SFS Annual Meeting

5/20/2019  |   11:00 - 11:15   |  151 G

THE RIVER CONTINUUM CONCEPT PREDICTS FISH PREY ASSEMBLAGE STRUCTURE FOR AN INSECTIVOROUS FISH ALONG A TEMPERATE RIVERSCAPE The river continuum concept (RCC) provides a framework for processes structuring lotic ecosystems by synthesizing sources and transport of C in streams. The RCC has received considerable attention since its inception >35 y ago, but few investigators have tested its predictions by explicitly linking consumer groups. We assessed insect assemblage structure in the diet of a broadly distributed insectivorous fish (Cottus carolinae) in Tennessee to test 3 predictions from the RCC: 1) longitudinal change in relative biomass of insect functional feeding groups (FFGs); 2) maximum taxonomic diversity at stream orders 3 to 5; and 3) temporal turnover in taxonomic composition across 1 y. We found that relative biomass of insect FFGs consumed by C. carolinae broadly matched predictions from the RCC. Maximum taxonomic diversity assessed at the family rank occurred at stream order 4, and monthly prey assemblages followed a sequence of turnover and a return to starting conditions across 1 y. Our approach illustrates proof of concept that RCC tenets are integrated into the diet of at least 1 higher-level consumer and transcend assemblage boundaries in regulating the longitudinal and vertical flow of C in streams.

Joshuah Perkin (Primary Presenter/Author), Texas A&M University , jperkin@tamu.edu;


William Curtis (Co-Presenter/Co-Author), Tennessee Tech University, mrlliw1@gmail.com;


Amy Gebhard (Co-Presenter/Co-Author), South Dakota Game, Fish, and Parks, amy.e.doll1@gmail.com;


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5/20/2019  |   11:15 - 11:30   |  151 G

TROPHIC STRUCTURE OF FISH ASSEMBLAGES ACROSS RIVER CONTINUA: CHALLENGES AND OPPORTUNITIES FOR BIOASSESSMENT In large stream networks, feeding ecology of fish species and the breadth of food resources used by assemblages are influenced by a great deal of variation in physiography, climate, flow conditions and ecosystem size. Because assessments of trophic diversity are often used for evaluating ecological integrity of habitats, an understanding of this variation is essential. The River Continuum Concept and other theories regarding longitudinal shifts in food resource use provide expectations for trophic structure of fish assemblages that may apply across regions, but exceptions to these expectations have revealed important challenges. For example, natural climatic differences within large river basins may influence trophic diversity of fish assemblages in streams with similar network positions and elevations. In many systems, expected shifts in resources are interrupted by flow alteration, which causes discontinuities in spatial patterns of geomorphology, discharge, and food resource availability in ways that may be difficult to predict. Promising areas for future research to reveal patterns of trophic structure of fish assemblages across river continua include investigations in under-studied biomes, examinations of temporal variation, and measurements of the extent of individual specialization across habitats.

Allison Pease (Primary Presenter/Author), Texas Tech University, allison.pease@ttu.edu ;


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5/20/2019  |   11:30 - 11:45   |  151 G

ARE FISH EXPOSED TO PARASITE INFECTION GRADIENTS ALONG THE RIVER CONTINUUM? The river continuum concept (RCC) hypothesizes that longitudinal gradients in physical conditions from headwaters to rivers cause predictable changes in species richness and composition of stream communities. Fish and macroinvertebrate assemblages have been well studied along the continuum, whereas fish parasites have not. We collected and necropsied 421 Redspot Darters (Etheostoma artesiae) from 15 streams ranging from 2rd to 7th order in the Bankhead National Forest of Alabama, and quantified presence-absence of microparasites and abundance of macroparasites. Total parasite richness, richness of parasites with totally aquatic life cycles, those with 2-host life cycles, and microparasite richness increased with stream size (as drainage area, DA), as did mean richness among hosts. Prevalence of parasites (% hosts infected) with 3-host life-cycles, those using darters as their final host, and helminths increased with DA. The mean abundance of parasites with 3-host life cycles also increased with DA. Our results support the predictions of the RCC because E. artesiae populations experienced parasite infection gradients in richness, prevalence, and mean abundance of species and trait (life cycle) groups along the river continuum. Furthermore, these infection gradients appear to have predictable relationships with stream size.

Brian Helms (Co-Presenter/Co-Author), Troy University, helmsb@troy.edu;


Jack Feminella (Co-Presenter/Co-Author), Auburn University, feminjw@auburn.edu;


Eric Bauer (Primary Presenter/Author), Auburn University, efb0005@tigermail.auburn.edu;


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5/20/2019  |   11:45 - 12:00   |  151 G

DECADAL DIFFERENCES IN RIPARIAN LEAF LITTER SUBSIDIES AND DECOMPOSITION AT AUGUSTA CREEK Augusta Creek, a tributary in Southwest Michigan, has hosted field studies that revolutionized stream ecology and changed the way riverine systems were viewed. Descriptive studies on leaf litter decomposition in the 1970’s served as formative evidence for the River Continuum Concept. Yet, these studies were limited by their time. Genomic technologies were not developed for microbial community assessment and riparian invaders were not yet a concern. Several invasions, including Common Buckthorn and Emerald Ash Borer, reshaped riparian conditions and leaf litter inputs of Augusta Creek; therefore, it serves as an ideal site to revisit the hypotheses tested forty years ago, updated to address colonizing microbes and invasion dynamics. The aim was to determine how leaf taxa (invasive vs. native) alters leaf litter decomposition rates as well as the macroinvertebrate and microbial communities. Preliminary analysis determined faster decomposition and different microbial colonizers in the invasive leaf litter. We also compare these findings to those of Petersen and Cummins (1974), who found different processing rates and colonization among leaf taxa. This experiment continues the legacy of leaf litter decomposition research at Augusta Creek, informing larger fields of invasive species and microbial ecology.

Courtney Larson (Primary Presenter/Author), U.S. Environmental Protection Agency, larson.courtney@epa.gov;
U.S. EPA

M. Eric Benbow (Co-Presenter/Co-Author), Michigan State University, benbow@msu.edu;


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