Geology topics

James B. Layzer

Publications and source records attributed to James B. Layzer.

7 recordsLinked to original sources

USGS2014

Population demographics and life history of the round hickorynut (Obovaria subrotunda) in the Duck River, Tennessee

Population characteristics and life history aspects of healthy mussel populations are poorly understood. The reproductive cycle, age and growth, and population structure of Obovaria subrotunda were examined at four sites in the middle Duck River, Tennessee. Obovaria subrotunda was confirmed to be a bradytictic species, spawning in the late summer and holding glochidia in the gills for 11 mo until the following summer. Fecundity was positively related to mussel length (R 2 = 0.75) and ranged from 7122 to 76,584 glochidia. Fourteen species of fish found in the Duck River, in the families Percidae, Cyprinidae, and Cottidae, were infested with glochidia in the laboratory to examine potential hosts. Juveniles transformed on Etheostoma blennioides (greenside darter), E. obama (spangled darter), E. flabellare (fantail darter), and Cottus carolinae (banded sculpin). Analyses of shell thin-sections indicated that males grew faster and obtained a larger size than females. Individuals live to at least 14 y old. Females became sexually mature at age one. Four sites were quantitatively sampled using a systematic design with three random starts. The observed ratio of adult males to females (0.9∶1) did not differ significantly from 1∶1. Results of the quantitative sampling showed an increase in density compared to earlier studies and a high proportion of 1 to 5 y old O. subrotunda .

Tennessee↗

USGS2013

Consumption of freshwater bivalves by muskrats in the Green River, Kentucky

Muskrats (Ondatra zibethicus) are known to prey on freshwater bivalves (mussels and clams) and can negatively impact imperiled mussel species. However, factors that influence muskrat predation on bivalves are poorly understood. We evaluated the feeding ecology of muskrats in the Green River, Kentucky, by using stable isotope analysis of muskrat hair samples and by monitoring bivalve shell deposition at muskrat middens. Bayesian mixing-model analysis of stable isotope δ 15 N and δ 13 C ratios revealed that the median muskrat biomass derived from bivalves was 51.4% (5th and 95th percentiles were 39.1 to 63.4%, respectively), a much higher dietary proportion than previously reported. Shell depositions by muskrats at middens decreased with the availability of seasonal emergent vegetation, suggesting that the consumption of animal matter is in response to a scarcity of plant foods, perhaps exacerbated by the altered flow regimes on the Green River. Our results add to the growing body of evidence that muskrats have the potential to impact mussel population growth and recovery in some environments.

Kentucky↗

USGS2011

A comparison of turtle sampling methods in a small lake in Standing Stone State Park, Overton County, Tennessee

We used basking traps and hoop nets to sample turtles in Standing Stone Lake at 2-week intervals from May to November 2006. In alternate weeks, we conducted visual basking surveys. We collected and observed four species of turtles: spiny softshell (Apalone spinifera), northern map turtle (Graptemys geographica), pond slider (Trachernys scripta), and snapping turtle (Chelydra serpentina). Relative abundances varied greatly among sampling methods. To varying degrees, all methods were species selective. Population estimates from mark and recaptures of three species, basking counts, and hoop net catches indicated that pond sliders were the most abundant species, but northern map turtles were 8Ã— more abundant than pond sliders in basking trap catches. We saw relatively few snapping turtles basking even though population estimates indicated they were the second most abundant species. Populations of all species were dominated by adult individuals. Sex ratios of three species differed significantly from 1:1. Visual surveys were the most efficient method for determining the presence of species, but capture methods were necessary to obtain size and sex data.

Tennessee↗

USGS2010

Summer microhabitat use by adult and young-of-year snail darters (Percina tanasi) in two rivers

We characterised microhabitat availability and use by adult and young‐of‐year (YOY) snail darters ( Percina tanasi Etnier 1976 ) while snorkelling in the French Broad and Hiwassee rivers, TN, USA. Both age groups of snail darters disproportionately used most microhabitat variables compared to their availability. Snail darters primarily occupied moderately deep, swift water over gravel substrates with little macrophyte coverage and no silt. Univariate comparisons indicated that adult and YOY darters occupied different habitat, but there was no marked differences between principal components analysis plots of multivariate microhabitat use within a river. Although the availability of microhabitat variables differed between the French Broad and Hiwassee rivers, univariate means and multivariate plots illustrated that the habitats used were generally similar by age groups of snail darters between rivers. Because our observations of habitat availability and use were constrained to low flow periods and depths <1 m, the transferability of our results to higher flow periods may be limited. However, the similarity in habitat use between rivers suggests that our results can be applied to low‐normal flow conditions in other streams.

Ecology of Freshwater Fish↗

USGS2008

Age-class structure and variability of two populations of the bluemask darter etheostoma (Doration) sp.

The bluemask darter Etheostoma ( Doration ) sp. is an endangered fish endemic to the upper Caney Fork system in the Cumberland River drainage in central Tennessee. Darters ( Etheostoma spp.) are typically short-lived and exhibit rapid growth that quickly decreases with age. Consequently, estimating age of darters from length-frequency distributions can be difficult and subjective. We used a nonparametric kernel density estimator to reduce subjectivity in estimating ages of bluemask darters. Data were collected from a total of 2926 bluemask darters from the Collins River throughout three growing seasons. Additionally, data were collected from 842 bluemask darters from the Rocky River during one growing season. Analysis of length-frequencies indicated the presence of four age classes in both rivers. In each river, the majority of the population was comprised of fish <3 y old. Some age-one individuals were sexually mature, but the majority of the reproductive population was comprised of older fish. Differences in age-class structure among years reflected variable year-class strength in the Collins River that seemed related to summer discharge. Male and female growth rates differed significantly (P < 0.05); males were typically larger than females of the same age after the first growing season and the majority of age-three individuals were males. Growth rates in the Collins and Rocky Rivers were similar for each sex (P > 0.05). In both rivers, females were more abundant than males.

Tennessee↗

USGS2006

Mussels: The forgotten fauna of regulated rivers. A case study of the Caney Fork River

During the past century freshwater mussel populations have declined precipitously throughout North America. Much of this loss has resulted from the construction of dams. In the Cumberland River system, 23% (22 species) of the historic mussel fauna is extinct or listed as endangered. Several additional species have either been extirpated from the Cumberland River or exist only in small, non-reproducing populations. Mussels of headwater streams have been severely affected by coal mining and poor land use practices. An intensive survey was conducted in the Caney Fork River, a major tributary to the Cumberland River, to determine the historic and extant mussel fauna. The results indicate that at least 37 species of mussels have been extirpated from the Caney Fork River, mainly as a result of the construction and operation of the Center Hill Dam. Among the species extirpated, two are now extinct, five are endangered and five are candidates for listing as threatened or endangered. Effects associated with this dam include the inundation of 102 km of riverine habitat, the discharge of hypolimnetic water (which limits mussel reproduction) and an alternating pattern of stream bed scouring and dewatering. The recognition of mussel life history requirements during preconstruction could have reduced many of these effects.

North Carolina↗

USGS2001

Macroinvertebrate instream flow studies after 20 years: A role in stream management and restoration

Over the past two decades of refinement and application of instream flow evaluations, we have examined the hydraulic habitat of aquatic macroinvertebrates in a variety of conditions, along with the role of these macroinvertebrates in sustaining ecosystem integrity. Instream flow analyses assume that predictable changes in channel flow characteristics can, in turn, be used to predict the change in the density or distribution of lotic species or, more appropriately, the availability of useable habitat for those species. Five major hydraulic conditions most affect the distribution and ecological success of lotic biota: suspended load, bedload movement, and water column effects, such as turbulence, velocity profile, and substratum interactions (near-bed hydraulics). The interactions of these hydraulic conditions upon the morphology and behavior of the individual organisms govern the distribution of aquatic biota. Historically, management decisions employing the Physical Habitat Simulation (PHABSIM) have focused upon prediction of available habitat for life stages of target fish species. Regulatory agencies have rarely included evaluation of benthos for flow reservations. Although ‘taxonomic discomfort’ may be cited for the reluctant use or creation of benthic criteria, we suggest that a basic misunderstanding of the links between benthic macroinvertebrate and the fish communities is still a problem. This is derived from the lack of a perceived ‘value’ that can be assigned to macroinvertebrate species. With the exception of endangered mussel species (for which PHABSIM analysis is probably inappropriate), this is understandable. However, it appears that there is a greater ability to predict macroinvertebrate distribution (that is, a response to the change in habitat quality or location) and diversity without complex population models. Also, habitat suitability criteria for water quality indicator taxa (Ephemeroptera, Plecoptera, and Trichoptera; the so-called ‘EPTs’) may also provide additional management options to stream regulators. The greatest application for macroinvertebrate criteria will be in low-order streams where a more immediate link to fish communities can be established. We present an example from Queens Creek, in North Carolina, USA, in which monthly allocations required to preserve the integrity of the benthic macroinvertebrate community were significantly higher than for the target benthic fish species, Cottus bairdi . In the months when both Cottus and community diversity of macroinvertebrates were the ‘bottleneck’ life stages, preservation of only fish species could result in an additional 5–25% loss in macroinvertebrate habitat. We suggest that, as there becomes an increased emphasis on maintaining macroinvertebrates as monitors of stream health, there will be a concurrent emphasis on incorporating hydraulic habitat conditions as a part of bioassessment.

Regulated Rivers: Research & Management↗