Tools and Technology Article Using 2 Genetic Markers to Discriminate Among Canada Goose Populations in Ohio KRISTIN A. MYLECRAINE, 1 Ohio Division of Wildlife, Olentangy Wildlife Research Station, Ashley, OH 43015, USA; and Department of Evolution, Ecology and Organismal Biology, The Ohio State University, Columbus, OH 43210, USA H. LISLE GIBBS, Department of Evolution, Ecology and Organismal Biology, The Ohio State University, Columbus, OH 43210, USA CHRISTINE S. ANDERSON, Department of Evolution, Ecology and Organismal Biology, The Ohio State University, Columbus, OH 43210, USA MARK C. SHIELDCASTLE, Ohio Division of Wildlife, Crane Creek Wildlife Research Station, Oak Harbor, OH 43449, USA ABSTRACT Canada goose (Branta canadensis) harvest management depends on reliable estimates of harvest composition, and established genetic methods provide an alternative to traditional methods. We expanded upon previous genetic studies by comparing the utility of 6 nuclear microsatellite loci and mitochondrial (mtDNA) control region sequences for discriminating among giant (B. c. maxima) and interior (B. c. interior) populations in Ohio (USA) Canada goose harvests at both individual and population levels. Subspecies and populations exhibited greater differentiation in mtDNA (F ST ¼ 0.202) than microsatellites (F ST ¼ 0.021), as would be expected based on differences in effective population size. Neither microsatellites nor mtDNA alone were sufficient for estimating harvest composition at the subspecies or population level in simulations and empirical blind tests using individuals of known origin; however, a combined microsatellite þ mtDNA dataset yielded accurate and precise harvest derivations at the subspecies level. Both population-level mixed stock analysis and individual-level assignment tests provided accurate results, but a large proportion of birds could not be assigned with confidence at the individual level. We applied mixed stock analysis and the combined microsatellite þ mtDNA dataset to Ohio’s 2003–2004 harvest and found that interior populations accounted for 4.9% (95% CI ¼ 1.7–8.0%) of the statewide early season and 9.3% (95% CI ¼ 6.9–11.6%) of the regular and late-season harvested sample. These results suggest that maximum likelihood harvest derivations are highly dependent on the choice of genetic markers. Studies should only employ markers that exhibit sufficient variation and have been shown through simulations and empirical testing to accurately discriminate among the subspecies or management populations of interest. ( JOURNAL OF WILDLIFE MANAGEMENT 72(5):1220–1230; 2008) DOI: 10.2193/2007-116 KEY WORDS Branta canadensis, genetic stock identification, giant Canada goose, harvest derivation, harvest management, interior Canada goose, microsatellite DNA, mixed stock analysis, mtDNA. Canada geese (Branta canadensis) have a complicated taxonomy, with 6 subspecies currently recognized (Delacour 1954, Banks et al. 2004). Subspecies can be grouped into those exhibiting long migrations to breed in Arctic and subarctic regions of North America (subarctic-nesting) or those breeding in southern Canada and the United States (temperate-nesting). For harvest management purposes, Canada geese are further divided into a number of management populations; in many cases, one subspecies contains multiple management populations, each represent- ing a discrete breeding population. Harvest management attempts to maintain a desirable and sustainable level of harvest, while ensuring viability of all management pop- ulations and maintaining these populations at or near their objective population sizes (North American Waterfowl Management Plan Committee 2004), but this is compli- cated by the co-occurrence of birds from multiple breeding populations during autumn and winter hunting seasons. Of the 4 management populations of Canada geese affiliated with the Mississippi Flyway, 3 occur regularly in Ohio harvests (T. Moser, United States Fish and Wildlife Service [USFWS], unpublished data). These include two subarctic-nesting populations of the interior subspecies (B. c. interior) and one temperate-nesting population of the giant subspecies (B. c. maxima). The Southern James Bay Population (SJBP; B. c. interior) breeds on Akimiski Island and in the Hudson Bay Lowlands to the west and south of James Bay, and winters from southern Ontario (Canada) and Michigan to Mississippi, Alabama, and South Carolina (USA). The Mississippi Valley Population (MVP; B. c. interior) breeds in northern Ontario in the Hudson Bay Lowlands, west of James Bay and south of Hudson Bay, and winters primarily in Wisconsin, Illinois, and Michigan (USA). Both interior populations have fluctuated, but remained fairly stable, and are currently at or above their population objectives of 100,000 SJBP and 375,000 MVP geese (USFWS 2007). The Mississippi Flyway Giant Population (MFGP; B. c. maxima) has been reestablished in all Mississippi Flyway states, and continues to increase, with a current population of 1.6 million (USFWS 2007). Due to discrete interior and giant breeding ranges and high levels of individual philopatry, potential interbreeding between subspecies is unlikely; however, movement between SJBP and MVP management populations has been observed (Leafloor 1998). Harvest management in Ohio aims to maximize harvest of MFGP geese to control this population and provide recreational opportunities, while limiting the harvest of SJBP and MVP geese. An understanding of the spatial and temporal variation in harvest composition is necessary to identify the appropriate management options to accomplish these goals. Genetic techniques provide a viable alternative to traditional methods of estimating harvest derivations, such as band recovery analyses and morphometric discrim- ination (Pearce et al. 2000, Inman et al. 2003, Scribner et al. 1 E-mail: kristin.mylecraine@dnr.state.oh.us 1220 The Journal of Wildlife Management  72(5)