An Integrated Population Model for Harvest Management of Atlantic Brant

Abstract

Atlantic brant (Branta bernicla hrota) are important game birds in the Atlantic Flyway and several long‐term monitoring data sets could assist with harvest management, including a count‐based survey and demographic data. Considering their relative strengths and weaknesses, integrated analysis to these data would likely improve harvest management, but tools for integration have not yet been developed. Managers currently use an aerial count survey on the wintering grounds, the mid‐winter survey, to set harvest regulations. We developed an integrated population model (IPM) for Atlantic brant that uses multiple data sources to simultaneously estimate population abundance, survival, and productivity. The IPM abundance estimates for data from 1975–2018 were less variable than annual mid‐winter survey counts or Lincoln estimates, presumably reflecting better accounting for observer error and incorporation of demographic estimates by the IPM. Posterior estimates of adult survival were high (0.77–0.87), and harvest rates of adults and juveniles were positively correlated with more liberal hunting regulations (i.e., hunting days and the daily bag limit). Productivity was variable, with the percent of juveniles in the winter population ranging from 1% to >40%. We found no evidence for environmental relationships with productivity. Using IPM‐predicted population abundances rather than mid‐winter survey counts alone would have meant fewer annual changes to hunting regulations since 2004. Use of the IPM could improve harvest management for Atlantic brant by providing the ability to predict abundance before annual hunting regulations are set, and by providing more stable hunting regulations, with fewer annual changes. © 2021 The Wildlife Society.

Where east meets west: Phylogeography of the high Arctic North American brant goose

“…In contrast, the genetic structure observed in this study of North American brant is likely maintained by disjunct distributions across the annual cycle (Lewis et al., 2020 ) which restricts potential inter‐regional mating opportunities. The distinct regional separation in brant, while other species exhibit signatures of admixture, may be attributable to the relatively stable or declining population trends experienced in brant (Olson, 2021 ; Roberts et al., 2021 ; Sedinger et al., 2019 ) such that population densities have not changed sufficiently to influence dispersal decisions as in snow geese.…”

Population dynamics and harvest management of eastern mallards

“…Despite historical conditions, the current eastern North American landscape supports abundant mallards, and our work indicates a carrying capacity of over 1.3 million birds, with recently declining abundance. In harvest management, IPMs such as ours can help managers set abundance index thresholds that trigger changes in harvest regulations (Roberts et al 2021) or use estimates in an adaptive management program (Johnson et al 2014, USFWS 2019 a ). No matter the cause of the decline, or prospects to changing population trajectory, the use of this model in an eastern mallard harvest strategy provides a framework for population processes that can be used in its current form and improved as new information is obtained.…”

“…Waterfowl harvest strategies have increasingly relied on the use of integrated population models (IPMs), which link population count data and demographic parameters through a joint likelihood (Besbeas et al 2002, Schaub et al 2007, Arnold 2018). Harvest strategies for American black ducks ( Anas rubripes ; Conroy et al 2002, USFWS 2019 a ), Atlantic brant ( Branta bernicula hrota ; Roberts et al 2021), scaup ( Aythya spp. ; USFWS 2019 a ), and others rely on IPMs to obtain demographic estimates for use in making regulatory decisions.…”

Including a spatial predictive process in band recovery models improves inference for Lincoln estimates of animal abundance

“…Lincoln estimators (Lincoln, 1930) are increasingly used to estimate abundance at large scales (Alisauskas et al, 2009) by combining information on the rate and total number of individuals harvested; data that are typically obtained from band recoveries (Roberts et al, 2021) and hunter survey or harvest reporting. While historically underutilized, Lincoln estimators have been applied with great success in the management of multiple game species (Diefenbach et al, 2012;Hagen et al, 2014;Otis, 2006;Saunders et al, 2019), most notably for the harvest of waterfowl across North America (Alisauskas et al, 2014;Arnold et al, 2018).…”