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Two Significant Records of Exotic Tropical Freshwater Fishes in Southern Alabama
James C. Godwin, David A. Steen, David Werneke, and Jonathan W. Armbruster

Southeastern Naturalist, Volume 15, Issue 4 (2016): N57–N60

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N57 2016 Southeastern Naturalist Notes Vol. 15, No. 4 J.C. Godwin, D.A. Steen, D. Werneke, and J.W. Armbruster Two Significant Records of Exotic Tropical Freshwater Fishes in Southern Alabama James C. Godwin1,*, David A. Steen1, 2, David Werneke2, and Jonathan W. Armbruster2 Abstract - Incidental observations of aquatic exotic species may represent important early indicators of established populations. Herein we report ecologically significant observations of 2 exotic fish taxa in southern Alabama—Pterygoplichthys disjunctivus x pardalis (Amazon Sailfin Catfish) and Oreochromis niloticus (Nile Tilapia). Our observations establish the presence and confirm reproduction, respectively, of these species in the state. Aquatic exotic species have become established throughout much of the southeastern United States (Nico and Fuller 1999) and they contribute to the tremendous ecological and economic impacts of nonindigenous introductions in this country (Pimentel et al. 2000, Ricciardi and Rasmussen 1999). For example, exotic species may contribute to the relatively high rates of aquatic species extinctions in the region (Gurevitch and Padilla 2004, Wilcove et al. 1998). The primary means of introduction for exotic fishes in the southeastern US include the pet trade and aquaculture. Early detection of potentially invasive species in a given area is extremely important when designing plans to manage them (Holden et al. 2016), but systematic surveys are rarely completed. Therefore, incidental encounters of exotic species suggest the presence of established populations and might stimulate additional surveys. In 2014, we conducted a mark–recapture study of turtles in Baldwin and Mobile counties, Alabama. To trap turtles, we used hoop nets with lead lines (trammels) with the intervening trammel-net functioning as a drift fence to intercept and direct turtles into the unbaited hoop nets. Hoop nets were 1.2 m in diameter and double-throated (i.e., with a pair of internal funnels). We focused our trapping efforts in shallow, muddy-bottomed, tidally influenced rivers; the riparian vegetation in the areas where we trapped ranged from broad, open marshes to shrub–tree zones. During turtle trapping, we recorded 2 exotic fish species as bycatch that represent ecologically significant observations for Alabama (Table 1), including Pterygoplichthys disjunctivus Weber x pardalis Castelnau (hybrid Sailfin Catfish; Fig. 1) and Oreochromis niloticus L. (Nile Tilapia) brooding eggs. Herein we provide information on these captures as well as relevant information previously reported in the nonindigenous aquatic species database maintained by the US Geological Survey (2016). The nearest previously reported record of P. disjunctivus to our capture site was observed in the Pearl River near Jackson, MS, in 1992 (USGS 2016). The nearest P. pardalis record to our study site is from 2009 in central Florida, and that specimen was identified as Pterygoplichthys based on having >7 branched dorsal-fin rays and no hypertrophied odontodes on the cheek per Armbruster (2004) and via the key in Armbruster and Page (2006). There are numerous additional records of that species from southern Florida (USGS 2016). In 2007, two specimens of O. niloticus were reported from the Weeks Bay watershed where we captured our animal (USGS 2016); several other specimens have been collected 1Alabama Natural Heritage Program and Auburn University Museum of Natural History, Auburn University, Auburn, AL 36849. 2Department of Biological Sciences and Auburn University Museum of Natural History, Auburn University, Auburn, AL 36849. *Corresponding author - Manuscript Editor: Nathan Franssen Notes of the Southeastern Naturalist, Issue 15/4, 2016 2016 Southeastern Naturalist Notes Vol. 15, No. 4 N58 J.C. Godwin, D.A. Steen, D. Werneke, and J.W. Armbruster Table 1. Morphological data, sex, and reproductive state associated with 2 records of non-indigenous aquatic species observed in the Mobile Bay Watershed, AL, in 2014. Specimen 1 Specimen 2 Species Pterygoplicthys disjunctivus x pardalis Oreochromis niloticus Family Loricariidae Cichlidae Accession number AUM 63166 AUM 63560 Collection date 30 May 2014 11 July 2014 State AL AL County Mobile Baldwin Watershed Dog River Magnolia River Latitude 30.58735 30.39159 Longitude -88.12598 -87.79568 Collectors J.C. Godwin, A.M. Godwin, G.W. Godwin J.C. Godwin, D.A. Steen Identified by J.W. Armbruster D. Werneke Sex female female Standard length 233 mm 255 mm Wet mass (70% ETOH) 215.7 g 610.0 g Reproductive condition Eggs inside body cavity (likely released Eggs in mouth at time of from the ovaries after death as tissue capture and exhibited deteriorated) bright pink breeding coloration on throat and abdomen Figure 1. Lateral and ventral views of Pterygoplicthys disjunctivus x pardalis (AUM 63166) collected from Dog River, Mobile County, AL. in Mississippi. The significance of our 2014 record is that it confirms that this species is reproducing in Alabama. P. pardalis Castelnau (Amazon Sailfin Catfish) is native to much of the lowlands of the Amazon River Basin of South America, and P. disjunctivus Weber (Vermiculated Sailfin Catfish) replaces it in the Madeira River drainage of the Amazon Basin (Armbruster and N59 2016 Southeastern Naturalist Notes Vol. 15, No. 4 J.C. Godwin, D.A. Steen, D. Werneke, and J.W. Armbruster Page 2006, Weber 1992). Differences between the 2 species are subtle: lines on the posterior portion of head of P. pardalis vs. spots in P. disjunctivus, and most of the spots free on the abdomen with only some combining to form vermiculations in P. pardalis vs. all spots joined into a network of lines in P. disjunctivus (Fig. 1). Using these characters, our specimen is clearly the P. pardalis morphotype. Despite Weber’s (1992) revision, more work is needed to determine the range of variability of color in P. pardalis to determine if P. disjunctivus is distinct. Specimens identified as both species are widely established in peninsular Florida and locally established in other southeastern states (USGS 2016); however, it is likely that the introduction was actually a hybrid of the 2 species. Wu et al. (2011) found that Pterygoplichthys in Taiwan confidently identified as P. pardalis had P. disjunctivus mitochondrial DNA and vice versa, and that many specimens had intermediate morphologies. They found evidence for free gene-flow from the P. pardalis morphotype and the P. disjunctivus morphotype indicating that either P. disjunctivus was not valid, or aquarium specimens were the result of an early hybridization event. Based on extensive examination of specimens and photos of introduced specimens from around the world by J.W. Ambruster (unpubl. data) and previous revisionary work on the genus (Armbruster and Page 2006), we recognize that introduced specimens worldwide, as well as specimens from the aquarium trade, range in morphology from P. pardalis to P. disjunctivus and should, per Wu et al. (2011), be classified as hybrids. Suspected mechanisms of introduction are aquarium releases and escape from fish farms, but we know of no fish farms in southern Alabama that could be a source of the species. Impacts attributed to presence of Pterygoplichthys include increased siltation due to riverbank excavation by male fish and potential destabilization of banks and increased erosion. Pterygoplichthys species graze on algae, benthic organisms, and detritus, and they may potentially affect indigenous invertebrate communities (USGS 2016). Our specimen was an adult with ripe ovaries, suggesting that Pterygoplicthys may be reproducing in Alabama. Nile Tilapia are native to tropical and sub-tropical Africa and the Middle East and have been widely used in aquaculture, which is the primary route of introduction into North American waters. This species is established in Mississippi, Florida, and likely Georgia (USGS 2016). Our observation suggests that they are also established in Alabama. Nile Tilapia feed on aquatic macrophytes, prey on native fishes and amphibians, and compete with native fishes (US Geological Survey 2016). Although we were not looking for exotic fishes in southern Alabama, we found 2 species of potential environmental or economic concern. It is likely that studies conducted specifically to detect exotic aquatic species in Alabama would generate new and important information about the presence, distribution, and demography of these animals in the state. In particular, a combination of traditional and eDNA (environmental DNA) sampling in a systematic sampling framework might generate important insights (Lodge et al. 2012). Acknowledgments. This publication is Contribution No. 732 of the Auburn University Museum of Natural History, Auburn, AL. Funding was provided by the Alabama Department of Conservation and Natural Resources, Montgomery, AL. IACUC 2013-2357. Literature Cited Armbruster, J.W. 2004. Phylogenetic relationships of the suckermouth armoured catfishes (Loricariidae) with emphasis on the Hypostominae and the Ancistrinae. Zoological Journal of the Linnean Society 141:1–80. Armbruster, J.W., and L.M. Page. 2006. Redescription of Pterygoplichthys punctatus and description of one new species of Pterygoplichthys (Siluriformes: Loricariidae). Neotropical Ichthyology 4:401–409. 2016 Southeastern Naturalist Notes Vol. 15, No. 4 N60 J.C. Godwin, D.A. Steen, D. Werneke, and J.W. Armbruster Gurevitch, J., and D.K. Padilla. 2004. 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US Geological Survey (USGS). 2016. Nonindigenous Aquatic Species Database. Available online at Accessed 25 April 2016. Weber, C. 1992. Révision du genre Pterygoplichthys sensu lato (Pisces, Siluriformes, Loricariidae. Revue Francaise d’Aquariologie Herpétologie 19:1–36. Wilcove, D.S., D. Rothstein, J. Dubow, A. Philips, and E. Losos. 1998. Quantifying threats to imperiled species in the United States. BioScience 48:607–615. Wu, L.-W., C.-C. Liu, and S.-M. Lin. 2011. Identification of exotic sailfin catfish species (Pterygoplichthys, Loricariidae) in Taiwan based on morphology and mtDNA sequences. Zoological Studies 50:235–246.