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733 Double-Crested Cormorants in the Laurentian Great Lakes: Issues and Ecosystems Mark S. Ridgway and David G. Fielder The debate concerning the effects of cormorant (Phalacrocorax spp.) consumption on fish abundance shows a remarkable degree of fidelity to a common theme independent of location, language, or cultural heritage. The scope of this debate stems largely from population increase and expansion of the Great Cormorant(Phalacrocorax carbo)inEurope(Bregnballeetal.2003)andJapan(Kamedaetal.2003)andthe Double-Crested Cormorant (P. auritus) in North America (Weseloh et al. 1995), including a return to earlier high abundance in some areas of North America (Wires and Cuthbert 2006). Debate develops between those interested in allocation of fish production and a corresponding skepticism by others, regarding the significance of cormorant predation on fish populations or the possibility that cormorant populations are returning to historical abundance and distribution. A similar debate occurs in the case of impacts on other colonial nesting waterbirds, stemming from increasing Double-Crested Cormorant populations or whether restoration of vegetation lost due to damage from nesting Double-Crested Cormorants warrants management action (Cuthbert et al. 2002; Farquhar et al. 2003; Hebert et al. 2005). Callsforactionbyrecreationalandcommercialfishers,basedontherealorperceivedroleofcormorants in affecting fish abundance, have followed the population trajectory of the species. More than thirty years ago, there was interest by biologists and policy makers in ensuring the recovery of cormorant populations at very low levels because of human persecution and/or contaminant effects (e.g., DDT in the Great Lakes; Weseloh et al. 2002). Cormorant populations began to increase, following implementation of policies and legislation that restricted pesticide use and protected nesting bird populations in Europe and North America.TheresurgenceofDouble-CrestedCormorantsintheGreatLakeswaslikelyfueledbythepresence of the exotic Alewife (Alosa pseudoharengus) within their breeding grounds, which provided an abundant nearshorepreyresourcetothebirdsduringnestingthatwasnotoriginallypresentinmid-twentiethcentury, when coregonines (e.g., Cisco [Coregonus artedi]) dominated the pelagic and nearshore planktivore community . Alewife may have enabled Double-Crested Cormorants to recover to numbers greater than were historically present in the Great Lakes. Recent declines in nesting Double-Crested Cormorants on Lake Huron parallel recent declines in Alewife (Dunlop et al. 2010; Ridgway 2010b). Also in North America, large-scaledevelopmentofaquacultureproductionfacilitiesprovidednewfoodsourcesforDouble-Crested Mark S. Ridgway and David G. Fielder 734 Cormorants in their southern winter range (Glahn and Brugger 1995; Glahn and Stickley 1995) and have likely contributed to recent population expansion on their breeding grounds (Hebert et al. 2008). A common feature of cormorant population growth in North America and Europe has been a phase of exponential increase in nest counts soon after breeding colony establishment (Weseloh et al. 1995, 2002; Bregnballe et al 2003). Accelerating rates of increase in cormorant populations led to complaints, by commercial and recreational fishers, that local fish abundance was adversely affected by cormorant predation. Demands for management of cormorant populations have been met with opposing views of non-intervention or lack of evidence of effects (e.g., Reed et al. 2003). These include appeals to historic records from the period of European colonization of North America to recover evidence on the previous state of cormorant populations prior to their reduction during the twentieth century (Wires and Cuthbert 2006). Although the timing of cormorant recovery in Europe and North America varied within and among regions, there is a general pattern of population recovery starting in the 1970s and 1980s, followed by increasing demands for population reduction, as a result of perceived threats to fisheries. Biologists and policy makers would recognize this description of the trend on the “cormorant issue” for any given location anywhere in the world. We might, therefore, expect common policy questions and responses to the cormorant issue among North American and European agencies. Recognition of these common features by Europeans and North Americans involved in this issue was summarized with the label “bête noir” (“black beast”), as a caricature for the species, intensity of debate, scale of fieldwork needed to demonstrate effects, and difficult choices needed to resolve this resource management issue (Wires et al. 2003). With respect to the Laurentian Great Lakes, there may be no other resource management issue in recent memory that matches in focus and intensity the debate regarding the role of Double-Crested Cormorants in coastal food webs. Because of this, a proposal has been made to incorporate waterbirds into the ecosystem-based management of the Great Lakes (Hebert and Sprules 2002). Prior to the current technical and policy challenges on the cormorant issue, a cultural image of cormorants was long ago distilled by John Milton, in his epic poem of 1674, Paradise Lost...

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