White bass (Morone chrysops) are a popular sport fish throughout most of their zoogeographic distribution. We conducted a population assessment of white bass in Pool 4 of the Arkansas River. Using population metrics calculated from the assessment, responses of the white bass fishery to a 254-mm or 305-mm minimum length limit (MLL) were simulated using the Fishery Analysis and Modeling Simulator (FAMS) model. White bass ages ranged from 1-7, but 88% of white bass were less than age 5. Conditional natural mortality averaged 0.43, and total annual mortality was 54%, so exploitation was estimated to be 0.15. Implementation of a 254-mm MLL would reduce the number of fish harvested by 18%-32%, but increase the average weight of harvested fish by 21%-43%. Yield was predicted to increase or decrease by 10% depending upon natural mortality and exploitation. The portion of the cohort reaching preferred size (300 mm TL) ranged from 5% to 26%. Implementation of a 305-mm MLL was predicted to decrease the number of fish harvested by anglers by 37%-60% but increase average weight of harvested fish by 47%-101%. Change in yield ranged from -30% to 12%, but the percent of preferred-sized white bass in the populations was predicted to increase 14%-86%. The Arkansas River white bass population was characterized by low exploitation, moderately high natural mortality, and moderate growth rates. Yield is unlikely to change much under a minimum length limit, but size structure could be improved.
