Geology topics

Holly S. Embke

Publications and source records attributed to Holly S. Embke.

5 recordsLinked to original sources

USGS2023

Potential effects of climate change on Acipenser fulvescens (lake sturgeon)

Acipenser fulvescens (Rafinesque, 1817; lake sturgeon) are the only sturgeon species native to the Great Lakes region and are threatened across most of their range. They are historically vulnerable because of overfishing and habitat fragmentation with the potential for climate change acting as an increasing stressor in the future. Lake sturgeon span multiple habitats during their long lifespans, including high gradient streams, nearshore areas, and deep rivers and lakes. Climate change is projected to strongly affect the suitability of these habitats through increasing precipitation and temperatures and decreasing ice cover and snowmelt. Changes in flow timing and amount can affect movement to spawning and nursery sites, and increased water temperatures are likely to affect species activity patterns, survival, and prey availability. Ultimately, the Great Lakes region is expected to face wide ranging effects from climate change, which may have positive and negative effects on lake sturgeon depending on a variety of factors, including the life stages affected, habitat availability, and interactions with other stressors, but all shifts are likely to affect spawning. Importantly, several areas of further research would be beneficial to understanding the complex effects of climate change on lake sturgeon.

Great Lakes↗

USGS2021

Status of the major aquaculture carps of China in the Laurentian Great Lakes Basin

There is concern of economic and environmental damage occuring if any of the four major aquacultured carp species of China, black carp Mylopharyngodon piceus , bighead carp Hypophthalmichthys nobilis , silver carp H. molitrix , or grass carp Ctenopharyngodon idella , were to establish in the Laurentian Great Lakes. All four are reproducing in the Mississippi River Basin. We review the status of these fishes in relation to the Great Lakes and their proximity to pathways into the Great Lakes, based on captures and collections of eggs and larvae. No black carp have been captured in the Great Lakes Basin. One silver carp and one bighead carp were captured within the Chicago Area Waterway System, on the Great Lakes side of electric barriers designed to keep carp from entering the Great Lakes from the greater Mississippi River Basin. Three bighead carp were captured in Lake Erie, none later than the year 2000. By December 2019, at least 650 grass carps had been captured in the Great Lakes Basin, most in western Lake Erie, but none in Lake Superior. Grass carp reproduction has been documented in the Sandusky and Maumee rivers in Ohio, tributaries of Lake Erie. We also discuss environmental DNA (eDNA) results as an early detection and monitoring tool for bighead and silver carps. Detection of eDNA does not necessarily indicate presence of live fish, but bigheaded carp eDNA has been detected on the Great Lakes side of the barriers and in a small proportion of samples from the western basin of Lake Erie.

Illinois, Indiana↗

USGS2019

Variation in Bluegill catch rates and total length distributions among four sampling gears used in two Wisconsin lakes dominated by small Ffsh

Many Bluegill Lepomis macrochirus populations are dominated by fish ≤125 mm total length (TL) that may be underrepresented when using standard sampling gears. To identify efficient sampling methods for these populations, we compared catch per unit effort (CPUE) and TL frequency distributions of Bluegill captured in cloverleaf traps, boat electrofishing, mini-fyke nets, and beach seine hauls from two northern Wisconsin lakes supporting populations dominated by fish ≤125 mm TL. Mean Bluegill CPUE ranged from 41 (SE = 11) fish per cloverleaf trap lift to 16 (SE = 8) fish per beach seine haul. Cloverleaf traps generally captured smaller Bluegill relative to other gears and were the only gear to consistently capture Bluegill ≤80 mm TL. Conversely, boat electrofishing captured the widest TL range of Bluegill, and fish ≥80 mm TL composed a greater proportion of catch (37%) relative to other gears. With few exceptions, the effort required to detect 10% or 25% changes in Bluegill CPUE was >100 units of effort regardless of lake, sampling gear, or month. Furthermore, there was no consistency between lakes or months in terms of which sampling gear required the fewest number of samples to detect a 50% change in CPUE. Estimated units of effort needed to detect 10% or 25% changes in mean Bluegill TL were ≤16 for all sampling gears on the lake with consistently higher CPUE (i.e., more fish to measure per unit). In the lake with lower CPUE, cloverleaf traps consistently required less effort to detect changes in mean TL. We note that comparing sample size requirements among gears is not straightforward because gears are sampling differing segments of the Bluegill population. Our study emphasizes the importance of evaluating gear biases and sampling efficiency so that fisheries managers can develop suitable sampling protocols.

Wisconsin↗

USGS2019

Modeling framework to estimate spawning and hatching locations of pelagically-spawned eggs

Identifying spawning and hatching locations is vital to controlling invasive fish and conserving imperiled fish, which can be difficult for pelagically-spawning species with semi-buoyant eggs. In freshwater systems, this reproductive strategy is common among cyprinid species, such as Chinese carp species currently threatening the Great Lakes. Following the confirmation that one of these species, Grass Carp (Ctenopharyngodon idella), was spawning in a Great Lakes tributary, we developed a modeling framework to combine field data with hydraulic models to calculate the most probable spawning and hatching locations for collected eggs. Our results indicate that the estimated spawning location encompassed habitat consistent with spawning sites in Grass Carp’s native range. Additionally, all eggs were identified to have hatched in the river, increasing the likelihood of successful recruitment. This modeling framework can be used to estimate spawning and hatching locations for Chinese carp species, as well as all pelagic, riverine spawners. Spawning and hatching locations provide key information to researchers about the reproductive requirements of species and to agencies about how best to manage populations for control or restoration.

Canadian Journal of Fisheries and Aquatic Sciences↗

USGS2016

First direct confirmation of grass carp spawning in a Great Lakes tributary

Grass carp ( Ctenopharyngodon idella ), an invasive species of Asian carp, has been stocked for many decades in the United States for vegetation control. Adult individuals have been found in all of the Great Lakes except Lake Superior, but no self-sustaining populations have yet been identified in Great Lakes tributaries. In 2012, a commercial fisherman caught four juvenile diploid grass carp in the Sandusky River, a major tributary to Lake Erie. Otolith microchemistry and the capture location of these fish permitted the conclusion that they were most likely produced in the Sandusky River. Due to this finding, we sampled ichthyoplankton using paired bongo net tows and larval light traps during June–August of 2014 and 2015 to determine if grass carp are spawning in the Sandusky River. From the samples collected in 2015, we identified and staged eight eggs that were morphologically consistent with grass carp. Five eggs were confirmed as grass carp using quantitative Polymerase Chain Reaction for a grass carp-specific marker, while the remaining three were retained for future analysis. Our finding confirms that grass carp are naturally spawning in this Great Lakes tributary. All eggs were collected during high-flow events, either on the day of peak flow or 1–2 days following peak flow, supporting an earlier suggestion that high flow conditions favor grass carp spawning. The next principal goal is to identify the spawning and hatch location(s) for the Sandusky River. Predicting locations and conditions where grass carp spawning is most probable may aid targeted management efforts.

Lake Erie, Sandusky River↗