AUTHORS: Benjamin J. Schall, South Dakota Department of Game, Fish and Parks; Lindsey A. P. LaBrie, USGS Cooperative Fish and Wildlife Unit, University of Arkansas; Tanner L. Carlson, Minnesota Department of Natural Resources; Jeff S. Wesner, University of South Dakota; Chelsey A. Pasbrig, South Dakota Department of Game, Fish and Parks; Steven R. Chipps, USGS Cooperative Fish and Wildlife Research Unit, South Dakota State University
ABSTRACT: Reproductive characteristics for populations of imperiled non-game species are not regularly studied but may be important for identifying factors associated with population sustainability. Understanding reproductive traits in vulnerable species, particularly long-lived species, may provide insight for implementing management actions to respond to changes in angling behavior. This study aimed to assess the reproductive characteristics of a stable population of long-lived Blue Suckers Cycleptus elongatus in the unchannelized Missouri River in South Dakota. We collected demographic information and gonads from 182 Blue Suckers in 2021-2022. We used Bayesian generalized linear mixed-effects models to assess length and weight relationships with gonadosomatic index (GSI) and fecundity and used spawning potential ratios (SPR) to model the influence of varying harvest and minimum length limit (MLL) scenarios. Fish lengths ranged from 560-821 mm. Female GSI increased with length to ~720 mm before declining, and male GSI remained consistent across lengths. Strong positive linear relationships were observed for GSI with fish weight and fecundity. Using recent natural mortality estimates for this population, SPR under current no-limit regulations decreases rapidly as fishing mortality (F) approached 0.10 but implementing a 660-mm MLL would prevent SPR from falling below acceptable limits (0.2-0.3) at F values as high as 0.69. This study demonstrates that reproductive data and SPR modeling can be used to provide length-based regulation recommendations for vulnerable, non-game species that receive less management focus.
