American Fisheries Society Symposium 80:461–472, 2013 © 2013 by the American Fisheries Society Size-Based Mortality Caps as Thresholds for Managing Hybrid Striped Bass in Kansas Reservoirs

Abstract. — Total annual mortality and mortality caps (maximum mortality thresholds) were estimated for hybrid striped bass (striped bass Morone saxati-lis × white bass M. chrysops) populations sampled in six large Kansas reservoirs spanning 1995–2001; all reservoirs lacked a minimum length limit but had a 2/d creel limit. Total annual mortality of age-1 and older hybrid striped bass was estimated using a weighted catch curve. Mortality caps were modeled by varying growth rates and management objectives. Mortality rates that approach the cap signal the need for increased monitoring to determine what additional manage-ment action should be taken (e.g., harvest regulations to reduce mortality) or to reevaluate the size objective (targeted mean length of harvested fish) for the fishery. Estimated mortality caps were then compared with observed growth and mortality rates. Total annual mortality rates for all reservoirs varied from 22 % to 52 % (mean = 38%; SE = 4.9). All but two reservoirs had total annual mortality rates greater than 40%. Analysis of mortality caps indicated that when the objec-tive was to maintain the mean length of harvested hybrid striped bass at curren