Stable isotope signatures of native and nonnative fishes in Upper ColoradoRiver backwaters and ponds.

摘要

Naturally-occurring stable isotopes of carbon (C-13) and nitrogen (N-15) were analyzed to address questions about trophic interactions among native and normative fishes in the upper Colorado River basin, and to begin to evaluate the discreteness of floodplain pond fish assemblages. Specifically, 2 hypotheses were evaluated: 1) can stable isotope analysis be used to establish trophic relationships among native and nonnative fishes, and 2) can stable isotope signatures be used as a naturally-occurring marker to identify, river fishes that have migrated from floodplain ponds Nitrogen isotope ratios showed that at a particular location, either in ponds or backwaters, centrarchids were usually the top predators in each system. In one backwater, delta N-15 and delta C-13 signatures of the fish assemblage ranged about 4 parts per thousand. The number of trophic levels represented was Limited to about 2, and variation in carbon sources appeared to be great. The native flannel-mouth sticker, Catostomus latipinnis, was most distinct with a relatively low delta N-15 and high delta C-13 signature. Stable isotope signatures appeared to have utility as a naturally occurring marker for tracking influx of normative fishes to the Colorado River from ponds. Whereas pond signatures were not consistently depleted or enriched relative to those from backwaters, mean stable isotope signatures were more different among ponds than among backwater sites. Further, within particular species, some ponds had carbon or nitrogen signatures that were quite different from those at backwater sites. Stable isotope analysis appears to have promise for studying trophic relationships and movement patterns of native and normative fishes in the upper Colorado River basin.