Estimation of paddlefish (Polyodon spathulaWalbaum, 1792) spawning habitat availability with consumer-grade sonar

Abstract

Summary The paddlefish (Polyodon spathula Walbaum, 1792) is a springtime migrant that requires discrete abiotic conditions such as water temperature, discharge, and substrate composition for successful spawning and recruitment. Although population declines have prevailed throughout much of the species range, Oklahoma paddlefish are abundant and support popular recreational snag fisheries – most notably in Grand Lake. This stock utilizes the Grand Lake's two primary headwaters, the Neosho and Spring rivers, with only episodic recruitment success. However, relationships between suitable spawning habitat and water level have not been evaluated in this system. Using consumer‐grade sonar equipment, this study identified and quantified hard river substrates (such as cobble and bedrock) and investigated proportional habitat availability at a variety of simulated river conditions. Sonar data were used to construct 49‐m2 grids of depth and bottom hardness (H) ranging from 0.0 (soft) ‐ 0.5 (hard). Ground‐truthing samples of bottom composition were collected with a grab sampler and by visual identification. Substrate types were pooled into two categories: soft substrates (H < 0.386) and spawning substrates (H ≥ 0.386) allowing for estimation of available spawning habitat in each river. Spawning habitat comprised 69% of total available habitat for the Neosho River (6.5 ha/km) and 58% for the Spring River (7.9 ha/km). Estimated spawning habitat was simulated over a range of river stages and predictive models were developed to estimate proportional spawning habitat availability (PHA). Although the Spring River contains more concentrated spawning habitat in closer proximity to Grand Lake, the Neosho River contains a greater quantity over nearly twice the distance to the first migration barrier, has a larger watershed, and demonstrates greater PHA at lower river stages. Model results were validated in context of known high and low recruitment years, where a greater frequency and duration of days with ≥90% PHA were observed in good recruitment years, particularly in the Neosho River. In total, results suggest the Neosho River has greater value for paddlefish reproduction than the Spring River. Research‐informed harvest management will remain critical to the conservation of wild‐recruiting stocks for continued recreational use in Oklahoma.

Accuracy and Precision of Low-Cost Echosounder and Automated Data Processing Software for Habitat Mapping in a Large River

“…The resulting river bottom hardness values exhibited little variance and the value was high (hard category: 0.4-0.5) at most of the measuring points. Previous studies conducted in lakes have shown a wider range of EcoSound hardness values and the output has been successfully used to determine different bottom types [36,39,40]. The softest values were recorded on "muck", mud, and silt [39,40], which were mostly missing on our study area.…”

“…Previous studies conducted in lakes have shown a wider range of EcoSound hardness values and the output has been successfully used to determine different bottom types [36,39,40]. The softest values were recorded on "muck", mud, and silt [39,40], which were mostly missing on our study area. Most of the silt/clay bottoms in our study area were located in the near-shore areas where depth was preventive of the use of the EcoSound method, and therefore the amount of data collected was lower in that substrate size class.…”

“…Low-cost and easy-to-use mapping tools are of interest to researchers, aquatic resource managers, and non-government conservation organizations, as they may allow a user to create basic maps of key aquatic parameters without special skills and without the need for expensive or specific data processing tools. For example, maps produced using EcoSound have been used for assessing and monitoring vegetation biomass [28,35,[37][38][39], estimating fish habitat availability [36,40], and as supportive material in many research and monitoring reports [39,[41][42][43].…”

Spatial sampling bias and model complexity in stream‐based species distribution models: A case study of Paddlefish (Polyodon spathula) in the Arkansas River basin, USA

“…For example, Oologah Lake on the Verdigris River was stocked from 1995 to 2000 and has since shown signs of natural recruitment, whereas Lake Texoma on the Red River (outside our study area) was stocked from 1997 to 2007 but has not evidenced natural recruitment (Patterson, , J. Schooley, ODWC, personal communication). The exact mechanisms behind this variation in restoration success remain unknown, but the hydrology and availability of suitable spawning habitat in upstream tributaries is considered key (Patterson, ; Paukert & Fisher, ; Schooley & Neely, ). Our ensemble map provided a visualization of stream reaches that were estimated as suitable for paddlefish.…”

Spawning Migration Periodicity and River Choice of the Grand Lake Stock of Paddlefish Polyodon spathula

“…Effective management of paddlefish (Polyodon spathula), an ancient river-spawning species native to the central United States (Gengerke 1986;Bettoli, Kerns, and Scholten 2009), is predicated on understanding the reproduction and patterns of movements of this highly mobile, migratory species (Russell 1986;Jennings and Zigler 2000;Scarnecchia et al 2007). Many aspects of the species' upriver spawning migrations and reproductive success are influenced by interannual variations in riverine habitat quantity and quality (Braaten, Fuller, and Lott 2009;Schooley and Neely 2018;Tripp, Neely, and Hoxmeier 2019). Interannual variations in river conditions also influence less directed, non-spawning movements of stocks (Southall and Hubert 1984;Moen, Scarnecchia, and Ramsey 1992;Tripp, Neely, and Hoxmeier 2019).…”