Characterizing the distribution of the critically endangered estuarine pipefish (Syngnathus watermeyeri) across its range using environmental DNA. Issue 1 (7th October 2022)

• Record Type: Journal Article
• Authors: Nester, Georgia M.; Heydenrych, Matthew J.; Berry, Tina E.; Richards, Zoe; Wasserman, Johan; White, Nicole E.; De Brauwer, Maarten; Bunce, Mike; Takahashi, Miwa; Claassens, Louw
• Is Part Of: Environmental DNA. Volume 5:Issue 1(2023)
• Page Start: 132
• Page End: 145
• Publication Date: 2022-10-07
• Subjects: barcoding -- biomonitoring -- conservation -- cryptobenthic -- endangered species -- Syngnathidae; DNA -- Periodicals; Biology -- Periodicals; Microbial ecology -- Periodicals; Biology; DNA; Microbial ecology; Electronic journals; Periodicals; 572.86
• DOI: 10.1002/edn3.365
• Languages: English
• ISSNs: 2637-4943

Abstract

Abstract: The effective management of rare and threatened species, especially in areas where population sizes have diminished, relies on knowledge of their population size, threats, and distribution. Robust mapping of distribution presents a particular challenge in aquatic environments for cryptic species, especially those with low abundance. Environmental DNA (eDNA) approaches can offer improved detection rates of many rare and threatened species when compared with traditional sampling approaches. In this study, we developed and optimized a targeted eDNA assay for the critically endangered estuarine pipefish ( Syngnathus watermeyeri ). eDNA sampling and seine netting were undertaken at 39 sites across the historical range of S. watermeyeri in the Eastern Cape of South Africa in 2019. At each site, five water samples were collected for eDNA analysis ( n = 195) along with three seine netting hauls ( n = 117). Habitat and environmental data were collected at each location to explore what physical and biotic parameters might correlate with pipefish presence/absence. We successfully detected S. watermeyeri in two estuaries (Kariega and Bushmans) using both survey methods. Importantly, the positive detection rate of eDNA (66.7%) was four times that of seine netting (16.7%), highlighting the value of eDNA as a monitoring tool for rare and cryptic species. Null detections in the Kasouga, East Kleinemonde, and West Kleinemonde estuaries add to the growing body of evidence that the estuarine pipefish has been extirpated from these locations and is now only found in two estuarine systems. The occurrence of S. watermeyeri was found to be highly dependent on the cover of submerged macrophytes such as Zostera capensis (eelgrass). By providing a more complete picture of the conservation status of this critically endangered species, this work facilitates the development of a long‐term monitoring program and the identification of priority conservation areas. Abstract : This research aimed to determine priority areas for the conservation of the critically endangered estuarine pipefish using eDNA, and compare this with conventional seine netting and historical records. We designed an assay that detected the estuarine pipefish at more than four times (66.7%) the number of sites than traditional seine netting (16.7%). Our results confirm that local extinctions have occurred in the species' former range, and it is now found in just two estuarine systems (Kariega and Bushmans).