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James T. Lamer

Publications and source records attributed to James T. Lamer.

15 recordsLinked to original sources
USGS2026

Life history traits and population dynamics of Freshwater Drum across large river gradients

Objective Monitoring and assessment of nongame native fishes is limited, but conservation interest in these species is growing. Freshwater Drum Aplodinotus grunniens are a wide-ranging species that serve important functional roles and could serve as an indicator for similar but less common species. Our overall objectives were to quantify and compare population dynamic rates and life history of Freshwater Drum among study reaches in the upper Mississippi and Illinois rivers and relate these metrics to hypothesized environmental and anthropogenic factors. Methods We integrated recently collected age data with monitoring data to estimate age and size distributions, growth curves, maturation schedules, mortality rates, and young-to-adult ratios of Freshwater Drum in six study reaches spanning 1,500 km of river. Principal component analyses and linear regression were used to relate environmental and anthropogenic gradients (latitude, commercial harvest, hydrologic dynamics, primary productivity) to life history traits and population dynamic rates. Results We found latitudinal gradients in life history traits and population dynamic rates whereby Freshwater Drum in upstream, higher-latitude study reaches generally exhibited later maturity, slower growth, smaller maximum size, and lower mortality rates compared with those in lower-latitude study reaches. Further, young-to-adult ratios positively corresponded with chlorophyll- a concentration. No clear relationships were apparent between population dynamic rates and hydrologic variation or commercial harvest. Conclusions Latitude is an important structuring component of life history traits and population dynamics of Freshwater Drum in the upper Mississippi and Illinois rivers likely due to both temperature seasonality and disturbance regimes. The presence of demographic structure in a widespread, common species such as Freshwater Drum suggests similar patterns likely exist in other long-lived native fishes.

Illinois, Iowa, Minnesota, Missouri, Wisconsin↗
USGS2025

Big River bluegill: Combining vital rates and long-term monitoring to understand population dynamics in large rivers

Long-term monitoring indicates bluegill catch rates are relatively stable in some reaches of the Upper Mississippi River and highly variable in others, whereas in the Illinois River, catch rates have decreased. A lack of age structure information precludes understanding population processes responsible for patterns in catch rates. To build a better understanding of why catch rates have changed over time, we integrated short-term age structure information with long-term monitoring data to quantify and assess spatial patterns in bluegill population dynamics across six study reaches of these two rivers. Specifically, we estimated and compared age and size structure, growth, maturity, mortality, and recruitment. We used quantile regressions to apply age estimates to long-term data for investigating trends in age-based catch rates reflective of recruitment (age-1 catch rates), mortality (using age-1 and age-2+ catch rates), and spawning stock (age-2+). Our findings indicate trends in bluegill age-2+ catch rates increased and then stabilized across upstream study reaches, but dynamic rates, size structure, and age at maturity varied among reaches. Bluegill populations in downstream study reaches had low maximum size, early maturation, low mean age, low proportional stock density, declining recruitment, and declining age-2+ catch rates. An insufficient number of bluegills were collected from the study reach furthest downstream to adequately quantify dynamic rates. Our results support life history theory in that bluegill respond to unstable environmental conditions through life history adaptations. These findings show how integrating periodic age structure information with long-term monitoring can enhance population assessments.

Illinois, Iowa, Minnesota, Missouri, Wisconsin↗
USGS2024

Flooding and dam operations facilitate rapid upstream migrations of native and invasive fish species on a regulated large river

Dams commonly restrict fish movements in large rivers but can also help curtail the spread of invasive species, such as invasive bigheaded carps ( Hypophthalmichthys spp). To determine how dams in the upper Mississippi River (UMR) affect large-scale invasive and native fish migrations, we tracked American paddlefish ( Polyodon spathula ) and bigheaded carp across > 600 river km (rkm) and 16 navigation locks and dams (LD) of the UMR during 2 years with contrasting water levels. In 2022, a low-water year, both native paddlefish and invasive bigheaded carp had low passage rates (4% and 0.6% respectively) through LD15, a movement bottleneck being studied for invasive carp control. In contrast, flooding in 2023 led to open-river conditions across multiple dams simultaneously, allowing 53% of paddlefish and 46% of bigheaded carp detected in Pool 16 to move upstream through LD15. Bigheaded carp passed upstream through LD15 rapidly (μ = 32 rkm per day) a maximum of 381 rkm, whereas paddlefish moved an average of 9 upstream rkm per day (maximum of 337 rkm). Our results can inform managers examining trade-offs between actions that enhance native fish passage or deter movements of invasive species. This understanding is critical because current climate change models project increases in flooding events like that observed during 2023.

Illinois, Iowa, Minnesota, Wisconsin↗
USGS2024

Smallmouth buffalo (Ictiobus bubalus Rafinesque) population trends and demographics in the Upper Mississippi River System

Smallmouth buffalo ( Ictiobus bubalus Rafinesque) are a large-bodied fish highly valued and commercially exploited across most of their range. Despite this, relatively little is known of their population demographics compared to other exploited species. To fill these knowledge gaps, we analyzed two independent long-term datasets (30 and 57 years, respectively) and population demographic data (age structure, growth, mortality, age at maturity, and recruitment) from multiple pools of the Upper Mississippi River System (UMRS) and Illinois River (Illinois, USA). Long-term data (30-year dataset) generally show downward trends or significant declines in catch per unit effort in the UMRS, while the 57-year dataset shows a stable trend or a significant increase in the Illinois River. The oldest smallmouth buffalo were estimated to be 39 years old, with nearly every pool sampled having individuals estimated to exceed 30 years of age. Except for Pool 13 of the UMRS, 90% of smallmouth buffalo were estimated to mature between 411 and 470 mm in length or between 8.7 and 11.2 years old. Recruitment was variable: strong year classes were generally preceded by multiple years of weak year classes. Our results indicate that the smallmouth buffalo population may be stable in portions of the UMRS and Illinois River systems, but significant declines in the northern extent of the UMRS may warrant conservation concern. Recent research into ages of buffalofishes shows that consideration should be given to the idea that the UMRS population could be age truncated. Results also emphasize the importance of long-term data and the ability to show changes in exploited populations over time.

Illinois, Iowa, Minnesota, Missouri, Wisconsin↗
USGS2024

Upstream experience and experimental translocation of invasive bigheaded carps results in increased upstream passage success at a navigation lock in a large river

Fish movements in regulated rivers can be challenging to study because anthropogenic modifications, such as locks and dams, can influence animal behavior. Upper Mississippi River Lock and Dam 19 (LD 19), for example, is an invasive carp movement bottleneck due to an impassable dam. Upstream fish passage at LD19 is restricted to the lock chamber, making it an optimal location to test invasive fish deterrents that could limit further range expansion. Evaluating the effectiveness of experimental deterrents requires baseline knowledge of fish movements and suitable sample sizes of fish encountering the deterrents to ensure adequate statistical power. Some evidence indicates fish with prior upstream experience may return upstream or challenge potential deterrents at a higher rate than fish without such experience. To test how previous upstream experience could increase the rate at which fish moved upstream through a navigation lock chamber, we compared upstream passage through LD 19 using bigheaded carp captured below the dam (downstream-origin) and two groups of bigheaded carp captured upstream from the dam: those that swam downstream on their own volition (upstream-origin fish) and those that were captured upstream and translocated downstream of LD 19 (translocated upstream-origin). Translocated upstream-origin carp demonstrated the highest rate of upstream passage, with 59% of the fish detected downstream from LD 19 passing upstream during our study. In contrast, downstream-origin carp made no upstream passages over 2 years. Fish origin was shown to influence upstream passage success. This may be an important consideration for fish passage studies and deterrent evaluations.

Illinois, Iowa↗
USGS2024

Reduction of large vessel traffic improves water quality and alters fish habitat-use throughout a large river

Rivers are increasingly used as superhighways for the continental-scale transportation of freight goods, but the ecological impact of large vessel traffic on river ecosystems is difficult to study. Recently, the temporary maintenance closure of lock and dam systems on the Illinois Waterway (USA) brought commercial vessel traffic to a halt along the river's length, offering a rare opportunity to study the response of the ecosystem before, during, and after an extended pause of this persistent anthropogenic disturbance. We observed improvements in main- and side-channel water quality and a redistribution of fish habitat-use during a months-long, near-complete reduction of large vessel traffic. Over 3600 water quality and 1300 fish community samples indicate that large vessel traffic reduction coincided with a 33 % reduction in turbidity as well as increased use of sampling strata near vessel navigation corridors by sound-sensitive and rheophilic fishes. Gizzard shad ( Dorosoma cepedianum ), the most abundant species in the system, also expanded their use of these ‘impact’ areas. Though inland waterway transport is an economically- and climate-friendly alternative to trucking and rail for the shipment of freight, our data suggest that intense vessel traffic may have profound physical and biological impacts across a large river. Monitoring and mitigation of ecological impacts of the ongoing expansion of inland waterway transport around the world will be critical to balancing large rivers as both useful navigation corridors and functional ecosystems.

Illinois↗
USGS2023

Predation of invasive silver carp by native largemouth bass is size-selective in the Illinois River

Silver carp ( Hypophthalmichthys molitrix ) are a nonnative, planktivorous, and highly invasive species of cyprinid located throughout the Mississippi River Basin. Although they co-occur with largemouth bass ( Micropterus nigricans ), an abundant native predatory fish, their predator–prey relationship is poorly understood. This potential relationship warrants investigation as largemouth bass are large-gaped predators capable of exhibiting top-down control on planktivorous fishes. The objectives of this study were to determine if largemouth bass consume juvenile silver carp, and if there was a relationship between length of largemouth bass and length of silver carp consumed. Largemouth bass were collected from the La Grange Pool of the Illinois River using 60 Hz-pulsed DC electrofishing and their diets were analyzed (n = 389, total length = 70–578 mm). Evidence of silver carp was present in 18% of diets of largemouth bass that consumed fish. Lengths of consumed silver carp were estimated from the dimensions of their recovered chewing pads or pharyngeal teeth in the stomachs of largemouth bass. A significant relationship between length of largemouth bass and length of silver carp consumed ( p < 0.001, F = 34.63, r 2 = 0.61) was observed. Estimated total lengths of silver carp were 34–101 mm and were recovered from diets of largemouth bass that were 94–262 mm total length. These results indicate enhancement of native largemouth bass populations is unlikely to substantially reduce silver carp populations in the Illinois River or in other waterways where these species co-occur.

Illinois↗
USGS2021

Age-0 Silver Carp otolith microchemistry and microstructure reveal multiple early life environments and protracted spawning in the upper Mississippi River

Silver Carp Hypophthalmichthys molitrix are highly mobile and fecund planktivorous cyprinids that have invaded much of the Mississippi River and are known to alter food webs and compete with native planktivores. In 2016, for the first time, an abundance of age-0 Silver Carp ( n = 12,208; 16–231 mm) were captured at many ( n = 11) sites upstream of Lock and Dam 19 on the upper Mississippi River. Previous reports were of a few individuals at a few locations; however, effort to capture juveniles of this size was likely less in previous years. Determining the origin, frequency, and timing of the reproductive events that led to this large year-class is important for determining control strategies. We used otolith microstructure and microchemistry from age-0 Silver Carp to estimate timing and frequency of spawning and early life environments of these fish. Hatch dates were determined from the lapillus otoliths of 190 age-0 Silver Carp (16–231 mm), and early life environments were identified from otolith microchemistry for 124 of these fish (64–231 mm). Age-0 Silver Carp were collected from Pools 18 and 19 during July–October 2016 by using a variety of sampling gears. We identified 10 cohorts with hatch dates ranging from May to August 2016 and with main-stem Mississippi River (75%) and tributary (23%) early life signatures. Tributary otolith chemistry signatures were present in all cohorts between May and July ( n = 8) but were absent from the August cohorts ( n = 2). Our results indicate that tributaries and small tributary streams, in addition to the main-stem river, play an important role in Silver Carp recruitment in areas near the reproductive front, where management actions (e.g., contract removal and deterrents) are often targeted.

Illinois, Iowa, Missouri↗
USGS2021

Demographic rate variability of Bighead and Silver Carps along an invasion gradient

Invasive Bighead Carp Hypophthalmichthys nobilis and Silver Carp H. molitrix have infested and caused largescale ecological and economic damage to the Illinois, Mississippi, and Ohio rivers. We compiled demographic data from 42,995 fish from 23 pools in the Illinois, Mississippi, and Ohio rivers, which universities and management agencies previously collected as part of management, monitoring, and research activities. We used this data set to test whether demographic rates (length–weight relations including body condition, mortality, growth curves, and female maturity curves) varied among subpopulations across a gradient of invasion status. We found that length–weight relations and growth curves varied among subpopulations, whereas maturity curves did not. Our findings demonstrated spatial variability in demographic rates for Bighead and Silver carp across a broad geographic area in relation to invasion status and river conditions. Herein, we provide general subpopulation management options and present different hypotheses to explain the observed spatial variability in demographic rates.

Illinois, Indiana, Iowa, Kentucky, West Virginia↗
USGS2020

Lock operations influence upstream passages of invasive and native fishes at a Mississippi River high-head dam

Asian carps continue to expand their range in North America, necessitating efforts to limit the spread and establishment of reproducing populations. Mississippi River Lock and Dam 19 is a high-head dam that represents a population ‘pinch-point’ as passage through the lock chamber is the only means by which fishes can complete upstream movement. As such, this location could be a pivotal control point for minimizing the spread of invasive fishes in the Upper Mississippi River and a possible candidate site for installation of deterrent measures. Our objectives were (1) to study the timing (i.e., weekly and diel) and behavior of fishes in the downstream lock approach, (2) evaluate the relation of presence in the downstream lock approach with environmental factors and lock operation, and (3) identify any upstream or downstream passage events through the lock chamber and the relation between these events and the operation of the lock. Acoustic transmitters were surgically implanted into 262 Asian carps and 216 native fishes to monitor fish activity on a telemetry receiver array deployed around and within the lock for 622 days during 2017–2018. One hundred eighty-six telemetered fish were detected in the downstream lock approach. We documented 14 upstream Asian carp passages and 10 upstream native fish passages; these passages coincided with a specific sequence of large vessel lockages. The results of this study advance our understanding of fish presence and behavior at a Mississippi River mainstem lock and dam and inform the development and testing of deterrent systems at this location or at similar pinch-point lock and dams.

Missouri, Iowa, Illinois↗
USGS2020

Influence of a high-head dam as a dispersal barrier to fish community structure of the Upper Mississippi River

In river systems, high‐head dams may increase the distance‐decay of fish community similarity by creating nearly impermeable dispersal barriers to certain species from upstream reaches. Substantial evidence suggests that migratory species are impacted by dams, and most previous studies in stream/river networks have focused on small streams and headwaters. Here, we assess whether a high‐head dam (Lock and Dam 19; LD 19) on a large river, the Upper Mississippi River (UMR), substantially alters fish community structure relative to variability expected to occur independent of the dam's effect as a fish dispersal barrier. Using fish catch per unit effort data, we modelled the distance‐decay function for the UMR fish community and then estimated the similarity that would be expected to occur across LD19 and compared it with measured similarity. Measured similarity in the fish community above and below LD19 was close to the expected value based on the distance‐decay function, suggesting LD19 does not create an abrupt transition in the fish community. Although some migratory fish species no longer occur above LD19 (e.g., skipjack herring, Alosa chrysochloris ), these species do not occur in high abundance below the dam and so do not drive variation in fish community structure. Instead, much of the variation in species structure is driven by the loss/gain of species across the latitudinal gradient. Lock and Dam 19 does not appear to be a clear transition point in the river's fish community, although it may function as a meaningful barrier for particular species (e.g., invasive species) and warrant future attention from a management perspective.

Illinois, Iowa Minnesota, Missouri, Wisconsin↗
USGS2019

Early generation hybrids may drive range expansion of two invasive fishes

1. Introgressive hybridization between two invasive species has the potential to contribute to their invasion success and provide genetic resiliency to rapidly adapt to new environments. Additionally, differences in the behaviour of hybrids may lead to deleterious ecosystem effects that compound any negative impacts of the invading parental species. 2. Invasive silver carp (Hypophthalmichthys molitrix) and bighead carp (H. nobilis) provide an opportunity to evaluate how hybridization may influence the behaviour, dispersal, and spread of an invasive species introgressive complex. In order to investigate the role hybrids may have in the invasion ecology of bigheaded carps, we examined the distribution, movements, and environmental cues for movement of two invasive fishes and their hybrids in the Illinois River (USA). 3. Early generation hybrids (e.g., F1,F2, and first generation backcross individuals) composed a greater proportion of the population at the invasion front where abundances of bigheaded carp were low. A greater proportion of early hybrids passed through dams upstream towards the invasion front than did other hybrids and parental species. 4. The movements and environmental cues for movement of late-generation backcrosses (more genetically similar to parental genotype) were not different from the parental species with which they shared the most alleles. Although the direction of the relationship between movement and environment was sometimes different for the parental species and associated advanced generation hybrids, these results indicate that management for parental species will also affect most hybrids. 5. Although early generation hybrids are rare, our results indicate they may disperse towards low-density population zones (i.e., invasion fronts) or are produced at greater frequency in low density areas. These rare hybrids have the potential to produce a variety of unique genetic combinations that could result in more rapid adaptation of a non-native population to their invaded range potentially facilitating the establishment of invasive species.

Illinois↗
USGS2017

Using pharyngeal teeth and chewing pads to estimate juvenile Silver Carp total length in the La Grange Reach, Illinois River

The Silver Carp Hypophthalmichthys molitrix is an invasive species in the Mississippi River basin; an understanding of their vulnerability to predation as juveniles may inform control by native predators and predator enhancement (e.g., stocking). Digestion of Silver Carp prey recovered from diets makes it difficult to determine the size‐classes that are most vulnerable to predation by native fishes. The objective of this study was to determine whether the sizes of the chewing pad (CP), pharyngeal teeth (PT), and pharyngeal arch (PA)—the Silver Carp structures most often found intact in predator diets—were predictive of the TL of prey Silver Carp. During 2014 and 2015, juvenile Silver Carp ( n = 136; <180 mm) were collected using 60‐Hz pulsed‐DC electrofishing and mini‐fyke nets in the La Grange reach of the Illinois River. We extracted Silver Carp CPs ( n = 136 fish) and PAs with PT intact ( n = 129 fish) and measured CP length (CP L ) and width (CP W ), eight reproducible PT landmarks (PT1 L –PT4 L ; PT1 W –PT4 W ), and four reproducible PA landmarks (PA1–PA4) to the nearest 0.01 µm. Using simple linear regression, we found a strong predictive relationship between measurements of CP, PT, or PA and the TL of Silver Carp. The CP L ( r 2 = 0.94) and CP W ( r 2 = 0.94) had the strongest relationships with Silver Carp TL, followed by PA1 ( r 2 = 0.89) and PT1 L ( r 2 = 0.87). These strong relationships suggest that all three structures could be used in diet analyses to accurately estimate Silver Carp TL and thus further our understanding of predator–prey dynamics for this high‐risk invasive species.

Illinois↗