Geology topics

Benjamin H. Stahlschmidt

Publications and source records attributed to Benjamin H. Stahlschmidt.

10 recordsLinked to original sources

USGS2026

Controlling invasive carp ichthyoplankton dispersion using a streamwise-oriented bubble screen: A proof-of-concept validation in a laboratory flume

Recent evidence of invasive grass carp ( Ctenopharyngodon idella ) reproducing in tributaries to the Laurentian Great Lakes has highlighted the need for control efforts targeting multiple life stages. Initial attempts to control dispersal of downstream-drifting invasive carp ichthyoplankton (i.e., eggs and larvae) using an oblique bubble screen (OBS) revealed that nearly neutrally buoyant grass carp eggs and larvae enter helical-like motions driven by the OBS, preventing aggregation within a single capture location. To improve dispersal control methods for such early-life stage carp, we used a laboratory flume to investigate the efficacy of a streamwise-oriented bubble screen to facilitate their near-bank capture. Five early-life stages of grass carp were tested: live water-hardened eggs, pre- and post-gas bladder inflation larvae, dead larvae, and dead eggs (preserved in formalin solution and later rehydrated). A range of mean channel velocities (0.23, 0.45, and 0.75 m/s) was tested for all drifters. Capture percentages increased with increasing airflow. Preserved eggs, for instance, showed capture percentages up to 95 %, 87 %, and 69 % at low, medium, and high water velocities for the highest airflow rate, respectively, in contrast with the lower than 5 % capture measured for zero airflow cases. Symmetric secondary flow structures on either side of the bubble screen induced helical trajectories of drifters and facilitated their capture in net-arrays along each wall. Velocity data were used to estimate helical recirculation timescales, enabling calculation of optimal bubble diffuser and net-array lengths for desired capture rates. This study provides useful guidance for the design of effective systems to control dispersal of downstream-drifting ichthyoplankton of invasive carp in streams.

Journal of Great Lakes Research↗

USGS2026

Development and assessment of fluorescent-dyed, preserved invasive grass carp (Ctenopharyngodon idella) eggs as surrogates for live eggs in transport and dispersal control experiments

Invasive species such as grass carp ( Ctenopharyngodon idella ) pose substantial ecological threats to North American freshwater ecosystems. Understanding their early life stage behavior is critical for management efforts. From spawning to hatching, invasive carp eggs must remain suspended in the water column while drifting downstream for the best chance of survival. This highly vulnerable life stage is a potential target for population control to reduce recruitment. However, studying egg transport and potential dispersal control techniques is challenging, because the availability of live eggs and time period for experimentation are extremely limited. Additionally, accurately replicating the physical characteristics and transport mechanisms of fish eggs using surrogates in laboratory and field studies is not trivial. This study presents a novel method to create fluorescein-dyed, preserved grass carp eggs as surrogates for live eggs in transport and dispersal control experiments. This technique enables year-round studies of grass carp egg transport, offering managers a reliable tool for developing and testing dispersal control and passive sampling methods for invasive carp eggs. In this study, we rehydrate and dye preserved grass carp eggs in varying concentrations of aqueous fluorescein for a range of rehydration times, evaluate dye retention and egg visibility under ultraviolet light (UV-A), and measure diameters and settling velocities for comparison with live eggs. Eggs rehydrated in 0.100 g per liter fluorescein for 30 min maintain adequate brightness for up to 40 min in mixed conditions and exhibit mean settling velocities and densities similar to live eggs, making them ideal for laboratory experiments using quantitative imaging techniques.

River Research and Applications↗

USGS2025

Efficacy of oblique bubble screen deterrents on redirecting live eggs and larvae of grass carp (Ctenopharyngodon idella) at different developmental stages

Invasive carp have severely damaged aquatic ecosystems in the USA, particularly in the Mississippi River Basin. Behavioral deterrents have been developed in the last few decades to control population expansion into new ecosystems. However, none of these deterrents are capable of controlling early-life stage carp, which have limited or no mobility during their drifting stage in rivers. Capturing eggs and larvae in large numbers warrants new methods due to their distinct physical and biological properties as well as their lack of behavioral response. We tested a novel method to redirect downstream drifting eggs and larvae for their efficient removal in streams using an oblique bubble screen (OBS) deterrent. We investigated the effects of mean water velocity and airflow rate on redirection of eggs, pre-gas bladder inflation (GBI) larvae, near-GBI larvae, and dead larvae. Although similar OBS configurations had shown high efficacy redirecting plastic spheres (egg surrogates) in previous studies, they underperform redirecting live eggs and larvae. However, distinct patterns were identified for eggs, pre-GBI, near-GBI, and dead larvae. A detailed hydrodynamic analysis showed that eggs closely follow the larger scales of motions created by the OBS, and that larvae can actively respond to turbulence cues. This study yielded new insights into the movement of early-life stage grass carp in a turbulent flow with strong recirculation, and provided important data to improve the design of bubble screen dispersal barriers for invasive carp management and population control.

Water Resources Research↗

USGS2025

Exploration of a piscicide delivery method for invasive Black Carp

A piscicide delivery method was designed to selectively target Black Carp Mylopharyngodon piceus, an invasive fish species in North America, which possesses pharyngeal teeth adapted for crushing mollusk prey. Many North American mollusks exist in small, fragmented populations susceptible to local extirpation. A Black Carp-selective toxic bait deployed properly could be used to protect those populations. Results represent initial efforts to construct an effective single-dose species-selective toxic bait. We prepared a bait by attaching a glass vial containing toxicant (antimycin A) to the exterior of a Corbicula fluminea clam valve. We designed the vial to break from the force of the fish’s pharyngeal teeth when attempting to crush and consume the clam. We tested suitable vial sizes for encapsulating piscicide and two attachment materials, an aquarium epoxy and ultraviolet light-cured attachment material. The aquarium epoxy was rigid and reinforced vials. The ultraviolet light-cured attachment material was softer, resulting in more vials broken at 3- and 24-h post feeding. In a second trial, toxic baits consisting of antimycin A piscicide were administered in pure ethanol and acetone carriers to Black Carp in assembled baits with vials attached to live clam valves at three concentrations (40.0 mg/mL in ethanol, 170.8 mg/mL and 341.5 mg/mL in acetone). We selected aquarium epoxy for assembled baits based on the bond between the epoxy and glass vial, which allowed a greater surface area to be exposed and broken. While Black Carp successfully broke vials containing piscicide, no treatment caused carp mortality. The delivery method was unsuccessful as a single dose antimycin A piscicide bait for Black Carp. Additional considerations for this approach are provided.

Journal of Fish and Wildlife Management↗

USGS2024

Black carp Mylopharyngodon piceus (Richardson, 1846) mouth gape and size preference of a bivalve prey

Black carp Mylopharyngodon piceus (Richardson, 1846) have been widely used as biological control of snails in aquaculture and were imported to the United States in the 1970s and 1980s for this purpose. Prior research emphasizes the species’ propensity to control gastropods, but since subsequent escape and establishment of black carp in portions of the Mississippi River Basin, concerns now focus on the numerous endangered and endemic bivalve species upon which black carp may predate. Black carp mouth gape may limit predation on larger bivalves, but bite force is also a factor. We used regression of fish length to mouth gape of wild-caught black carp and compared these results to tank forage size preference trials with bivalve prey Corbicula fluminea clams. Wild-caught black carp ranged from 429 to 1580 mm total length, a size range larger than measured in previous studies. Regression of fish length and mouth gape indicated greater variability among sizes, as expected from wild versus cultured populations. Clam consumption was size-dependent. Black carp commonly engulfed but did not consume the largest clams in tank feeding trials. Shell width was a better predictor of successful consumption than length or height. Predation was restricted at sizes less than the mouth gape of test black carp as observed by individuals engulfing but failing to consume prey. This result indicates that either bite force or the pharyngeal apparatus gape (i.e., the distance between the pharyngeal teeth and keratinous pad) limited successful crushing of engulfed shells. Bivalve predation by black carp is limited by both a fish’s ability to engulf prey and the ability to fracture the shell of larger prey items that cannot be broken or swallowed whole. The results of this research may be used to assess potential prey sizes of wild black carp and anticipated effects of predation on bivalve communities.

Journal of Applied Ichthyology↗

USGS2021

Using turbulence to identify preferential areas for grass carp (Ctenopharyngodon idella) larvae in streams: A laboratory study

In this experimental series, we studied the swimming capabilities and response of grass carp ( Ctenopharyngodon idella ) larvae to flow turbulence in a laboratory flume. We compared three different experimental configurations, representing in‐stream obstructions commonly found in natural streams (e.g., a gravel bump, a single vertical cylinder, and patches of submerged rigid vegetation). Grass carp larvae (postgas bladder emergence) were introduced to each experimental configuration and subjected to a variety of hydrodynamic forces of different magnitudes and scales. We varied the flow velocities and water depths and found ranges of turbulent kinetic energy and Reynolds stresses that triggered a response in larval trajectories, identified by measured horizontal and vertical swimming speeds for each flow condition. Larvae apparently actively avoided areas with increased levels of turbulence by swimming away, moving faster in short bursts, and expending more energy. In addition to the magnitude of turbulent kinetic energy, the length scale and time scale of turbulent eddies also influenced the larvae response. These findings support the development of new strategies for controlling the spread of grass carp larvae in rivers, as well as the development of numerical tools incorporating active swimming capabilities to predict larval transport in streams.

Water Resources Research↗

USGS2020

Identifying turbulence features hindering swimming capabilities of grass carp larvae (Ctenopharyngodon idella) through submerged vegetation

Aquatic vegetation can provide habitat and refuge for a variety of species in streams. However, the flow features generated by submerged patches of vegetation can also pose a challenge for fish larvae. We conducted a series of experiments with live grass carp larvae (starting ∼50 h post hatch) in a laboratory racetrack flume, using a submerged array of rigid cylinders to mimic vegetation. We used particle image velocimetry to characterize the flow field, and particle tracking velocimetry to obtain position and displacement of the fish. Four speeds and two submergence ratios were investigated. In contrast with previous studies with grass carp eggs, our data showed an active response from larvae to determine their position. Our study shows that: (1) mean velocity by itself is not a reliable predictor, as some larvae will seemingly prefer to be in areas of higher speeds with lower shear and turbulence, (2) turbulence characteristics can be used to identify areas avoided by larvae, (3) turbulence length scales are relevant to determine spatial distribution of larvae and their swimming capabilities within and above vegetated patches and similar roughness elements in streams. These findings can inform the design of monitoring and control strategies in rivers based on turbulence and turbulence scales generated by natural and man-made instream structures.

Journal of Ecohydraulics↗

USGS2019

Influence of turbulence and in-stream structures on the transport and survival of grass carp eggs and larvae at various developmental stages

Understanding the response of grass carp to flow and turbulence regimes during early life stages is fundamental to monitoring and controlling their spread. A comprehensive set of hydrodynamic experiments was conducted with live grass carp eggs and larvae, to better understand their drifting and swimming patterns with 3 different in-stream obstructions: (1) a gravel bump, (2) a single cylinder, and (3) submerged vegetation. The hydrodynamic behavior of eggs and larvae with each obstruction was continuously monitored for about 85 consecutive hours. Transient spatial distributions of the locations of eggs and larvae throughout the water column were generated for each flow scenario. Results show that the active swimming capabilities of larvae allow them to seek areas of low turbulence and low shear stresses, and that eggs are susceptible to damage by high levels of turbulence, which was further corroborated with tests in an oscillating grid-stirred turbulence tank. Our study seeks to better inform field collection of grass carp during early life stages, and to guide the design of alternative approaches to control the dispersal of this invasive species in North America.

Aquatic Sciences↗

USGS2018

Survival and drifting patterns of grass carp eggs and larvae in response to interactions with flow and sediment in a laboratory flume

A series of laboratory experiments was conducted to better understand the behavior of grass carp eggs and larvae in moving water in order to develop and implement new strategies for control and prediction of their dispersal and drift at early life stages. Settling velocity and density of a representative sample of eggs were estimated, and three trials of flume experiments with different flow conditions were conducted with live eggs in a temperature-controlled setting with a mobile sediment bed. In these trials, egg and larval stages were continuously analyzed over periods of 80 hours; and eggs and larvae interactions with the flow and sediment bed were monitored and characterized qualitatively and quantitatively. Survival rates were quantified after each trial, highlighting physical causes for increased mortality. Detailed flow analysis was correlated to the observed drifting and swimming behavior of eggs and larvae, to estimate distributions across the water depth, as well as traveling and swimming speeds. Evidence of the influence of mean and turbulent flow in the suspension and transport of eggs are reported, and swimming patterns of larvae at different developmental stages are described. These findings support the development of new strategies for monitoring the spread of grass carp eggs and larvae in rivers, and provide new inputs to predict conditions favorable for spawning and hatching, allowing for mitigation measures at early life stages, which are critical to control their dispersal.

PLoS ONE↗

USGS2018

Ontogenetic changes in swimming speed of silver carp, bighead carp, and grass carp larvae: implications for larval dispersal

Bighead, silver, and grass carps are invasive in the waterways of central North America, and grass carp reproduction in tributaries of the Great Lakes has now been documented. Questions about recruitment potential motivate a need for accurate models of egg and larval dispersal. Quantitative data on swimming behaviors and capabilities during early ontogeny are needed to improve these dispersal models. We measured ontogenetic changes in routine and maximum swimming speeds of bighead, grass, and silver carp larvae. Daily measurements of routine swimming speed were taken for two weeks post-hatch using a still camera and the LARVEL program, a custom image-analysis software. Larval swimming speed was calculated using larval locations in subsequent image frames and time between images. Using an endurance chamber, we determined the maximum swimming speed of larvae (post-gas bladder inflation) for four to eight weeks post-hatch. For all species, larval swimming speeds showed similar trends with respect to ontogeny: increases in maximum speed, and decreases in routine speed. Maximum speeds of bighead and grass carp larvae were similar and generally faster than silver carp larvae. Routine swimming speeds of all larvae were highest before gas bladder inflation, most likely because gas bladder inflation allowed the fish to maintain position without swimming. Downward vertical velocities of pre-gas bladder inflation fish were faster than upward velocities. Among the three species, grass carp larvae had the highest swimming speeds in the pre-gas bladder inflation period, and the lowest speeds in the post-gas bladder inflation period. Knowledge of swimming capability of these species, along with hydraulic characteristics of a river, enables further refinement of models of embryonic and larval drift.

PeerJ↗