Identification of Bighead Carp and Silver Carp early-life environments and inferring Lock and Dam 19 passage in the Upper Mississippi River: insights from otolith chemistry

Abstract

Knowledge of environments used during early life history and movement patterns of Bighead Carp (Hypophthalmichthys nobilis) and Silver Carp (H. molitrix), collectively termed bigheaded carps, in the Upper Mississippi River (UMR) would be valuable for informing control measures to limit further population expansion and impacts of these species. Lock and Dam 19 (LD19) is a high-head dam on the UMR that delineates downriver areas where bigheaded carps are well established from upriver pools where these species are less abundant and evidence of reproduction and recruitment are limited. Principal natal environments supporting recruitment of emerging bigheaded carp populations in the UMR are unknown. The objectives of this study were to (1) infer environments occupied during early-life stages by bigheaded carps collected in UMR Pools 19-21 during 2013-2014 using otolith microchemistry and stable isotope analyses, and (2) use early-life environment assignments and capture location to identify individuals that passed through LD19. Differences in multivariate water chemistry signatures (Sr:Ca, Ba:Ca and δ18O) among the UMR, its tributaries, and the Missouri and Middle Mississippi rivers enabled development of a classification model for inferring early-life environment of bigheaded carps. Multiple sources of recruits, including from tributaries, have contributed to upriver expansion of bigheaded carps in the UMR. Sustainable control of bigheaded carps upstream of LD19 will likely require efforts to control local recruitment and immigration from downriver. The frequency of bigheaded carps collected in Pool 19 that were downstream of LD19 during early life suggests that bigheaded carps upstream of LD19 still predominantly consisted of immigrants from downriver during 2013-2014. Otolith chemistry provides an approach for assessing the extent to which changes in abundance of bigheaded carps upstream of LD19 are associated with local recruitment or immigration from downriver.

A Comparison of Grass Carp Population Characteristics Upstream and Downstream of Lock and Dam 19 of the Upper Mississippi River

“…However, large tributaries of the UMR, such as the Des Moines, Skunk, Iowa, and Cedar rivers, offer long stretches of free-flowing river where Grass Carp reproduction has occurred (Camacho 2016), likely leading to the more consistent recruitment patterns in our study. In addition, the migratory abilities of Grass Carp (Gorbach and Krykhtin 1988) indicate that migrants from more consistently recruiting populations downstream of LD19 (e.g., Larson et al 2017) could supply a few recruits periodically, similar to other invasive carp (e.g., Whitledge et al 2019). Placement of deterrents within the navigation locks at LD19 are being considered to reduce migration of invasive carps and propagule pressures upstream (e.g., Donaldson et al 2016).…”

“…In areas such as the dammed UMR, these higher velocity river sections are more common immediately downstream of dams, particularly LD19 where spawning of Grass Carp and other invasive carp has been documented to occur (Camacho 2016). Thus, LD19 is considered a key choke point (i.e., limited movement upstream and quality spawning habitat downstream where fish congregate) for invasive carp population management in the main stem UMR (e.g., Larson et al 2017;Whitledge et al 2019).…”

Natal environments of age‐0 paddlefish in the middle Mississippi River inferred from dentary microchemistry

“…Water samples were taken from the MMR and tributaries used in this study for strontium (Sr) and calcium (Ca) concentrations to characterize Sr:Ca signatures for each river. Other natural markers commonly used in studies of fish hard‐part microchemistry (e.g., Ba:Ca, Mg:Ca, Mn:Ca, and 87 Sr/ 86 Sr) were not used in this study, as they either do not differ among rivers considered to be potential natal locations for age‐0 paddlefish in the MMR or do not provide additional capability of distinguishing among rivers that differ in water Sr:Ca (Zeigler & Whitledge, ; Whitledge et al, ). Water samples were collected monthly during mid‐June to mid‐October 2006 through 2016 to verify persistence of differences in Sr:Ca signatures of the MMR, MOR, and tributaries.…”

“…The 5th and 95th percentile values of water Sr:Ca for each river were then entered into the regression relating water and dentary bone Sr:Ca (Bock, Whitledge, Pracheil, & Bailey, ) and 95% confidence limits around predicted dentary Sr:Ca values were calculated. The 95% confidence limits around predicted dentary Sr:Ca were used as thresholds that defined the upper and lower limits of expected dentary bone Sr:Ca for each river (Laughlin, Whitledge, Oliver, & Rude, ; Whitledge et al, ). Predicted ranges of dentary bone Sr:Ca for each potential natal river within the study area were used to interpret dentary bone Sr:Ca data from age‐0 paddlefish collected in the MMR; dentary Sr:Ca values that fell within the predicted range for a particular river were considered indicative of the fish having occupied that river at the time that portion of the dentary bone was grown.…”

“…Microchemical analyses of fish hard‐part structures have been used to identify recruitment sources and reconstruct environmental histories of fish (Bock, Whitledge, Pracheil, & Bailey, ; Kennedy, Klaue, Blum, Folt, & Nislow, ; Smith & Whitledge, ), including large river specialist species (Laughlin, Whitledge, Oliver, & Rude, ; Porreca et al, ). Large rivers and their tributaries often have distinct elemental signatures (Abell, Oliver, & Whitledge, ; Laughlin, Whitledge, Oliver, & Rude, ; Whitledge et al, ; Wuellner, Grote, & Fincel, ; Zeigler & Whitledge, , ), and the hard‐part elemental signature reflects the water in which they reside (Bock, Whitledge, Pracheil, & Bailey, ; Kennedy, Klaue, Blum, Folt, & Nislow, ; Smith & Whitledge, ). For example, Laughlin, Whitledge, Oliver, and Rude () used otolith microchemistry analyses to determine that blue catfish Ictalurus furcatus and channel catfish I .…”