Micah G. Bennett

Climate change, hydrology, and fish morphology: predictions using phenotype-environment associations

Phenotype-environment associations (PEAs) describe relationships between the mean phenotypes of a set of populations and the environmental values of the areas in which they inhabit. We show how these PEAs can be used to determine the ability of populations to adapt to future environmental changes, using relationships between fish body shape and stream flow rates as an example. First, we establish that fish in high-flow habitats have more streamlined body shapes than those in low-flow habitats. Then, using future estimates of flow rates obtained from landscape hydrologic models, we predict body shapes of stream fish in the year 2055. Lastly, we use simulations based on a quantitative population genetics model to determine each fish population’s ability to alter its phenotype to the predicted body shape in 2055. While some fish populations were predicted to be able to reach the predicted body shape, others were identified as vulnerable to changing flow rates and may need human assistance to persist into the mid-century. The simulations introduced here combine correlative and mechanistic methods to predict future adaptation to environmental change and are applicable to a wide range of taxa.

Life-History Attributes of the Imperiled Frecklebelly Madtom, Noturus munitus (Siluriformes: Ictaluridae), in the Cahaba River System, Alabama

Abstract Noturus munitus (Frecklebelly Madtom) is a diminutive catfish with a disjunct distribution across the southeastern United States in large rivers and tributaries of the Mobile Basin and Pearl River drainage. Its distribution has contracted since extensive river modification began throughout its range in the 1960s, and it is likely extirpated from the Alabama River. We collected 242 specimens of N. munitus from a gravel island in the Cahaba River on the Coastal Plain in Alabama from May 2005 to March 2007 to examine life-history characteristics. Adults were associated with fast flow over large gravel at depths of 0.5–1.0 m. Young (<23 mm) were found at water depths of 0.4–0.5 m. Gonad development indicated a reproductive season from May to August, with collection of young-of-the-year in June and July supporting a mid- to late-summer spawn. Stomach content analysis revealed a diet similar to other Noturus species and dominated in volume by Baetidae nymphs (31.2%), Hydropsychidae larvae (20.3%), and Simuliidae larvae (19.7%). Some seasonal and sex differences in diet were apparent. Relative fecundity data indicate that N. munitus is one of the most fecund madtoms of the subgenus Rabida (mean of 30.6 mature oocytes) studied thus far. Few males were found in riffles during summer, and no young were found in riffles outside summer, indicating potential sex and size differences in seasonal habitat use. This knowledge is important for conservation of the species.

Status of the Imperiled Frecklebelly Madtom, Noturus munitus (Siluriformes: Ictaluridae): A Review of Data from Field Surveys, Museum Records, and the Literature

Abstract Noturus munitus (Frecklebelly Madtom), is a diminutive catfish restricted to large rivers in the Mobile Basin and Pearl River drainages in the southeastern United States. We conducted surveys of 13 major tributaries of the Alabama, Cahaba, and Tombigbee river systems in the Mobile Basin to determine use of tributaries by N. munitus. Our surveys found only one specimen in Oakmulgee Creek, a large tributary to the Cahaba River and one of the few rivers in which stable populations of N. munitus remain. We combine results from our recent survey with a review of the literature and museum records for N. munitus throughout its range to present a consolidated status report. Our review indicates that N. munitus is currently greatly reduced from its former range, and is in decline in most of the drainages it still inhabits. We recommend federal protection for the species under the Endangered Species Act. We also provide suggestions for future research and management actions for the species.

Timely delivery of scientific knowledge for environmental management: a Freshwater Science initiative

National Center for Environmental Assessment, Office of Research and Development, US Environmental Protection Agency, Washington, DC 20460 USA Department of Infrastructure Engineering, University of Melbourne, Parkville, Victoria 3010, Australia Centre for Evidence Informed Policy and Practice, Australia (https://ceipp.org.au/) Institute for Applied Ecology, University of Canberra, Bruce, Australian Capital Territory, 2617 Australia Centre for Environmental Policy, Imperial College, London, SW7 1NA UK

Response of chlorophyll a to total nitrogen and total phosphorus concentrations in lotic ecosystems: a systematic review protocol

BackgroundEutrophication of freshwater ecosystems resulting from nitrogen and phosphorus pollution is a major stressor across the globe. Despite recognition by scientists and stakeholders of the problems of nutrient pollution, rigorous synthesis of scientific evidence is still needed to inform nutrient-related management decisions, especially in streams and rivers. Nutrient stressor-response relationships are complicated by multiple interacting environmental factors, complex and indirect causal pathways involving diverse biotic assemblages and food web compartments, legacy (historic) nutrient sources such as agricultural sediments, and the naturally high spatiotemporal variability of lotic ecosystems. Determining nutrient levels at which ecosystems are affected is a critical first step for identifying, managing, and restoring aquatic resources impaired by eutrophication and maintaining currently unimpaired resources. The systematic review outlined in this protocol will compile and synthesize literature on the response of chlorophyll a to nutrients in streams, providing a state-of-the-science body of evidence to assess nutrient impacts to one of the most widely-used measures of eutrophication. This review will address two questions: “What is the response of chlorophyll a to total nitrogen and total phosphorus concentrations in lotic ecosystems?” and “How are these relationships affected by other factors?”MethodsSearches for published and unpublished articles (peer-reviewed and non-peer-reviewed) will be conducted using bibliographic databases and search engines. Searches will be supplemented with bibliography searches and requests for material from the scientific and management community. Articles will be screened for relevance at the title/abstract and full text levels using pre-determined inclusion criteria; 10% (minimum 50, maximum 200) of screened papers will be examined by multiple reviewers to ensure consistent application of criteria. Study risk of bias will be evaluated using a questionnaire developed from existing frameworks and tailored to the specific study types this review will encounter. Results will be synthesized using meta-analysis of correlation coefficients, as well as narrative and tabular summaries, and will focus on the shape, direction, strength, and variability of available nutrient-chlorophyll relationships. Sensitivity analysis and meta-regression will be used to evaluate potential effects of study quality and modifying factors on nutrient-chlorophyll relationships.

Mitochondrial DNA divergence in the critically imperilled pygmy madtom, Noturus stanauli (Siluriformes: Ictaluridae)

The mitochondrial cytochrome b gene was sequenced for six individuals of the pygmy madtom, Noturus stanauli, a globally imperilled catfish, from both known localities in Tennessee (U.S.A.) separated by over 1055 river km. Phylogenetic and population genetic analyses revealed little divergence between these populations for this locus.

Performance of National Maps of Watershed Integrity at Watershed Scales

Watershed integrity, the capacity of a watershed to support and maintain ecological processes essential to the sustainability of services provided to society, can be influenced by a range of landscape and in-stream factors. Ecological response data from four intensively monitored case study watersheds exhibiting a range of environmental conditions and landscape characteristics across the United States were used to evaluate the performance of a national level Index of Watershed Integrity (IWI) at regional and local watershed scales. Using Pearson’s correlation coefficient (r), and Spearman’s rank correlation coefficient (rs), response variables displayed highly significant relationships and were significantly correlated with IWI and ICI (Index of Catchment Integrity) values at all watersheds. Nitrogen concentration and flux-related watershed response metrics exhibited significantly strong negative correlations across case study watersheds, with absolute correlations (|r|) ranging from 0.48 to 0.97 for IWI values, and 0.31 to 0.96 for ICI values. Nitrogen-stable isotope ratios measured in chironomids and periphyton from streams and benthic organic matter from lake sediments also demonstrated strong negative correlations with IWI values, with |r| ranging from 0.47 to 0.92, and 0.35 to 0.89 for correlations with ICI values. This evaluation of the performance of national watershed and catchment integrity metrics and their strong relationship with site level responses provides weight-of-evidence support for their use in state, local and regionally focused applications.

Differing Modes of Biotic Connectivity within Freshwater Ecosystem Mosaics

Abstract We describe a collection of aquatic and wetland habitats in an inland landscape, and their occurrence within a terrestrial matrix, as a “freshwater ecosystem mosaic” (FEM). Aquatic and wetland habitats in any FEM can vary widely, from permanently ponded lakes, to ephemerally ponded wetlands, to groundwater‐fed springs, to flowing rivers and streams. The terrestrial matrix can also vary, including in its influence on flows of energy, materials, and organisms among ecosystems. Biota occurring in a specific region are adapted to the unique opportunities and challenges presented by spatial and temporal patterns of habitat types inherent to each FEM. To persist in any given landscape, most species move to recolonize habitats and maintain mixtures of genetic materials. Species also connect habitats through time if they possess needed morphological, physiological, or behavioral traits to persist in a habitat through periods of unfavorable environmental conditions. By examining key spatial and temporal patterns underlying FEMs, and species‐specific adaptations to these patterns, a better understanding of the structural and functional connectivity of a landscape can be obtained. Fully including aquatic, wetland, and terrestrial habitats in FEMs facilitates adoption of the next generation of individual‐based models that integrate the principles of population, community, and ecosystem ecology.

Fish Community Structure and Diet Responses to Newbury Weirs in a Low-Gradient River

Restoration projects are often implemented to address specific issues in the environment. Consequences of a restoration project, if any are measured, typically focus on direct changes to the projects focus. However, changing habitat structure likely results in changes to the environment that affect the communities living there. Rock weirs have been used for channel stabilization in many midwestern rivers. Previous research in a southern Illinois river found that weirs benefitted aquatic macroinvertebrate and riparian bird communities by enhancing habitat heterogeneity and insect emergence production. We hypothesized that fishes would also benefit from weirs through enhanced habitat and food availability. We collected fishes in the Cache River in southern Illinois using hand nets, seines, and electroshocking at sites where weirs had been installed and at non-weir sites. Gut contents were identified and individual food items measured. Fish species richness, but not diversity, was higher at weir sites. Fish communities also differed between site types, with benthic feeders characterizing weir sites. Gut content biomass and abundance differed among fish guilds but not between weir and non-weir sites. Fishes from both site types selected for prey taxa predominately found at weirs. Differences between site types were not always captured by univariate metrics, but connecting fish prey to habitat suggests a reach-scale benefit for fishes through increased abundance of favored prey and enhanced prey diversity. Additionally, given the paucity of rocky substrata in the river as a whole, rock weirs enhance fish species richness by providing habitat for less common benthic species.

Life History Aspects of the Black Madtom,Noturus funebris(Siluriformes: Ictaluridae), in the Cahaba River Drainage, Central Alabama, USA

ABSTRACT The black madtom (Noturus funebris) is a diminutive catfish (maximum standard length 124 mm) found throughout the southeastern United States. Life history aspects of N. funebris were examined using 298 specimens from Blue Girth Creek, a sand-bottomed second-order tributary to the Cahaba River in Bibb County, Alabama, collected in 1987–1988. Noturus funebris was associated with undercut banks, root masses, and woody debris. The youngest reproductive female was 3 years old. Noturus funebris produces many eggs (mean = 109 ova per female) compared to other species within the subgenus Schilbeodes; however, relative fecundity (oocytes per g body weight) indicated a lower relative position in the subgenus. Analysis of gonads and presence of young-of-the-year indicated a spawning season from late June to August. One nest of N. funebris was collected in July 1988 in a glass bottle with 70 eggs. Sex ratio was nearly 1:1. In summer 2005, placement of 30 clay flowerpots as in-stream artificial nesting cavities yielded no additional nests, which suggested a preference for smaller, closed cavities. Analysis of stomach contents indicated a similar diet to other Noturus species, which consisted mainly of decapods and larvae of dipterans, mayflies, and caddisflies. Odonates made up the higher percent of diet volume in winter, crayfish in the spring, and plant material in the summer. Length-frequency data indicated four size (age) classes, with most individuals in the age 0+ and other classes containing similar proportions of individuals. A potential age-4 class consisted of three individuals greater than 108 mm SL.