Population Dynamics and Simulated Effects of Length‐Based Trophy Regulations for Flathead and Channel Catfish in the Lower James River, South Dakota

Abstract

Catfish are popular with anglers fishing southeastern South Dakota rivers, and a group of anglers has expressed concern about the perceived overharvest of trophy‐size catfish. However, existing data are insufficient for determining whether Flathead Catfish Pylodictis olivaris and Channel Catfish Ictalurus punctatus are being overharvested. Our objective was to determine the population dynamics of Flathead and Channel catfish and model potential outcomes of length‐based trophy regulations (one fish and no fish harvested over 610 mm) in the lower James River, South Dakota. Multiple gears were used to collect Flathead Catfish (low‐frequency electrofishing and trotlines) and Channel Catfish (baited hoop nets and low‐frequency electrofishing) during 2018, and samples were augmented with angler‐caught catfish collected from three angling tournaments. Pectoral spines were removed from a subsample of fish for age estimation; 305‐mm and larger fish received a Carlin dangler tag with a reward value of US$0, $10, or $100. Growth rates were slow to moderate for Flathead Catfish and moderate for Channel Catfish. Trophy‐size Flathead Catfish (TL ≥ 1,020 mm) were sampled, but few of the collected Channel Catfish exceeded preferred length (TL ≥ 610 mm). Total annual mortality was estimated at 25.7% for Flathead Catfish and 25.2% for Channel Catfish. Exploitation estimated from angler reward tag returns was less than 1% for each species. Yield‐per‐recruit models indicated that a regulation specifying one fish over 610 mm would slightly reduce yield for both species but would only increase the number of memorable‐length Flathead Catfish (860 mm) and Channel Catfish (710 mm) by less than 1%. A no‐harvest regulation would substantially reduce yield of Flathead Catfish and would increase the number of memorable‐length Flathead Catfish by approximately 2% and Channel Catfish by less than 1%. Information obtained during this study suggests that current Flathead and Channel Catfish populations have limited trophy potential and that length‐based trophy regulations would have limited impact on the abundance of large catfish in the lower James River.

Two Decades of Advancement in Flathead Catfish Research

“…Annual exploitation rates in rivers range from 4.5% to 19.0% (Schall and Lucchesi 2021;Winders and McMullen 2021), and those in reservoirs range from 0% to 13% (Marshall et al 2009a;Sullivan and Vining 2011;Travnichek 2011a;Bodine et al 2016). These low annual mortality and exploitation rates are consistent with longlived species (e.g., 34 years as reported by Marshall et al 2009b), and this further suggests that overharvest is possible if angling pressure is high in a given location.…”

“…2006; Makinster and Paukert 2008; Hamel et al. 2021; Schall and Lucchesi 2021), from 0.11 to 0.40 in reservoirs (Winkelman 2011; Stubbs et al. 2015; Lucchesi et al.…”

“…Annual exploitation rates in rivers range from 4.5% to 19.0% (Schall and Lucchesi 2021; Winders and McMullen 2021), and those in reservoirs range from 0% to 13% (Marshall et al. 2009a; Sullivan and Vining 2011; Travnichek 2011a; Bodine et al.…”

“…Flathead Catfish populations that have been studied in the past two decades have low total mortality rates and are lightly exploited. Annual total mortality rates (A) of Flathead Catfish typically range from 0.14 to 0.62 in rivers where they are native (Willenberg 2000*;Daugherty and Sutton 2005c;Sakaris et al 2006;Makinster and Paukert 2008;Hamel et al 2021;Schall and Lucchesi 2021), from 0.11 to 0.40 in reservoirs (Winkelman 2011;Stubbs et al 2015;Lucchesi et al 2017;Muhlbauer and Krogman 2021), and from 0.16 to 0.37 in rivers where they have been introduced (Kwak et al 2006;Sakaris et al 2006;Kaeser et al 2011;Rachels and Ricks 2015;Bonvechio et al 2016;Hilling et al 2019). One exception is the Satilla River, Georgia, where A was reported as 0.62 (Bonvechio et al 2016) and 0.45 (Sakaris et al 2006), presumably due to the years of electrofishing removals conducted in this system.…”

Catfish 2020, A Clear Vision of the Future

“…For Iowa reservoirs, researchers suggested that a protected slot length limit or a maximum length limit would increase the size structure of Flathead Catfish populations (Muhlbauer and Krogman 2021, this special issue). Conversely, restrictive harvest regulations may not be successful in the development of trophy Flathead Catfish fisheries when slow growth and high natural mortality prevent individuals from reaching trophy sizes (Schall and Lucchesi 2021, this special issue). An increased minimum length limit was suggested to increase abundance of large Blue Catfish without reducing yield in a Missouri population characterized by slow growth (Michaletz et al.…”