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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 - jcg0001@auburn.edu.
Manuscript Editor: Nathan Franssen
Notes of the Southeastern Naturalist, Issue 15/4, 2016
2016 Southeastern Naturalist Notes Vol. 15, No. 4
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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
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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.
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N60
J.C. Godwin, D.A. Steen, D. Werneke, and J.W. Armbruster
Gurevitch, J., and D.K. Padilla. 2004. Are invasive species a major cause of extinctions? Trends in
Ecology and Evolution 19:470–474.
Holden, M.H., J.P. Nyrop, and S.P. Ellner. 2016. The economic benefit of time-varying surveillance
effort for invasive species management. Journal of Applied Ecology DOI:10.1111/1365-
2664.12617.
Lodge, D.M., C.R. Turner, C.L. Jerde, M.A. Barnes, L. Chadderton, S.P. Egan, J.L. Feder, A.R. Mahon,
and M.E. Pfrender. 2012. Conservation in a cup of water: Estimating biodiversity and population
abundance from environmental DNA. Molecular Ecology 21:2555–2558.
Nico, L.G., and P.L. Fuller. 1999. Spatial and temporal patterns of nonindigenous fish introductions
in the United States. Fisheries 24:16–27.
Pimentel, D., L. Lach, R. Zuniga, and D. Morrison. 2000. Environmental and economic costs of nonindigenous
species in the United States. BioScience 50:53–
65.
Ricciardi, A., and J.B. Rasmussen. 1999. Extinction rates of North American freshwater fauna. Conservation
Biology 13:1220–1222.
US Geological Survey (USGS). 2016. Nonindigenous Aquatic Species Database. Available online at
http://nas.er.usgs.gov/default.aspx. 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.