Modeling the Responses of Alligator Gar Populations to Harvest under Various Length‐Based Regulations: Implications for Conservation and Management

Abstract

AbstractInterest in managing Alligator Gar Atractosteus spatula populations as a unique sport fishery has increased over the past decade, but despite this interest population responses to harvest are poorly understood. Fishing regulations for Alligator Gars vary throughout their distribution; however, to date most regulations have focused on a daily creel limit. We developed an age‐structured dynamic‐pool model in R to (1) quantify the population‐level effects of exploitation and (2) evaluate how these effects would be altered under a suite of length‐based fishing regulations. The model was parameterized based primarily on empirically estimated dynamic rates for Texas Alligator Gar populations. For each model scenario, we calculated the mean and variance of the number of trophy fish in the population, the population size, the spawning potential ratio, and the fishery yield over a 100‐year period. Alligator Gar populations were highly sensitive to exploitation in our model simulations. An exploitation rate of 7% caused the average population size to decline by 50%, and a rate of only 3% halved the number of trophy fish available in the population. Under no length restrictions, recruitment overfishing occurred above an exploitation rate of 6.5%, while yield was maximized at only 9% exploitation. Based on our model results, the use of length limits may provide some options for sustaining existing trophy Alligator Gar fisheries under increased effort and could allow anglers to catch and even harvest more trophy‐size fish. Given the sensitivity of long‐lived periodic life history strategists to exploitation and the benefits that length‐based regulations can provide, we encourage managers to consider such regulations to increase resilience to exploitation and improve fishery quality.