麻豆淫院

(麻豆淫院Org.com) -- A 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.

Some 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 Northern Arizona University researcher Alice Gibb.

A biology professor, Gibb is the corresponding author of a new paper, 鈥淧rey Capture Behavior of Native vs. Nonnative Fishes: A Case Study from the Colorado River Drainage Basin (USA),鈥� that appears in the Journal of Experimental Zoology A.

That native fish in the Southwest are on the decline is not in dispute, but the research provides more evidence as to why.

鈥淲e altered the habitat native fish evolved for and put in fish that are better-adapted to the new conditions,鈥� Gibb said, calling the changes a 鈥渙ne-two punch鈥� for native fish.

For the 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鈥攕pecies that occupy the same 鈥渆cological niche.鈥�

While 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.

鈥淚 would interpret the native feeding as opportunistic behavior,鈥� Gibb said. But it鈥檚 a behavior that evolved in the constantly changing habitat of the Southwest in warm, turbid water. The nonnatives, Gibb said, are from more stable and clear conditions鈥攋ust like those created by the introduction of dams.

Gibb also noted that the nonnatives have bigger mouths. 鈥淭hat鈥檚 going to provide an advantage, especially when it comes to eating other fish,鈥� she said. Smallmouth bass, for example, can eat chub鈥攂ut not the other way around鈥攁nd they have a better chance of doing so in clear water.

鈥淭he research results suggest that it鈥檚 the conditions that favor the nonnatives,鈥� Gibb said.

Considering that those conditions are human caused, the findings have implications for wildlife management.

鈥淵ou can try to extirpate the nonnatives,鈥� Gibb said, noting an environmental restoration of Fossil Creek that has created a reservoir habitat for native fish. 鈥淏ut people want their sport fish, which are good predators in clear conditions.鈥�  

Such dynamics are not the case only in the Southwest. Gibb said there is growing worldwide interest in a field known as 鈥渋nvasion ecology.鈥�

鈥淚t鈥檚 an area that鈥檚 recently been recognized as a tool to understand why some species go extinct and others take over.鈥�