Simulated effects of imperfect sterile sport fish stocking on persistence of fertile fish in new exploited populations

Abstract

AbstractObjectiveSterile fish are used for multiple purposes, including enhancing sport fisheries where reproduction is not wanted. In some regions with few native sport fish, but strong angler desire for nonnative piscivorous species, establishing new fisheries using sterile predators is being explored as a management option. In this context, objective information is needed to guide discussions with stakeholders and inform policy.MethodsArtificial induction of triploidy is commonly used to produce sterile predators, but the process is rarely 100% effective. Thus, starting a new triploid fishery would require stocking fish with imperfect induction, which carries the risk of jump‐starting a feral population if stocked diploids survive to maturity and become self‐sustaining. We developed a joint stochastic age‐structured model to explore the potential consequences of stocking triploid Walleye Sander vitreus with imperfect induction into locations devoid of diploids to inform stocking decisions.ResultModel simulations demonstrated that a high induction rate (≥95%) for triploid fingerling stocking combined with multiple simultaneous constraints on natural reproduction were required to minimize the probability of diploid Walleye persistence or to maintain the abundance of natural‐origin fish near or below expectations from stocking alone. Reproductive interference from triploid males could suppress the population expansion of diploids under some circumstances. Above patterns were also contingent on maintaining a relatively high annual mortality rate (>50%)—reflective of exploited populations—on age‐classes of Walleye particularly vulnerable to catch and harvest.ConclusionOur modeling framework provides decision makers objective information to weigh stocking options and guide discussions. A better understanding of the recruitment and exploitation dynamics of nonnative Walleye populations and the poststocking performance and behavior of triploid Walleye would help refine models and expectations.