Occupancy and status of the strawberry darter in the Strawberry River drainage of Arkansas, USA

• Published in: Environmental biology of fishes 2020-12, Vol.103 (12), p.1481-1493
• Main Authors: Hecke, Kyler B., Lochmann, Steve E.
• Format: Article
• Language: English
• Subjects: Animal Systematics/Taxonomy/Biogeography; Biomedical and Life Sciences; Detection; Dissolved oxygen; Drainage; Environment; Etheostoma fragi; Freshwater & Marine Ecology; Fruits; History; Life Sciences; Nature Conservation; Occupancy; Probability theory; Rivers; Strawberries; Stream discharge; Stream flow; Summer; Surveying; Water temperature; Wildlife conservation; Zoology
• ISSN: 0378-1909; 1573-5133
• DOI: 10.1007/s10641-020-01037-9

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 AIC c ). 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.