Sources of Nonnative Centrarchids in the Upper Colorado River Revealed by Stable Isotope and Microchemical Analyses of Otoliths

Abstract

Nonnative fishes represent a significant impediment to the recovery of imperiled fishes, including those endemic to the Colorado River in the southwestern United States. Efforts to control nonindigenous fish abundance in the upper Colorado River basin have been unsuccessful owing in part to lack of knowledge regarding nonnative fish recruitment sources. We determined the source habitat (floodplain pond versus riverine habitats) for nonnative centrarchid fishes (largemouth bass Micropterus salmoides, green sunfish Lepomis cyanellus, bluegill L. macrochirus, and black crappie Pomoxis nigromaculatus) in the upper Colorado River using stable hydrogen isotopic composition (δD) and strontium: Calcium (Sr: Ca) ratios in fish otoliths as natural markers of environmental history. Stable hydrogen isotope analysis revealed that 59% of centrarchids exhibited the otolith core signatures expected for riverine‐origin fish, while 22% had emigrated from floodplain ponds and 19% were of uncertain origin. Strontium: Calcium ratio data were consistent with the δD assays and indicated that relatively few fish immigrated to the river from high‐salinity habitats. Black crappie was the only species that originated primarily from floodplain ponds. Efforts to control the abundance of most of the fishes included in this study should be concentrated in riverine habitats given the hydrologic conditions (below‐average river discharge) present during our study. However, the proportion of pond‐origin fish increased with fish age, which, coupled with historical river discharge data, suggested that floodplain pond contributions to riverine nonnative fish populations fluctuate with the interannual variations in flow regime and river‐pond connectivity. Our results are the first to demonstrate the utility of δD as a natural marker of fish environmental history that will probably provide valuable insights into the management of fish in other environments.

Otolith trace element and stable isotopic compositions differentiate fishes from the Middle Mississippi River, its tributaries, and floodplain lakes

“…Distinct water  18 O signatures of floodplain lakes and the Mississippi River are likely due primarily to the greater opportunity for evaporative fractionation (Hoefs, 2004) to be expressed in floodplain lakes as a result of their longer water residence times compared to the river. Whitledge et al (2007) observed similar differences in water hydrogen isotopic composition (δ 2 H, which undergoes similar fractionation processes in the hydrologic cycle) between floodplain ponds and the upper Colorado River due to higher evaporation rates of pond water. Persistent differences in water  18 O between the Illinois River and its floodplain lakes have also been documented (Zeigler & Whitledge, 2010).…”

“…Most classification errors occurred among fish collected from small tributaries of the Mississippi River, although some of these individuals were misidentified as having been locations (Gao et al, 2001;Wells et al, 2003;Brazner et al, 2004;Bickford and Hannigan, 2005;Dufour et al, 2005;Whitledge et al, 2007;Whitledge, 2009). …”

“…Application of otolith trace element and isotopic compositions as natural tags has emerged as an effective technique for addressing questions regarding environmental history of freshwater fishes (e.g., Wells et al, 2003;Brazner et al, 2004;Dufour et al, 2005;Munro et al, 2005;Feyrer et al, 2007;Whitledge et al, 2007;Schaffler & Winkelman, 2008). Trace element and stable isotopic compositions of otoliths often reflect those of environments occupied by a fish (e.g., Kennedy et al, 2002;Wells et al, 2003;Dufour et al, 2005;Whitledge et al, 2006) and are unaltered metabolically following deposition (Campana & Thorrold, 2001).…”

Recruitment sources of invasive Bighead carp (Hypopthalmichthys nobilis) and Silver carp (H. molitrix) inhabiting the Illinois River

“…Trace element and stable isotopic compositions of otoliths have been used as natural markers of environmental history for individual fishes in a variety of freshwater environments (Wells et al 2003;Dufour et al 2005;Munro et al 2005;Whitledge et al 2007;Whitledge 2010, 2011;Chapman et al 2013), and represent a potential approach to identify natal environment and larval and juvenile nursery habitats of Bighead Carp and Silver Carp in the Illinois River. Otoliths are calcareous concretions in the inner ear of fishes that contain a permanent record of age and growth and are metabolically inert (Campana and Thorrold 2001).…”

“…Association of otolith biochronology with isotopic or elemental composition enables retrospective description of fish environmental history (e.g., identification of natal environment from the portion of the otolith accreted during early life) when an individual has resided in chemically distinct locations for a period of time sufficient to incorporate the signature of those sites (Kennedy et al 2002;Dufour et al 2005;Whitledge et al 2007). Only a few published studies have used otolith chemistry to identify natal environment of invasive fishes in large floodplain river systems.…”