Occupancy and Status of the Strawberry Darter in the Strawberry River Drainage of Arkansas, USA

The Strawberry Darter Etheostoma fragi is endemic to the Strawberry River drainage in northcentral Arkansas, where its distribution and status have not been assessed since the mid-1990s. A status survey was conducted during the summers of 2015 and 2016. Sixty-four sites were sampled (32 each summer) within the Strawberry River drainage. Sites were surveyed 4 times each using a kick-seine. A total of 236 E. fragi were observed during the study. E. fragi were observed at 24 of 64 sites, including 15 tributary and 9 main stem sites. Strawberry Darters were observed at sites with a median (range) dissolved oxygen of 9.2 (5.7–11.9) mg/L, median stream flow of 0.2 (0.1–0.7) m/s, median pH of 8.1 (6.7–9.4), median water temperature of 22.0 (13.9–29.3) °C, and median depth of 0.2 (0.1–0.7) m. Presence/absence data were analyzed with occupancy modeling, which estimates informed occupancy rate (hereafter, occupancy) and probability of detection. The drainage-wide occupancy (± SE) was 0.41 ± 0.06 and the probability of detection was 0.56 ± 0.06. A reach covariate model fit our data the best (209.81 AICc). This model estimated an occupancy of 0.54 ± 0.09 and a probability of detection of 0.64 ± 0.06 in the upper reach, an occupancy of 0.20 ± 0.11 and a probability of detection of 0.51 ± 0.17 in the middle reach, and an occupancy of 0.39 ± 0.31 and a probability of detection of 0.19 ± 0.16 in the lower reach The drainage-wide occupancy was lower (0.32 difference) than an occupancy based on historical data (0.73 ± 0.11). These results suggest a decline in the status of E. fragi and justify conservation measures to preserve this species

Movement and Home Range of the Sickle Darter (Percina williamsi) in the Upper Emory River of Tennessee, USA

Understanding movement patterns and home range of rare species is challenging, especially aquatic fauna like fishes. The Sickle Darter Percina williamsi is a rare fish species endemic to the upper Tennessee River basin in eastern Tennessee, southwestern Virginia, and western North Carolina (USA). It has been listed as threatened by the states of Tennessee and Virginia and is being petitioned for federal listing under the United States Endangered Species Act. Little is known about the movement and home range of this species. A total of 8 Sickle Darters from the upper Emory River system were implanted with 8-mm PIT tags and released at the point of capture. The mean (± SD) total length and weight of all fish PIT tagged was 70.1 ± 3.4 mm and 3.08 ± 1.4 g. Movement of individuals was tracked every 2 weeks for 6 months (September–March) with a Biomark® HPR Plus reader and BP Plus portable antenna. Associated environmental data were collected throughout the study. Mean total effort for all the tracking events was 70 ± 39.4 min, mean catch-per-effort was 9.3 ± 6.6 (min/detection) and mean (± SE) detection was 69.5 ± 12%. Mean (± SD) distanced moved of all individuals throughout the study was 7.1 ± 4.5 m. Best sub-sets regressions modelling suggest that Sickle Darter movement is related to discharge (m/s3) at multiple temporal levels (1, 3, or 7-day). Home range for individuals varied in size. Median home range size was 157.5 (86.0–312.5) m2 and median (range) degree of overlap for estimated home range was 23.3 (6.2–34.0) %. The results from this study suggest that Sickle Darters exhibit strong site fidelity except when discharge is extremely high. Therefore, conservation measures that protect or attempt to reconnect fragmented habitats will need to factor in the low dispersal ability of this species

Spatiotemporal Assessment of Sickle Darter (Percina williamsi Page and Near, 2007) Distribution in the Upper Tennessee River Basin

The Sickle Darter Percina williamsi (Page and Near, 2007) is a species of fish endemic to the upper Tennessee River basin in eastern Tennessee, southwestern Virginia, and western North Carolina. Because of its narrow range and presumed decline in occupied sites over the last half century, it is being proposed for federal listing under the Endangered Species Act. We analyzed the current distribution of the Sickle Darter and temporal trends in its distribution in relation to temporal trends in environmental and habitat covariates for each of the historically occupied sub-basins (upper Clinch, Emory, upper French Broad, Little, Little Pigeon, Middle Fork Holston, North Fork Holston, Powell, South Fork Holston, and Watauga) with multiple linear regression modelling. A total of 154 Sickle Darters were observed at 15 sites throughout the upper Tennessee River Basin. Sickle Darters were observed in the Little River, Emory River, and Middle Fork Holston River sub-basins. A total of 133 unique historical occurrences were used for the spatiotemporal analyses. Sickle Darters have declined in 8 out of 10 historically occupied sub-basins. Our best model for the whole distribution scale (Mallow\u27s Cp = −0.87; Adjusted R2 =.92) suggests that habitat fragmentation due to damming has had adverse effects on Sickle Darter populations across its distribution. Models were very similar for the sub-basin specific models as well. The results from this study highlight the drivers of decline in Sickle Darter distribution and outline the future research needs for this species that should be used to inform future conservation decisions regarding this species

Length, Body Depth, and Gape Relationships and Inference on Piscivory among Common North American Centrarchids

Species of Centrarchidae are major components of inland fisheries in much of North America. Thus, information gained from the assessment of interspecies interactions and/or quantifying predator-prey relationships is a useful tool for fisheries managers. Using preserved fish specimens (n = 717) from 20 species of centrarchids, we made measurements of total length (TL), standard length (SL), horizontal gape, and body depth for each individual. We fitted mathematical models that included horizontal gape and body depth as functions of TL and SL, and TL as a function of SL. Linear-regression-model fits were generally good (r2 = 0.764-0.998) for all 20 species, with 61 of 78 possible models having r2 values exceeding 0.90. Horizontal gape-SL (F3,702 = 77.18, P less than 0.001) and body depth-SL (F3,702 = 91.79, P less than 0.001) ratios differed significantly along a gradient that reflected the species\u27 likelihood of piscivory. Slopes of TL-SL regressions did not vary by species, which enabled development of a generalized TL-SL model for centrarchids. Supplemental analyses supported that morphometric measurements had not been influenced significantly by preservation. Results of this study are useful to fisheries managers involved with understanding species interactions within centrarchid-dominated food webs, which are of high priority in most fisheries-management plans

Statistical Parameters

Excel workbook with ANOVA/ANCOVA tables generated by analysis script

Preserved and Live Bluegill

Measurements from preserved and live Bluegill. Each row represents a fish. See readme for column descriptions

Data from: Length, body depth, and gape relationships and inference on piscivory among North American centrarchids

Species of Centrarchidae are major components of inland fisheries in much of North America. Thus, information gained from the assessment of interspecies interactions and/or quantifying predator-prey relationships is a useful tool for fisheries managers. Using preserved fish specimens (n = 717) from 20 species of centrarchids, we made measurements of total length (TL), standard length (SL), horizontal gape, and body depth for each individual. We fitted mathematical models that included horizontal gape and body depth as functions of TL and SL, and TL as a function of SL. Linear-regression-model fits were generally good (r2 = 0.764-0.998) for all 20 species, with 61 of 78 possible models having r2 values exceeding 0.90. Horizontal gape–SL (F3,702 = 77.18, P < 0.001) and body depth-SL (F3,702 = 91.79, P < 0.001) ratios differed significantly along a gradient that reflected the species' likelihood of piscivory. Slopes of TL–SL regressions did not vary by species, which enabled development of a generalized TL–SL model for centrarchids. Supplemental analyses supported that morphometric measurements had not been influenced significantly by preservation. Results of this study are useful to fisheries managers involved with understanding species interactions within centrarchid-dominated food webs, which are of high priority in most fisheries-management plans

Measurement Data

Created using Excel. See Readme for column definitions. Each row corresponds to one specimen