University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln USDA National Wildlife Research Center - Staff U.S. Department of Agriculture: Animal and Publications Plant Health Inspection Service Spring 2012 Management of double-crested cormorants to improve sport fi sheries in Michigan: three case studies Brian S. Dorr USDA/APHIS/WS National Wildlife Research Center, [email protected] Shauna L. Hanisch Michigan State University Peter H. Butchko U.S. Department of Agriculture David G. Fielder Michigan Department of Natural Resources, [email protected] Follow this and additional works at: https://digitalcommons.unl.edu/icwdm_usdanwrc Dorr, Brian S.; Hanisch, Shauna L.; Butchko, Peter H.; and Fielder, David G., "Management of double- crested cormorants to improve sport fi sheries in Michigan: three case studies" (2012). USDA National Wildlife Research Center - Staff Publications. 1123. https://digitalcommons.unl.edu/icwdm_usdanwrc/1123 This Article is brought to you for free and open access by the U.S. Department of Agriculture: Animal and Plant Health Inspection Service at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in USDA National Wildlife Research Center - Staff Publications by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Human–Wildlife Interactions 6(1):155–168, Spring 2012 Management of double-crested cormorants to improve sport fi sheries in Michigan: three case studies BRIAN S. DORR, U.S. Department of Agriculture, Wildlife Services’ National Wildlife Research Center, Mississippi Field Station, P.O. Box 6099, Mississippi State, MS 39762, USA brian.s.dorr@ aphis.usda.gov. SHAUNA L. HANISCH, Michigan State University, Department of Fisheries and Wildlife, 13 Natural Resources, East Lansing, MI 48824, USA PETER H. BUTCHKO, U.S. Department of Agriculture, Wildlife Services, 2803 Jolly Road, Suite 100, Okemos, MI 48864, USA. DAVID G. FIELDER, Michigan Department of Natural Resources, Alpena Fisheries Research Sta- tion, 160 E. Fletcher, Alpena, MI 49707, USA Abstract: Impacts of double-crested cormorants (Phalacrocorax auritus) to fi sheries have been documented, but evaluation of the process and outcomes of cormorant management to reduce impacts on fi sheries is lacking. We provide a synthesis of adaptive management of double-crested cormorants in the Les Cheneaux Islands (LCI), Brevoort Lake, and Drummond Island, Michigan from 2004 to 2007. The LCI management focused on reducing numbers of nesting cormorants in the region as a means of improving the yellow perch (Perca fl avescens) population and fi shery. At Brevoort Lake and Drummond Island, management focused on lethal and nonlethal harassment of spring migrating cormorants to reduce their foraging on spawning walleye (Sander vitreus) and yellow perch and to improve those fi sheries and increase fi sh populations. At each location, management efforts reduced cormorant foraging, and fi shery data indicated increased abundance of sport fi sh species. The 3 locations combined provided evidence for the underlying hypotheses that cormorants can infl uence mortality of local sport fi sh populations and that short-term management goals have been met. Continuation of adaptive management and monitoring programs will determine whether the improvement of targeted sport fi sheries through cormorant management is sustainable. Key words: adaptive management, cormorants, culling, fi sheries, harassment, human– wildlife confl icts, predation Populations of the double-crested prior to and concurrent with management cormorant (Phalacrocorax auritus; hereaft er, actions. cormorant) increased substantially throughout In the United States, nearly all bird species are the 1980s and 1990s, most notably in the eastern protected by the Migratory Bird Treaty Act of United States and Canada and the Great Lakes 1918, and the conservation of their populations (Hatch and Weseloh 1999, Wires et al. 2001). is a responsibility of the U.S. Fish and Wildlife Corresponding to this increase in numbers Service (USFWS). The USFWS revisited its were increases in the level of concern over policy for cormorant management when the real and potential damages associated with increasing abundance of cormorants and cormorants (Taylor and Dorr 2003). A growing concomitant upward trend in resource confl icts body of evidence in the United States and brought them to the forefront of migratory bird Canada demonstrates the reality of impacts management priorities. In keeping with the that abundant cormorant populations can have National Environmental Policy Act, the USFWS on their environment (Shieldcastle and Martin and the U.S. Department of Agriculture, Wildlife 1999, Taylor and Dorr 2003, Rudstam et al. 2004, Services (WS) cooperated on the development Hebert et al. 2005, Fielder 2008). The degree of an environmental impact statement (EIS) to of signifi cance for all categories of resource address the environmental eff ects of potential damages (e.g., ecological, economic, and policy revisions. In August 2003, aft er 4 years, 22 aesthetic) associated with cormorants varies public meetings, and >12,000 public comments, considerably from site to site. This variability in the USFWS published the fi nal EIS (USFWS actual and perceived impacts is the impetus for 2003a). much of the need for research and evaluation The most signifi cant regulatory change that 156 Human–Wildlife Interactions 6(1) came out of the fi nal EIS was the public resource depredation order (PRDO). This regulation authorizes offi cials of state wildlife agencies, WS, and Native Les Cheneaux Islands American tribes to control cormorants to protect fi sh, wildlife, plants, and their habitat in 24 states, including Michigan (USFWS 2003b). The PRDO’s purpose is to protect natural resources that are managed by public agencies for public benefi t (USFWS 2003b). The fi rst year of im- Figure 1. Les Cheneaux Islands archipelago of northern Lake Huron, Michigan, site of cormorant breeding colony management from 2004 to plementation of the PRDO 2007. Brevoort Lake and Drummond Island, Michigan, sites of spring on the northern breeding harassment of double-crested cormorants evaluated in 2005-2007 and grounds occurred in 2004 2004–2007, respectively. in New York, Vermont, and Michigan. In this Islands (LCI), Brevoort Lake, and Drummond paper, we discuss the cormorant management, Island, Michigan (Figure 1). monitoring, and research activities conducted by the WS program in Michigan (WS-MI), WS, Background and methods National Wildlife Research Center (NWRC), Les Cheneaux Islands Michigan Department of Natural Resources Cormorants have made a remarkable (MDNR), U.S. Forest Service (USFS), U. S. comeback in Michigan since they were placed Geological Survey (USGS), and Lake Superior on the state’s endangered species list in 1976 State University from 2004 to 2007. We evaluate (MDNR 2005). By 1986, >1,000 cormorant nests management actions in an adaptive format were documented in the state (MDNR 2005). By (Holling 1978, Walters 1986, Lee 1993) to link 1997, Wires et al. (2001) estimated Michigan’s learning with policy and implementation. cormorant abundance at > 30,000 breeding pairs. Specifi cally, we focus on research and The LCI population trend mirrors that of the state management eff orts in the Les Cheneaux as a whole. In 1980, cormorants established the Figure 2. Number of nesting pairs of cormorants in the Les Cheneaux Islands, Michigan, 1980–2007. The vertical line indicates when control activities began. Cormorants • Dorr et al. 157 fi rst colony in the western part of the LCI at St. accounted for the contin-ued high total annual Martins Shoal (Diana et al. 1997). Cormorant mortality rate. Fielder (2008) concluded that numbers in the LCI increased nearly 6-fold from cormorant predation explained the greatest the early 1990s to a local breeding population of amount of variation in yellow perch abundance >5,500 nests in 2002 (Figure 2). of the explanatory factors evaluated. Wildlife The LCI is an archipelago of at least 23 named Services–Michigan (WS–MI) implemented a islands, located in northern Lake Huron. cormorant damage management program in Since the early 1900s, the yellow perch (Perca the spring of 2004, in light of the substantiation fl avescens) fi shery has been one of the main of fi shery and fi sh population declines for natural resources att racting visitors to the LCI the LCI and in response to stakeholder (Diana et al. 1987, Fielder 2008). Starting in concern (Dorr et al. 2010a, Fielder 2010). the late 1970s, the LCI yellow perch fi shery underwent a decline, remained relatively stable Drummond Island and Brevoort Lake through the mid-1990s, then fell to the point of Fielder et al. (2007) made community near total collapse in 2000 (Fielder 2004, Fielder assessments of fi sh communities in the St. 2008). Many residents of communities in the Mary’s River from 1975 to 2006 (including region believed that increasing cormorant Potagannissing Bay, which is adjacent to numbers were the cause of the yellow perch Drummond Island and the source of the crash, given the simultaneous decline and Potagannissing River; Figure 1). A 2002 study collapse of the fi shery and the signifi cant revealed that yellow perch and walleye (Sander increase in the abundance of nesting cormorants vitreus) abundance in Potagannissing Bay had in the LCI (Diana et al. 1987, Belyea et al. 1999, declined relative to previous surveys (Fielder et Fielder 2004). al. 2003). While not defi nitive, the fi