Exotic Fishes in Fresh and Brackish Waters of Florida*

Home , Cichla ocellaris, Kissing gourami, Snapper Creek

WALTER R. COURTENAY, JR, HARRY F. SAHLMAN, WOODARD W. MILEY, II

DAVID J. HERREMA Department of Biological Sciences, Florida Atlantic University, Boca Raton, Florida 33432, USA

ABSTRACT S. Ramsey, pers. comm.). Almost 50 per cent of this traffic entered through the ports of Miami and Tampa, At least 38 species and several hybrids of exotic fishes Florida. A large percentage of fishes entering the have been found in fresh and brackish waters of Florida. Twenty species and five hybrids are at present established United States through other ports of entry is trans- in the form of reproducing populations. The ornamental shipped to Florida. These imports constitute approxi- aquarium fish industry has been the major source of these mately 20 per cent of the fishes sold to home aquarists introductions. Several methods of introductions are con- (Boozer, 1973). sidered and recommendations presented toward preventing Holding, culture, and breeding of exotic fishes for repetitions in the future. Future dispersal of exotics by the ornamental aquarium fish trade is a major industry channelization projects should become part of environmental impact statements. in Florida, involving more than 250 fish farms (Axelrod, 1971), and supplying nearly 80 per cent of the US demand (Boozer, 1973). Ornamental aquarium fishes are 'accidentally' released from many of these farms into open waters through unprotected effluent INTRODUCTION pipes or are periodically dumped when tanks and ponds are drained. Reviews of this and other sources Any additive to an aquatic situation, whether of introduction are given by Courtenay & Robins chemical, physical, or biological, which alters water (1973) and later in this paper. quality or the quality and quantity of its ecosystems, The mild climate of southern Florida and the supply can be considered as a pollutant. Biological pollutants of well-water of nearly constant temperature are great in the form of introductions of non-indigenous or advantages to the ornamental aquarium fish industry. exofic (foreign) species of organisms may be equally as Lack of safeguards to prevent escape of fishes and a serious in impact to aquatic ecosystems as are chemical massive system of interconnecting waterways provide and physical additives (Lachner et al., 1970). Permiss- a continuing supply of exotic fishes with access to and ive habitats (those not fully occupied with regard the opportunity for establishment in open waters of to trophic levels and species niche concepts) and the state. weakened environments (those altered naturally or by The presence of exotic fishes in Florida waters was man), are particularly susceptible to establishment of first recorded by Burgess (1958). Crittenden (1962), non-indigenous or exotic species. In some cases, the Springer & Finucane (1963), Rivas (1965), Ware (1966), introduced forms may become dominant (Laycock, King (1968), Buntz &Manooch (1968, 1969 a,b), Buckow 1966; King, 1968; McDowall, 1968; Regier, 1968; (1969), Idyll (1969), Ogilvie (1969a, b) Buntz & Lachner et al., 1970; Courtenay & Ogilvie, 1971). Chapman (1970), Lachner et al. (1970), Courtenay & While the addition of chemical and physical pollutants Ogilvie (1971), and Courtenay & Robins (1973) have can be reduced or terminated at any time, a biological further documented introductions in Florida. pollutant, once established, typically cannot be Prior to 1970, no specific attempt had been made removed from the environment. to determine which species of exotic fishes were present During 1972, live fish imports into the United States in Florida waters except for a few local surveys. This totalled approximately 110 million individuals, mostly report represents the first comprehensive study of this destined for the ornamental aquarium fish trade (John subject and documents these introductions. Collec- * This study was supported by Florida Game and Fresh tions were made using minnow seines up to 24 ft Water Fish Commission Dingell-Johnson Project F-28, (7-2 m) in length, electrofishing devices, dip nets, and Florida. block nets, or with 5 per cent emulsified rotenone. 292 Biological Conservation, Vol. 6, No. 4, October 1974-0 Applied Science Publishers Ltd, England, 1974—Printed in Great Britain Courtenay, Sahlman, Miley & Herrema: Exotic Fishes in Fresh and Brackish Waters of Florida 293

EXOTIC FISHES IN FLORIDA POECILIDAE Belonesox belizanus Kner—Pike killifish (E) Poecilia latipunctata (Meek)—Broadspotted Thirty-eight species and several hybrids of exotic molly (E) Poecilia petenensis (Gunther)—Swordtail molly (E) fishes have been found in Florida waters (Table I). Poecilia reticulata Peters—Guppy (E) Most of them were taken in 62 collections made in Poecilia sphenops (Valenciennes)—Liberty molly central and southern Florida between 1 July 1970 and Poecilia hybrid (probably latipinna x velifera)—Black 31 July 1972. Twenty species and five hybrids are molly (E) known to be established as reproducing populations. Poecilia hybrid—Lyretail Black molly (E) Xiphophorus helleri Heckel—Green swordtail (E) Xiphophorus maculatus (Giinther)—Southern platyfish TABLE I (E) Xiphophorus variatus (Meek)—Variable platyfish (E) Introduced freshwater fishes collected in Florida, Xiphophorus variatus xiphidium (Gordon)—Shortblade 1968-72. ( E) following the common name denotes swordtail those species which are established as evidenced by Xiphophorus maculatus x helleri—Red swordtail (E) reproductive populations Xiphophorus maculatus x variatus—(several varieties) (E) ANABANTIDAE Xiphophorus helleri x variatus—(several varieties) (E) Anabas testudineus (Bloch)—Climbing perch (E)1 Betta splendens Regan—Siamese fightingfish 1 Not collected by us; reported by Herbert Axelrod, Ross Colisa lalia (Hamilton-Buchanan)—Dwarf gourami Socolof, and Elywn Segrest (pers. comm.). Ctenopoma nigropannosum (Reichenow)—Twospot 2 Not collected by us; collected by Ralph W. Yerger and climbing perch (E) William L. Wegener (pers. comm.). Helostoma temmincki Kuhl and Van Hasselt—Kissing 3 Not collected by us; reported by Vernon E. Ogilvie gourami (pers. comm.). Macropodus opercularis (Linnaeus)—Paradisefish 4 Not collected by us; collected by Ralph W. Yerger. Trichogaster leeri (Bleeker)—Pearl gourami Trichogaster trichopterus (Pallas)—Blue gourami Anabantidae Seven species of anabantids were collected, two of CHARACIDAE Colossoma nigripinnis (Cope)—Pacu 2 which, the twospot climbing perch (Ctenopoma Serrasalmus nattereri Kner—Caribe3 nigropannosum) and the climbing perch (Anabas Serrasalmus rhombeus (Linnaeus)—White piranha testudineus), appear to be established. Specimens of Siamese fightingfish (Betta splendens), dwarf gourami CICHLIDAE (Colisa lalia), kissing gourami (Helostoma temmincki), Aequidens pulcher (Gill)—Blue acaral paradisefish (Macropodus opercularis), blue gourami Astronotus ocellatus (Agassiz)—Oscar (E) (Trichogaster trichopterus), and pearl gourami (Tri- Cichlasoma bimaculatum (Linnaeus)—Black acara (E) chogaster leeri) were collected in Lake Worth Drainage Cichlasoma cyanoguttatum (Baird and Girard)—Rio Grande perch (E) District canal L-15, west of Atlantis and Lantana, Cichlasoma meeki (Brind)—Firemouth cichlid Palm Beach County. The dwarf gourami was also Cichlasoma octofasciatum Regan—Jack Dempsey (E) collected east of Ruskin, Hillsborough County. Ross Geophagus brasiliensis (Quoy and Gaimard)—Pearl B. Socolof and Herbert R. Axelrod (pers. comm.) have cichlid informed us that climbing perch, as well as twospot Hemichromis bimaculatus Gill—Jewelfish (E) Tilapia aurea (Steindachner)—Blue tilapia (E) climbing perch, have been established in northwestern Tilapia melanotheron (Riippell)--Blackchin tilapia (E) Manatee County for several years. We collected the Tilapia mossambica (Peters)—Mozambique tilapia (E) latter species there. Unlike climbing perch which are herbivorous, CLARIIDAE twospot climbing perch are carnivores feeding in their Clarias batrachus (Linnaeus)—Walking catfish (E) native habitat on small fishes and insect larvae (Sterba, 1962). Both fishes are relatively small (climb- CYPRINIDAE ing perch reach about 25 cm in length and twospot Barbus sp.—Tinfoil barb climbing perch about 17 cm) and both are somewhat Barbus conchonius Hamilton-Buchanan—Rosy barb 'shy', preferring areas of dense vegetation. Climbing Barbus gelius (Hamilton-Buchanan)—Golden barb perch have an extraordinary capability for wide and Brachidanio rerio (Hamilton-Buchanan)—Zebra danio Carassius auratus (Linnaeus)—Goldfish rapid dispersal by being able to traverse several Cyprinus carpio Linnaeus—Carp (E)4 hundred metres of land when humid conditions prevail (Sterba, 1962). Both species of these established

LORICARHDAE anabantids have a very limited distribution at present Hypostomus sp.—Armoured Catfish (E) and are represented by small and unstable populations. 294 Biological Conservation All anabantids collected were escapees from species of exotic fish known to be established in ornamental aquarium fish farms. Everglades National Park (reported as Aequidens portaIegrensis by Kushlan, 1972). In some major Characidae canals west of Fort Lauderdale, the black acara is the An unusual collection made in an abandoned dominant species, comprising up to 64 per cent of all swimming pool in South Miami resulted in the capture fishes present by weight (biomass). Cichlasoma of two specimens of the white piranha (Serrasalmus bimaculatum was found in 24 of 44 collections made in rhombeus). It was reported that four to six piranhas had been introduced the previous year and that the two remaining specimens had survived the fourth coldest winter recorded in Florida's history. A specimen of the caribe (Serrasalmus nattereri) was caught on hook and line by a Florida highway patrolman. It was reported to have been caught in a borrow pit connected to Snapper Creek Canal in Miami at State Road 826. A collection made with rotenone at this site failed to yield additional specimens. One specimen of the pacu (Colossoma nigripinnis) was collected in Leon County at Waverly Pond, Tallahassee, in October 1968 (Ralph W. Yerger, pers. comm.). Several specimens of CoIossoma, perhaps of the same species, were collected several years ago in a pond in Daytona Beach, Volusia County (Vernon E. Ogilvie and William L. Wegener, pers. comm.). Colossoma is not known to be established. All specimens were probably released from home aquaria.

Cichlidae At least eleven species of cichlids, eight of which are established, have been collected in Florida. Cichlosomo bimaculatum The blue acara (Aequidens pulcher) was common in waters adjacent to tropical fish farms in the Tampa Bay area several years ago (Ross B. Socolof, pers. comm.). We did not collect any specimens and assume that this species did not become established. The oscar (Astronotus ocellatus), deliberately released Fig. 1. Distribution of the black acara (Cichlasoma from an ornamental aquarium fish farm in south bimaculatum) in Florida. Major drainage canals are eastern Dade County, is established in Dade County indicated by wide lines. in the Miami Lakes Estates section, in the Little River area, and in the Snapper Creek—Black Creek canal south eastern Florida, and in 16 of these it represented system. Introduction occurred in the late 1950s. 5 per cent or more of the fish biomass. In four col- Subsequent new introductions to other sites were lections, this species comprised 30 per cent or greater made by fishermen. Oscars will take both natural and of the fish biomass. In one canal, near the suspected artificial baits and are frequently caught by anglers. original site of introduction in northern Broward Attempts to popularize this fish by local sports County, the black acara now comprises 80 per cent of columnists in the late 1950s failed. Its present status as the total fish biomass. a sport fish is unclear. The black acara is very territorial, reacting aggress- The black acara (Cichlasoma bimaculatum), an ively to any would-be intruders. Unlike native species, escapee from one or more ornamental aquarium fish it was observed spawning and defending nesting sites farms, has the widest distribution of all exotic fishes during all but the coldest months of the year. Typically in southeast Florida (Fig. 1). It is established from this species utilizes spawning sites similar to those of west of Lantana, Palm Beach County, southward centrarchids. In areas where spawning sites are through Broward and Dade Counties, and westward limited, this species was observed making use of into northeastern Monroe County. It is the only marginal areas such as small ledges in borrow pits. Courtenay, Sahlman, Miley & Herrema: Exotic Fishes in Fresh and Brackish Waters of Florida 295 High fecundity, parental care of young, a prolonged brasiliensis) was taken in a canal west of Lantana, spawning season, and adaptability toward utilizing Palm Beach County, near a fish farm. Additional spawning sites have enabled the black acara to collecting indicated that this species is not at present establish and maintain high population densities in established. canals in south eastern Florida. Rivas (1965) first The jewelfish (Hemichromis bimaculatus), another reported the black acara in Florida under the name escapee from the ornamental aquarium fish trade, has Aequidens portalegrensis, a misidentification which is been established in the Hialeah Canal—Miami River very common in the aquarium hobby literature. Canal system, Dade County, since before 1965 (Rivas, In 1964 a release of 10,000 juvenile tucanare or 1965). It is common in borrow canals along the western peacock bass, supposedly Cichla ocellaris, was made side of Miami International Airport. This species may in northern Dade County. This introduction was be established in Eureka Springs, Hillsborough sanctioned and conducted by the Florida Game and County. Fresh Water Fish Commission. South American Several species of Tilapia have been found in cichlids of the ocellaris type attain large sizes and are Florida waters. We are uncertain as to the proper reported to provide excellent fighting and food identification of two tilapia we collected. With the qualities (McClane, 1971). All introduced peacock exception of the blue tilapia (Tilapia aurea, identifica- bass were apparently killed during the cold winter of tion recently confirmed by Reeve M. Bailey and 1964-65. Interest in experimenting with this and William Smith-Vaniz), the specific names used herein other species of Cichla for possible future introduction should be considered tentative. continues in Florida (McClane, 1971; Courtenay & Blue tilapia have the most extensive distribution of Robins, 1973). all exotic fishes established in Florida (Fig. 2). Buntz & The Rio Grande perch (Cichlasoma cyanoguttatum), Manooch (1968) record the species from twelve while not considered a true exotic since it is native to counties: Hillsborough, Pinellas, Pasco, Polk, High- the Rio Grande drainage of Texas, is a non-indigenous lands, Hardee, DeSoto, Manatee, Sarasota, Charlotte, species utilized in the aquarium fish trade. It is now Glades, and Orange. The species was brought to established in an abandoned phosphate pit near Mulberry, Polk County. At this site, Rio Grande perch were numerous, although due to their relatively small size they constituted approximately 10 per cent of the total fish biomass. We observed this species to be utilizing almost all of the limited spawning sites normally used by centrarchids. The Rio Grande perch was previously reported from Six-Mile Creek, Hillsborough County, by Burgess (1958); we did not find any at that site in 1971. Buntz & Chapman (1970) record this species from Hillsborough County near the towns of Gibsonton, Riverview, and Ruskin. This report, however, appears to be based on a misidentification of juvenile Jack Dempseys (Cichlasoma octofasciatum). The firemouth cichlids (Cichlasoma meeki) were collected in a canal west of Lantana, Palm Beach County, adjacent to a fish farm from which they escaped. No evidence of reproduction was found at this site but this species is established in a limestone sinkhole on a private estate in South Miami, Dade Maple, eurec County. T me/one/hero" The Jack Dempsey (Cichlasoma octofasciatum) is messambica established west of Lantana, Palm Beach County, and in several roadside ditches in Hillsborough County. In both areas the presence and establishment of this species is restricted to the vicinity of tropical fish farms from which it has escaped. Spread to other areas is expected. A single specimen of the pearl cichlid (Geophagus Fig. 2. Distribution of three species of Tilapia in Florida, 296 Biological Conservation Florida from Auburn University in August 1961 and 2). Blackchin tilapia were observed grazing on green stocked in managed pits for aquatic plant control and blue-green algae in Lithia Springs where they experiments at the Pleasant Grove Research Station, constituted approximately 90 per cent of the total fish Hillsborough County, by the Florida Game and Fresh biomass. Aquatic vegetation of any kind was reduced Water Fish Commission (Buntz & Manooch, 1968). greatly, apparently due to grazing by this species. The News media touted the blue tilapia as an excellent food only conspicuous native fishes present, largemouth and game species, which inspired fishermen to move bass (Micropterus salmoides) and bluegills (Lepomis this fish to other areas. The blue tilapia is, in fact, not macrochirus), appeared diseased and undernourished. a game fish. Its food qualities are now being tested in Blackchin tilapia were found to be even more numerous the markets of south Florida, the Carolinas, and in the brackish waters of the Tampa Bay area. Its Georgia. habit of brooding eggs in the mouth cavity (mouth- Previous studies have shown that blue tilapia are brooding), parental care of young, and euryhaline capable of extremely rapid increases in percentage adaptability help to ensure the survival and dispersal biomass of the total fish in a given area, especially in of this tilapia. Although this species has some com- eutrophic lakes. In a 1966 fish survey made in Lake mercial value as a food fish (in 1968 it constituted Parker, in the City of Lakeland, Polk County, this 18,000 kg at 50c/0.45 kg of the commercial fishery in species was found to comprise 20 per cent by weight Tampa Bay (Buntz & Manooch, 1969a)), its detrimental of all fish (Buntz & Manooch, 1968); in 1969, in effects need to be considered before a valid and proper another population study, 2-8 per cent total biomass; assessment can be formulated. in 1970, 7.4 per cent (Forrest Ware, pers. comm ); The Mozambique tilapia (Tilapia mossambica) has and in 1972 they had increased to 69.1 per cent of the been collected in the Comfort Canal (the channelized total biomass (Vincent Williams, pers. comm.). south fork of the Miami River), Dade County (James Williams also sampled Lake Effie, near Lake Wales, Eggert, pers. comm.); Lake Worth Drainage District Polk County; per cent composition of total fish canal L-15, Palm Beach County (Ogilvie, 1969a); the biomass by blue tilapia was 0 per cent in 1966; 0.66 Civic Center Pond in Satellite Beach, Brevard County; per cent in 1968; and 93.26 per cent in 1972! Blue adjacent to a fish farm north of Vero Beach, Indian tilapia compete directly with native species for River County; in drainage ditches on a fish farm in spawning sites, food, and space (Buntz & Manooch, Micco, Brevard County, and in Six-Mile Creek, 1968). While it is doubtful that recently-allowed Hillsborough County (Fig. 2). Each of the sites where commercial exploitation will substantially reduce the Mozambique tilapia have been collected represents a populations of this species in Florida waters, there different source of introduction. At present, this species appears to be no alternative. is established in the south fork of the Miami River, in The Congo tilapia (Tilapia melanopleura) has been areas adjacent to a fish farm near the town of Fells- studied as a possible means of biological control for mere, Indian River County, and in Six-Mile Creek, aquatic plants in Florida. The Soil Conservation Hillsborough County. Service stocked the Bok Tower wildlife pond at Lake Near Fellsmere we collected fry, juvenile, and Wales, Polk County, with this species in 1964 (Buntz brooding adult Mozambique tilapia in a flooded area. & Manooch, 1969a). In 1969 the Florida Game and These fish were on beds under sable palms, at the Fresh Water Fish Commission conducted several bases of pine trees, and distributed throughout other experiments with this fish at Eustis, Lake County. areas where the substrate was free of vegetation. They This species was found to be highly aggressive and a had escaped from an adjacent fish farm where many threat to native aquatic plants which could result in specimens of the same species had been killed by management problems with both native fishes and rotenone by Florida Game and Fresh Water Fish waterfowl. Buntz & Manooch (1969a) reported Commission personnel just prior to our collection. 'nearly all vegetation, including water lilies, has been Within a matter of days following our collection, the annihilated on the pond, the only higher aquatic left reclaimed ditches were again populated by this species was a rush.' Experimentation was terminated and which had returned from the flooded area after heavy stocks destroyed in 1970. The Congo tilapia has not rains (Jonathan Davis, pers. comm.). been found in open waters of Florida to date. However, A reclamation of the Civic Center Pond at Satellite this species was found to be established in a closed Beach yielded only large adult specimens of Mozam- ditch on a fish farm near Micco, Brevard County. bique tilapia of approximately the same age. The The blackchin tilapia (Tilapia melanotheron), an source of introduction of this species at this locality escapee from one or more aquarium fish farms along is unknown, although it is believed that amateur Bullfrog Creek, Hillsborough County, is now estab- aquarists had released it into the pond. This tilapia lished throughout much of the Tampa Bay area (Fig. has subsequently returned to this site, apparently from Courtenay, Sahlman, Miley & Herrema: Exotic Fishes in Fresh and Brackish Waters of Florida 297 stocks in the Banana River, where it may be remain dormant until the first spring rains initiate established. activity. Periods of cold weather may be producing, High fecundity, parental care of young, and by natural selection, cold-resistant populations of this adaptiveness in utilizing spawning sites could enable species in southern Florida. Mozambique tilapia to establish and maintain large populations in southern Florida habitats. Robins (1969) has alluded to the adaptiveness of Tilapia mossambica by stating that this species is capable of breeding in 'fresh and brackish water up to 30 ppt salinity and that it survived to 40 ppt'. The relatively high salinity tolerances of this species enhance its potential for rapid and wide dispersal in south eastern Florida via the Intracoastal Waterway.

Clariidae The walking catfish (Clarias batrachus) apparently escaped from Penagra Aquariums, a large fish farm west of Deerfield Beach, Broward County, during the mid 1960s. This species is now established from the West Palm Beach Canal southward to the New River Canal, west of Fort Lauderdale, Broward County, a distance of approximately 36 miles (57.6 km). Vernon E. Ogilvie (pers. comm.) has informed us of their presence in Lake Okeechobee. Vincent Williams and Norman Young (pers. comm.) have recently confirmed earlier reports that walking catfish, probably released from one or more fish farms, are established in Clarias batrachus Hillsborough County. Ironically, one fish farmer in that county found it necessary to renovate his ponds after they were invaded by Clarias. The spread of Clarias (Fig. 3) has been both rapid ek ... and continuous. Its ability to withstand desiccation S and its habit of migrating during rainy periods have Fig. 3. Distribution of the walking catfish (Clarias in Florida. aided this fish in its dispersal. Walking catfish are batrachus) occasionally found in the Intracoastal Waterway Walking catfish are voracious, opportunistic feeders. where they live in salinities of 18 ppt (Courtenay, Stomach contents of 64 specimens yielded 35 per cent 1970), which further enhances their ability for north- insect carapaces (Haliplus sp., dytiscid beetles, south dispersal. mayflies, dragonflies, other beetles), 18 per cent fish Walking catfish do not appear to show a preference (Fundulus, Gambusia, and Lepomis were most com- for any particular water quality situation. They live mon), and 10 per cent plant material (Marianne C. well in clear, oxygen-rich water and in muddy swamp Porter, pers. comm.). This species has also been known water where there is virtually no dissolved oxygen. to go without food for as long as eight months in The presence in this species of aerial breathing devices aquaria without any ill effects except minor weight and blood which is buffered by urea permits existence losses (Courtenay, 1970). The most obvious detrimen- in anoxic waters. tal effects are seen during the 'dry' months when In 1968 and 1969 albino walking catfish were walking catfish aggregate in small ponds and either commonly seen and collected in northern Broward consume or kill most of the animals in these ponds and southern Palm Beach counties. The dark gray or within a few weeks (Courtenay, 1970). black form was more common and albinos were rare Walking catfish begin mass spawning migrations in in 1970-72. Whatever predation on this species late spring and early summer. Juveniles of about there may have been by other fishes or birds has 50 mm appear in the late summer and grow to probably been reduced by this reversion to the dark approximately 100 to 130 mm by winter. Late larval coloration. stages and early juveniles have been collected as late During cold, dry months walking catfish apparently in the year as the first week of November in Broward burrow into the sides of ponds and streams where they County. 298 Biological Conservation This species has also been released in Nevada Hillsborough County. These fishes were introduced (James E. Deacon, pers. comm.) and in southern from aquarium fish farms. This creek is soon to be California (Martin R. Brittan, pers. comm.), but joined to the Hillsborough River by the Tampa establishment other than in southern Florida is Bypass Canal Channelization Project of the US Army at present unknown. Corps of Engineers. Six-Mile Creek is a clear stream fed by nearly constant temperature springs and the Cyprinidae Hillsborough River is more turbid. Loricariids occupy Specimens of the rosy barb (Barbus conchonius), a wide variety of habitats in South America, and golden barb (Barbus gelius), tinfoil barb (Barbus sp.), unless temperature changes prove detrimental, range and zebra danio (Brachidanio rerio) were collected in expansion of these catfishes into the Hillsborough a canal west of Lantana, Palm Beach County. There River is quite likely. is no evidence of establishment of these cyprinids in Armoured catfishes have also been taken from the Florida. The source of introduction was an aquarium Snapper Creek drainage in Dade County since 1959. fish farm. Snapper Creek connects to the Tamiami Canal south- The grass carp (Ctenopharyngodon idella) is currently west of Miami International Airport. A 69 cm under investigation as a potential aquatic plant control specimen was collected by Henry Brown of Miami by several agencies in Florida. To date this species north of the Tamiami Canal along US route 27, in has been confined to experimental pools and ponds October 1971, just east of Water Conservation Area 3, and no evidence of accidental or deliberate release has Dade County, and only a few km north of Everglades been found. National Park. The source of these fishes in Dade It is not at present known whether grass carp will County appears to be from dumping of home aquaria. reproduce in Florida waters. If natural reproduction Hypostomus spp. are algae and detritus feeders. were possible, release of this fish could prove disastrous Stomach contents of specimens from Six-Mile Creek, to the aquatic resources of the state. This voracious Hillsborough County, consisted of unidentified green omnivore is preferentially herbivorous and has the algae and detritus. potential to denude large areas of vegetation, thus Rivas (1965) reported Hypostomus plecostomus as removing plant cover required for native aquatic established in a rockpit in west Miami. Florida Game organisms. Similarly, adverse effects on waterfowl and Fresh Water Fish Commission biologist Harold habitat are possible (Courtenay & Robins, 1972). Moody has informed us that a specimen of Hypostomus Grass carp are known to carry many parasites sp. was taken in Lake Jessup on the St John's River. (Stevenson, 1965; Szakolczai & Molnar, 1966; Armoured catfishes appear to be innocuous, occupying Bauer et al., 1969; Cross, 1969; Bardach et al., 1972). a niche which has minimum overlap with niches of Among these is the ciliate protozoan, Hemiophrys. native fish species. This exotic ciliate was recently reported in Missouri (John Crowder, pers. comm.). Although grass carp Poeciliidae were not noted in the same stream, they are present in Seven species and five hybrids of livebearing exotic the Mississippi River north of its juncture with the poeciliid fishes are established in Florida. Ohio River. The pike killifish (Belonesox belizanus) has been The carp (Cyprinus carpio) is known to have been established in southern Dade County since 1957. established for many years in drainages from Alabama Recently, we have had a report that it is established on and Georgia which enter the 'panhandle' region of the University of Miami Campus. It is also being sold Florida. to home aquarists. The goldfish (Carassius auratus) has been collected Other exotic poeciliids known to be established are in a canal near Homestead, Dade County, and one (localities by counties): the swordtail molly (Poecilia specimen was collected in Beecher Spring near Welaka, petenensis; Hillsborough and Palm Beach, separate Putnam County. This species is being reared by the introductions); broadspotted molly (Poecilia lati- US Fish and Wildlife Service to provide a food punctata; Palm Beach, a single introduction); guppy source for sport fishes being cultured in the federal (Poecilia reticulata; Hillsborough and Palm Beach, hatchery at Welaka. separate introductions); black molly (Poecilia, probably latipinna x velifera; Palm Beach, Brevard, Loricariidae Hillsborough and Polk, many introductions); lyretail At least two at present unidentified species of South black molly (Poecilia hybrid; Brevard, a single American armoured catfishes (Hypostomus) are introduction); southern platyfish (Xiphophorus macul- established in Florida. The largest concentration of atus; Hillsborough and Palm Beach, separate introduc- these fishes is in Six-Mile Creek, east of Tampa, tions); variable platyfish (Xiphophorus variatus; Palm Courtenay, Sahlman, Miley & Herrema: Exotic Fishes in Fresh and Brackish Waters of Florida 299 Beach, Brevard, Hillsborough, Manatee, many intro- become 'contaminated' with mixed species are often ductions); green swordtail (Xiphophorus helleri; pumped into nearby canals and streams; (3) heavy rains Brevard, Palm Beach, Polk, Hillsborough, and often flood fish farms,many of which are located on low Manatee, many introductions); red swordtail (Xipho- land, washing fishes into open waters; (4) fishes phorus maculatus x helleri; Palm Beach, Brevard resulting from an unusually successful breeding pro- and Hillsborough, many introductions); Xiphophorus gramme where supply far exceeds demand may be helleri x variatus (several varieties, Brevard and released; and (5) the release and establishment of both Hillsborough, several introductions); and Xiphophorus walking catfish in Hillsborough County and Mozam- maculatus x variatus (several varieties, Brevard, one bique tilapia elsewhere in Florida appear to have introduction). The only exotic poeciliids collected that resulted from the purposeful dumping of illegal stocks showed total lack of establishment were the liberty of these fishes. molly (Poecilia sphenops) and the shortblade sword- Those species of established ornamental aquarium tail (Xiphophorus variatus xiphidium). fishes which are no longer confined to drainages near Most of these exotic poeciliids were introduced by fish farms but which were released from this source escape or dumping from aquarium fish farms. Some include five cichlids: the oscar, the black acara, the were stocked in the Hillsborough County area for jewelfish, the blackchin tilapia, and the Mozambique mosquito control. Belonesox belizanus was released tilapia, and the walking catfish. Of these, the black after termination of a research project (Courtenay & acara at present has the widest distribution, occurring Robins, 1973). Amateur aquarists released two species throughout portions of four counties. Although this and several viable hybrids into the Satellite Beach species has been cultured in south Florida since the Civic Center Pond. 1930s (Ross B. Socolof, pers. comm.), they were not Of the seven species and five hybrids of exotic noted in fish collections prior to the mid-to-late 1950s. poeciliids established in Florida, only one species, the Black acara and walking catfish are the most rapidly pike killifish, appears to have significant ecological spreading exotic fishes in southeast Florida. There is effects on native biota. With the exception of this every indication that black acara may become the species, other exotic poeciliids established in Florida dominant freshwater fish in this area within a decade. waters have food and feeding habits that are almost All aquarium fishes that are established and re- identical to those of our native poeciliids. It is unlikely stricted to drainages near or on fish farms have the that food resources of poeciliids (plant material and potential for future dispersal. Moreover, any exotic small invertebrates) are limiting. The bright colours fish being cultured in outdoor ponds has the potential and conspicuous nature of the exotic poeciliids render for both establishment and dispersal. them easy prey for native fish-eating predators, which Exotic fishes that were deliberately released and are probably precludes their dispersal into more open established include blue tilapia and pike killifish, waters. and several small poeciliid species. The release and Pike killifish have survived temperatures as low as rapid dispersal of the blue tilapia resulted from their 10°C and salinities of 50 ppt (Belshe, 1961). The movement into various drainages by fishermen. The range of temperatures and salinities in south eastern pike killifish was introduced (50 specimens) in April or Florida would not act as barriers to the dispersal of May 1957 after a medical research project in which they Belonesox. were used was terminated. This species now occurs over approximately 160 square miles (400 km2) in southern Dade County. In some canals in that area, the pike DISCUSSION killifish now comprises 20 per cent of the total fish biomass, a remarkable achievement for a poeciliid ! Introductions and Dispersal Green swordtails and one hybrid, the red swordtail, Approximately 50 per cent of our collections were were released in the Tampa Bay area for mosquito made in the vicinity of ornamental aquarium fish control, which appears incongruous in view of the farms. Selective sampling was conducted to determine presence of native mosquitofish and sailfin mollies which species were being introduced from this (Poecilia latipinna) in this same area. We strongly source. Our results indicate that nearly every species suspect that fish farmers who raise large numbers of of exotic fish held or cultured in Florida can be swordtails in Hillsborough County stimulated political expected to find its way to open waters. and financial support for these releases. Exotic fishes are released into Florida waters from The home aquarist appears to play only a minor fish farms by five means: (1) unscreened effluent pipes role in contributing exotic fishes to open waters. The from holding and culture tanks and ponds typically Jelease of a few specimens seems an unlikely way to emptying into adjacent waterways; (2) ponds that establish fish (Courtenay & Robins, 1973) but the 300 Biological Conservation potential for establishing fish by this means is never- authority to issue or deny such permits upon comple- theless present. Establishment of one or more un- tion of ecological studies on the imported species, and identified species of armoured catfishes in the Snapper declares violation of this statute to be 'misdemeanor Creek drainage of Dade County in all likelihood of the first degree.' Rule 9.07 of the Game and Fresh resulted from one or more aquarium dumpings. The Water Fish Commission prohibits introduction or use specimens of the pacu found at Tallahassee and for bait or any purpose which might result in liberation Daytona Beach were doubtlessly released from home of any non-native fish or other aquatic organisms aquaria; there is no evidence to date, however, that without a permit from the Commission; this rule also these exotics became established. Mozambique tilapia includes a list of restricted fishes, provides for inspec- may be established in the Banana River as a result of a tion of hatcheries holding fish for introduction, release by aquarists into the Satellite Beach Civic prohibits the possession for sale or use of live or dead Center Pond. aquatic organisms and the disposal of such stocks Carp entered Florida via interstate drainages from which are infected or have been exposed to disease or Georgia and Alabama. The latter state released the parasites, and specifically prohibits the operation of grass carp into its waters in 1969 and this species may any facility where non-native fish are cultured or held eventually enter Florida by the same routes as did for sale or any other purpose if that facility lacks over- carp. It is likely that other stocks of grass carp are flow protective devices to prevent escape of eggs or already in Florida illegally. Courtenay & Robins young of such fish into state waters. (1973) have reviewed the grass carp situation in this With the large number of fish farms in Florida and state. an inadequate number of law enforcement personnel available within the Commission, these statutes and Industry, Laws, and Ecological Considerations the rule are at present largely unenforceable. Never- Few persons are aware of the major size and theless, the statutes and the rule are, in our opinion, importance of the ornamental aquarium fish industry adequate legislation to reduce or prevent future in Florida. Wholesale turnover of livestock alone introductions from fish farming operations. The grosses more than $30 million per year. Aquarium section of Rule 9.07 restricting certain fishes remains fishes and transport water comprise the largest open and is subject to continual review, additions, or percentage by weight of airfreight into and out of even deletions. Tampa—St Petersburg and the second largest at Miami. We would, however, strongly endorse legislation Industry provides a livelihood for thousands of requiring a warning to be printed in easily readable people in and out of Florida. type on all fish bags used in Florida retail and whole- Axelrod (1971) estimates that there are 20 million sale aquarium fish sales which would state that it is a aquaria in US homes, 6,000 pet shops and 10,000 misdemeanor to release any non-native fish into variety stores selling aquarium fishes and supplies, and Florida's waters. We would also support a statute that over 450 manufacturers and importers of aquarium all such dealers prominently display a sign in their supplies. He states that the three largest suppliers business establishments bearing the same warning. alone have annual retail sales of about $350 million. Besides the additional expense incurred by the Clearly the majority of exotic fishes now present in Commission in the hiring and training of personnel to Florida waters came from the ornamental aquarium enforce these regulations, similar effects may occur in fish industry. The reaction of some segments of the expenses of fishery management. Current game and government and some conservation organizations has fish regulations are the result of complex and costly been to ban the importation of exotic fishes. This is not research and are designed to ensure the protection the answer to the problem, and we are opposed to such and stability of populations of important native species legislation. Nothing can be done to eliminate the based on an environment without exotics. Such already established exotics that have more than a very introduced species could render present management localized distribution. But future introductions can be practices ineffective and would require the necessity sharply reduced or eliminated by a few precautionary for much new research and changes in management measures. techniques. Florida Statute 372.26 requires all fish importers to The ornamental aquarium fish industry has become possess an importation permit and prohibits all persons aware of the problems resulting from trade practices. from introducing any imported fish (which includes The Florida Tropical Fish Farms Association, Inc. both exotic and non-indigenous fishes) into the fresh has indicated its willingness to work toward preventing waters of the state. Statute 372.265 requires a permit future releases of its stocks. By diverting all effluent to sell or use non-indigenous animals, provides the waters from fish rearing and culturing facilities Game and Fresh Water Fish Commission with through an underground or above-ground dry well, Courtenay, Sahlman, Miley & Herrema: Exotic Fishes in Fresh and Brackish Waters of Florida 301 introductions from this source could be effectively BucKow, E. (1969). Exotics: new threat to US waters. stopped. All that is needed is an adequate sand and Field & Stream, May, pp. 16, 18, 20, 22, 24, 28. gravel filter which will allow passage of water but not BUNTZ, Jon & CHAPMAN, Phil (1970). A preliminary report livestock. Outdoor fish ponds located on floodable on the increasing establishment of non-native fish in the land should be diked. While this might not prevent Tampa Bay area. Unpublished report for the Florida passage of pathogens or parasites into open water- Game & Fresh Water Fish Commission, 6 pp.2 ways, fish farming would become an almost pollution- Bumrz, Jon & MANOOCH, free industry. Charles S., III (1968). Tilapia aurea Steindachner, a rapidly spreading exotic in Rapid and wide dispersal of exotic fishes in Florida south central Florida. Proc. a. Conf. SEast Game has been made possible by the massive gridwork of Fish Commn, 22, pp. 495-501. interconnected waterways (Courtenay & Robins, 1973). This fact is to be considered when new channel- BUNTZ, Jon & MANOOCH, Charles S., III (1969a). A brief summary of the cichlids in the south Florida region. ization projects are contemplated. Unpublished report for the Florida Game & Fresh Water Fish Commission, 3 pp.2

ACKNOWLEDGMENTS BUNTZ, Jon & MANNOCH, Charles S., III (19696). Fisherman utilization of Tilapia aurea (Steindachner) We express thanks to F. G. Banks, Bruce B. in Lake Parker, Lakeland, Florida. Proc. a. Conf. SEast Game Fish Commn, 23, pp. 312-19. Collette, Carter R. Gilbert, Kenneth Relyea, C. Richard Robins, Franklin N. Snelson, Jr., Forrest J. BURGESS, J. Edward (1958). The fishes of Six-Mile Creek, Ware, Kenneth D. Woodburn, John W. Woods, and Hillsborough County, Florida, with particular refer- Ralph W. Yerger for providing helpful comments on ence to the presence of exotic species. Proc. a. Conf. this manuscript and for advice and assistance in its SEast Game Fish Commn, 12, 8 pp. preparation. We also thank the following for informa- COURTENAY, Walter R., Jr. (1970). Florida's walking tion and cooperation: James W. Eggert, Dade County catfish. Ward's nat. Sci. Bull., 10, 69, pp. 1, 6, 4 Pollution Control; Herb Davis, Robert Graves, photos. Elwyn Segrest, Ross B. Socolof, Richard A. Stiegel, and Arthur H. Wilden, Florida Tropical Fish Farms COURTENAY, Walter R., Jr. & OGILVIE Vernon E. Association; Dennis Auth, Jon Buntz, Phil Chapman, (1971). Species pollution. Anim. Kingd., 74(2), pp. 22-8. David Cox, Jonathan Davis, Roger A. Martz, Harold Moody, Vernon E. Ogilvie, Forrest J. Ware, William COURTENAY, Walter R., Jr. & ROBINS, C. Richard (1972). L. Wegener, Vincent Williams, and Norman Young, The grass carp enigma. BioScience, 24, p. 210. Game and Fresh Water Fish Commission; Herbert R. Axelrod, T.F.H. Publications; and John Crowder, COURTENAY, Walter R., Jr. & ROBINS, C. Richard (1973). US Fish and Wildlife Service. Exotic aquatic organisms in Florida with emphasis on fishes: a review and recommendations. Trans. Am. Fish. Soc., 102, pp. 1-12.

References CRITTENDEN, Edward (1962). Status of Tilapia nilotica Linnaeus in Florida. Proc. a. Conf, SEast Game AXELROD, Herbert R. (1971). The Aquarium Fish Industry Fish Commn, 17, pp. 257-62. —1971. T.F.H. Publications, Jersey City, N.J., 7 pp. CROSS, D. G. (1969). Aquatic weed control using grass BARDACH, John E., RYTHER, John H. & MCLARNEY, carp. J. Fish Biol., 1, pp. 27-30. William 0. (1972). Aquaculture; the Farming and Husbandry of Freshwater and Marine Organisms. IDYLL, Clarence P. (1969). New Florida resident, the Wiley-Interscience, New York, 868 pp. walking catfish. Natn. geogr. Mag., 135, pp. 846-51. BAUER, 0. N., MUSSELIUS, V. A. & STRELKOV, J. A. (1969). Die Parasiten und Krankheiten von Ctenopharyngodon KING, Wayne (1968). As a consequence many will die. idella, Hypophthalmichthys molitrix und Aristichthys Fla Nat., 41(3), pp. 99-103, 120. nobilis Bei der Aufzucht in Teichwirtschaften der UdSSR. Z. Fisch. N.F., 17, pp. 205-13. KUSHLAN, JAMES A. (1972). The exotic fish (Aequidens portalegrensis) in the Big Cypress Swamp. Fla Nat., BELSHE, (1961). John F. Observations of an introduced 45(1), p. 29. tropical fish (Belonesox belizanus) in southern Florida. M.S. Thesis, University of Miami, Coral Gables, 1 LACHNER, Ernest A., ROBINS, C. Richard & COURTENAY, 71 pp. Walter R., Jr. (1970). Exotic fishes and other aquatic BOOZER, David (1973). Tropical fish farming. Am. Fish organisms introduced into North America. Smithson. Farm., 4(8) pp. 4, 5. Contr. Zoo/., 59, pp. 1-29. 302 Biological Conservation

LAYCOCK, George (1966). The Alien Animals. Natural SPRINGER, Victor G. & FINUCANE, John H. (1963). The History Press, Garden City, N.Y., 240 pp. African cichlid Tilapia heudeloti Dumeril, in the commercial fish catch of Florida. Trans. Am. Fish. Soc., MCCLANE, A. J. (1971). Pavon paradise. Field & Stream, 92, pp. 317-18. 75(10), pp. 49-51, 88, 90. McDowALL, R. M. (1968). Interactions of the native and STERBA, Gunther (1962). Freshwater Fishes of the World. alien faunas of New Zealand and the problem of Pet Library, Ltd, New York, 877 pp. fish introductions. Trans. Am. Fish. Soc., 97, pp. 1-11. STEVENSON, J. H. (1965). Observations on grass carp in OGILVIE, Vernon E. (1969a). Illustrated checklist of fishes Arkansas. Progve Fish Cult., 27, pp. 203-6. collected from the L-15 canal (Lake Worth Drainage District) in Palm Beach County, Florida. Unpublished SZAKOLCZM, J. & MOLNAR, K. (1966). Veterinary-medical report for the Florida Game & Fresh Water Fish investigations on the plant-eating fish species acclima- Commission, 10 pp. 2 tized in Hungary. Z. Fisch., 14, pp. 139-50.

OGILVIE, Vernon E. (1969b). Illustrated Guide to the Fresh WARE, Forrest J. (1966). Lake Morton Eradication Water Fishes of Florida, I. V & M Publishing Co., Project. Unpublished report for the Florida Game & West Palm Beach, Fla, 37 pp. Fresh Water Fish Commission, 2 pp.2

REGIER, Henry A. (1968). The potential misuse of exotic fishes as introductions. In: A symposium on introductions of exotic species. Dept. of Lands & Forests, Res. Rep., 82, pp. 92-111. 1 Available from Library, University of Miami, Coral RIVAS, Luis R. (1965). Florida freshwater fishes and conservation. Q. Jl Fla Acad. Sc., 28, pp. 255-8. Gables, Fl 33124, USA. 2 Available from Florida Game & Fresh Water Fish ROBINS, C. Richard (1969). Statement submitted to the Commission, 620 [S. Meridian Street, Tallahassee, Fl Invitational Conference on the use of exotic fishes and 32304, USA. related problems. Unpublished paper presented at 3 Available from Dr C. Richard Robins, University of Invitational Conference on Exotic Fishes, Washington, Miami, 10 Rickenbacker Causeway, Miami, Fl 33149, D.C., 4 pp. 3 USA.