallmouth bass, for example, can eat chub—but not the other way around—and they have a better chance of doing so in clear water.
“The research results suggest that the conditions favor the nonnatives,” Gibb said. Considering that those conditions are human caused, the findings have implications for wildlife management. “You can try to extirpate the nonnatives,” Gibb said, noting an environmental restoration of Fossil Creek that has created a reservoir habitat for native fish. “But people want their sport fish, which are good predators in clear conditions.”
Such dynamics are not the case only in the Southwest. Gibb said there is growing worldwide interest in a field known as “invasion ecology.” “It’s an area that’s recently been recognized as a tool to understand why some species go extinct and others take over.”
--Adapted from “Inside NAU”