Occupancy and status of the strawberry darter in the Strawberry River drainage of Arkansas, USA
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Occupancy and status of the strawberry darter in the Strawberry River drainage of Arkansas, USA Kyler B. Hecke & Steve E. Lochmann
Received: 30 May 2020 / Accepted: 18 October 2020 / Published online: 29 October 2020 # Springer Nature B.V. 2020
Abstract 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 K. B. Hecke : S. E. Lochmann Department of Aquaculture and Fisheries, University of Arkansas at Pine Bluff, 1200 North University Drive, Mail Slot 4192, Pine Bluff, AR 71601, USA
Present Address: K. B. Hecke (*) Department of Forestry, Wildlife and Fisheries, University of Tennessee, 2431 Joe Johnson Drive, Knoxville, TN 37996, USA e-mail: [email protected]
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. Keywords Conservation . Freshwater . Modeling . Rivers . Fisheries
Introduction Strawberry Darter Etheostoma fragi (Distler, 1968) is an endemic riffle species in the Strawberry River in Arkansas, USA (Robison et al. 2008) . The Strawberry Darter was first described by Distler (1968) as a sub species of the Orangethroat Darter E. spectabile. Ceas and Page (1997) did thorough sampling and a species description of the Strawberry Darter and suggested it be elevated to the species level. Robison (1998) completed the first distribution survey of the species, where he suggested abundance of E. fragi was declining at many localities, but still appeared to be locally abundant throughout its historical range. However, the Robison (1998) status report was based on abundance data with no statistical
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