Multispecies Occupancy Modeling as a Tool for Evaluating the Status and Distribution of Darters in the Elk River, Tennessee

Abstract

Sixteen darter species, including the federally endangered Boulder Darter Etheostoma wapiti, are known to occur in the Elk River, a large, flow‐regulated tributary of the Tennessee River, Tennessee–Alabama. Since the construction of Tims Ford Dam (TFD) in 1970, habitat modification caused by cold, hypolimnetic water releases and peak‐demand hydropower generation has contributed to population declines and range reductions for numerous aquatic species in the main‐stem Elk River. We developed Bayesian hierarchical multispecies occupancy models to determine the influence of site‐ and species‐level characteristics on darter occurrence by using presence–absence data for 15 species collected from 39 study sites. Modeling results indicated that large‐river obligate species, such as the Boulder Darter, were 6.92 times more likely to occur for every 37‐km increase in the distance downstream from TFD. In contrast, small‐stream species were 2.35 times less likely and cosmopolitan species were 1.88 times less likely to occur for every 37‐km increase in distance downstream from TFD. The probability of occurrence for darter species also had a strong negative relationship with the absence of cobble and boulder substrates and the presence of high silt levels, particularly for species that require boulder substrates during spawning. Although total darter species richness was similar across all 39 sample sites, the composition of darter assemblages varied substantially among locations, presumably due in part to species‐specific habitat affinities and hydrothermal conditions. The use of multispecies occupancy models allowed us to account for the incomplete detection of species while estimating the influence of physical habitat characteristics and species traits on darter occurrences, including rarely observed species that would have been difficult to model individually. Received August 23, 2015; accepted May 31, 2016 Published online August 12, 2016

A Thermally Stratified Reservoir Module for Large‐Scale Distributed Stream Temperature Models With Application in the Tennessee River Basin

“…We also obtained river temperature measurements at five locations downstream of Tims Ford Reservoir along the Elk River. These temperature measurements were collected during the summer from 2005 to 2012 as part of a biological study of dam releases (Potoka et al, 2016).…”

Differences in Native and Invasive Fish Larval Occupancy and Detection Probabilities in the Upper Mississippi River

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The context dependency of fish‐habitat associations in separated karst ecoregions

“…For example, many fishes in the Ozark Highlands and Great Plains ecoregions appear to have recolonized northern areas of the range from a southern Ozark Highland refuge (e.g., carmine shiner Notropis percobromus , Berendzen et al., 2008 ). Distribution information on populations is useful for a variety of conservation and management needs including identifying habitat refugia over time (Lake, 2000 ; Magoulick & Kobza, 2003 ; Peterson & Rabeni, 1996 ; Torgersen et al., 1999 ), identifying locations to manage with limited resources (Dauwalter & Rahel, 2008 ; Gardner et al., 2013 ; Gore et al., 2001 ; Park et al., 2003 ; Rabeni & Sowa, 1996 ; Wilson et al., 2005 ), determining species conservation status (e.g., goldline darter Percina aurolineata , Albanese et al., 2004 ; Potoka et al., 2016 ), and identifying areas of reintroduction (Bearlin et al., 2002 ; Wall et al., 2004 ). Reconnecting naturally isolated populations is not a management goal; however, understanding how these populations persist across different landscapes is helpful to developing meaningful conservation and management actions (i.e., are the populations limited by different physicochemical conditions?).…”