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Photographs of Wading Bird Depredation Update Invasion Extent of Monopterus albus (Asian Swamp Eel)
Andrew T. Taylor, Henning von Schmeling, and James M. Long

Southeastern Naturalist, Volume 17, Issue 4 (2018): N72–N76

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2018 Southeastern Naturalist Notes Vol. 17, No. 4 N72 A.T. Taylor, H. von Schmeling, and J.M. Long Photographs of Wading Bird Depredation Update Invasion Extent of Monopterus albus (Asian Swamp Eel) Andrew T. Taylor1,*, Henning von Schmeling2, and James M. Long3 Abstract - Several anecdotes exist of wading birds depredating invasive Monopterus albus (Asian Swamp Eel) in waterways of the conterminous US. We present photographic evidence of 4 different wading bird species depredating adult Asian Swamp Eels in Georgia and Florida herein. Photographs taken by wildlife enthusiasts could provide a means for early detection of the Asian Swamp Eel and other aquatic species that are challenging to detect in waterways. Introduction. Several wild populations of Monopterus albus (Zuiew) (Asian Swamp Eel; hereafter, ASE) have been established in the conterminous US, often as a result of fish purposefully released from live-food markets (Nico et al. 2011). In Georgia, ASE was first documented in the early 1990s from ponds at the Chattahoochee Nature Center (CNC), Roswell, GA, and the species has since expanded in nearby marshes adjoining the Chattahoochee River within the Chattahoochee River National Recreation Area (CRNA) (Freeman et al. 2005, Johnson 2017). In the late 1990s, 3 established populations of ASE were reported in Florida: 1 near Tampa, another near Miami, and a third near Homestead and Everglades National Park (ENP; Collins et al. 2002, Shafland et al. 2010). Since 2008, observations of ASE have been reported from New Jersey, New York, Michigan, Texas, and an additional location in Georgia (USGS 2018), raising concerns about additional successful invasions and documenting areas invaded by the species. Native to tropical and temperate regions of Asia, ASE frequently occupy shallow vegetated habitats and burrow into muddy substrates, even withstanding temporary habitat desiccation (Liem 1967, Rosen and Greenwood 1976). Shallow, highly vegetated, and temporary habitats are often difficult to access and sample with conventional active fisheries gears (Hayes et al. 1996), and can lead to sampling biases associated with accessibility (sensu Balkenbush and Fisher 1997). For example, ASE are regularly reported from boat electrofishing of deeper, human-made canal systems in Florida (Kline et al. 2014, Shafland et al. 2010), whereas fewer records exist from interconnected shallow waters that are presumably ideal habitats for ASE (A.T. Taylor, H. von Schmeling, and J.M. Long, pers. observ.; USGS 2018). Thus, determining invasion extent of ASE can be challenging and plagued with uncertainty. Asian Swamp Eel and similar synbranchid eels are depredated by ichthyophagous wading birds in their native ranges (Ducommun and Beltzer 2010, Quiroga et al. 2013), and a quick web search revealed numerous photographs of such depredation events in Asia (e.g., Bird Ecology Study Group 2015, 2018). Anecdotes of North American wading birds depredating invasive ASE were reported in Georgia by Freeman et al. (2005) and in Florida by Shafland et al. (2010), but no photographic documentation was presented. Herein, we present 4 observations of wading bird depredation of ASE within US waterways and suggest that photographs taken by wildlife enthusiasts can provide important early detections of ASE invasion extent. 1Department of Natural Resource Ecology and Management, Oklahoma State University, Stillwater, OK 74078. 2Chattahoochee Nature Center, Roswell, GA 30076. 3US Geological Survey, Oklahoma Cooperative Fish and Wildlife Research Unit, Stillwater, OK 74078. *Corresponding author - Manuscript Editor: Nathan Dorn Notes of the Southeastern Naturalist, Issue 17/4, 2018 N73 2018 Southeastern Naturalist Notes Vol. 17, No. 4 A.T. Taylor, H. von Schmeling, and J.M. Long Observations. Four unique observations of wading bird depredation of ASE are presented, each documented by wildlife enthusiasts and depicting wading birds depredating ASE from heavily vegetated areas within or near shallow-water habitats. On 28 February 2009, a juvenile Egretta caerulea (L.) (Little Blue Heron) was photographed consuming an ASE in marsh habitats along the Anhinga Trail in ENP (EDDMapS 2009). A similar photograph was taken in 2013 along the Anhinga Trail of Mycteria americana (L.) (Wood Stork) depredating an ASE (NRC 2014). On 6 November 2016, Judd Patterson (Fort Lauderdale, FL) photographed an Ardea alba (L.) (Great Egret) consuming an ASE along a roadside, ~3 km northwest of the Anhinga Trail (Fig. 1; iNaturalist 2016). On 19 December 2017, Linda Marchetti (Roswell, GA) photographed an Ardea herodias (L.) (Great Blue Heron) consuming an ASE in marsh habitats of the Chattahoochee River situated upstream of the CNC (Fig. 2). Discussion. These observations verified that at least 4 species of ichthyophagous wading birds depredate ASE in the conterminous US, and 2 provided early detection of ASE range expansion. The Anhinga Trail photograph in 2009 was one of the first records of the northward expansion of ASE within ENP (Kline et al. 2014). The Chattahoochee River marsh photograph in 2017 represents the northernmost record of adult ASE in marsh habitats Figure 1. Great Egret depredation of Asian Swamp Eel in Everglades National Park near Homestead, Florida. Photograph © Judd Patterson. 2018 Southeastern Naturalist Notes Vol. 17, No. 4 N74 A.T. Taylor, H. von Schmeling, and J.M. Long Figure 2. Great Blue Heron depredation of Asian Swamp Eel in marsh habitats of the Chattahoochee River near Roswell, Georgia. Photographs © Linda Marchetti. N75 2018 Southeastern Naturalist Notes Vol. 17, No. 4 A.T. Taylor, H. von Schmeling, and J.M. Long despite several electrofishing surveys along the margins of this marsh in years prior to, and following, the observation (Freeman et al. 2005; Johnson 2017; A.T. Taylor, H. von Schmeling, and J.M. Long, unpubl. data). Managers tasked with monitoring invasive species often have limited resources to devote to surveying, yet cryptic species may require additional sampling effort and multiple sampling methods in order to best document range extent and expansion (Hoffman et al. 2011, Mehta et al. 2007). In some cases, information garnered from predators can help document invasive species that are otherwise difficult to detect with conventional sampling methods (e.g., Boucek and Rehage 2014). Wildlife enthusiasts, birdwatchers, and even amateur photographers could provide managers with early-detection data by observing and photographing ASE depredation by wading birds. A preliminary summary of the 2016 National Survey of Fishing, Hunting, and Wildlife-Associated Activities reported that there were ~45 million bird observers in the US, nearly equaling the number of hunters and anglers combined (USFWS 2017). Leveraging existing wildlife photography online and within citizen-science databases like iNaturalist and eBird could help update invasion extent; however, identifying ASE records from depredation photographs on the internet or in larger citizen-science databases is difficult unless photographs have metadata or other searchable text indicative of ASE depredation (e.g., iNaturalist 2016). Perhaps a better strategy would be to undertake focused, regional, citizen-science efforts to document range expansion in areas with established ASE populations, particularly in areas frequented by wildlife enthusiasts (e.g., parks like CNC, CRNA, and ENP). 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