Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide


Belonesox belizanus
(pike killifish)



Belonesox belizanus (pike killifish)


  • Last modified
  • 27 September 2018
  • Datasheet Type(s)
  • Invasive Species
  • Preferred Scientific Name
  • Belonesox belizanus
  • Preferred Common Name
  • pike killifish
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Metazoa
  •     Phylum: Chordata
  •       Subphylum: Vertebrata
  •         Class: Actinopterygii
  • Summary of Invasiveness
  • The pike killifish Belonesox belizanus is an ornamental fish, native to Central America, that occurs as an introduced species in southern Florida, USA. The species has been successfully introduced to aquatic...

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Belonesox belizanus (pike killifish); adult. A slender, elongate, fish with elongate jaws forming a prominent, pointed beak. Scales very small and numerous. Max. length15-20cm, often around 9.6 cm.
CaptionBelonesox belizanus (pike killifish); adult. A slender, elongate, fish with elongate jaws forming a prominent, pointed beak. Scales very small and numerous. Max. length15-20cm, often around 9.6 cm.
CopyrightPublic Domain - Released by the U.S. Geological Survey
Belonesox belizanus (pike killifish); adult. A slender, elongate, fish with elongate jaws forming a prominent, pointed beak. Scales very small and numerous. Max. length15-20cm, often around 9.6 cm.
AdultBelonesox belizanus (pike killifish); adult. A slender, elongate, fish with elongate jaws forming a prominent, pointed beak. Scales very small and numerous. Max. length15-20cm, often around 9.6 cm.Public Domain - Released by the U.S. Geological Survey


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Preferred Scientific Name

  • Belonesox belizanus

Preferred Common Name

  • pike killifish

Other Scientific Names

  • Belonesox belizanus belizanus Hubbs 1936
  • Belonesox belizanus maxillosus Hubbs 1936

International Common Names

  • English: pike killifish; top minnow

Local Common Names

  • Belize: pike killifish
  • Costa Rica: pepesca gaspar; pike killifish
  • Denmark: geddetandkarpe; gul geddetandkarpe
  • Finland: alligaattorikala
  • Germany: elber Hechtkärpfling; Hechtkärpfling; Lebendgebärender Hechtkärpfling
  • Guatemala: picudito
  • Mexico: picudito; pike killifish
  • Poland: szczupaczek zyworodny
  • Russian Federation: zhivorodyaschaya schuchka
  • Sweden: gäddtandkarp
  • USA: pike killifish

Summary of Invasiveness

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The pike killifish Belonesox belizanus is an ornamental fish, native to Central America, that occurs as an introduced species in southern Florida, USA. The species has been successfully introduced to aquatic and estuarine habitats because of its wide environmental tolerances, ability to colonise anthropogenically disturbed habitats, fast growth rates and ability to give birth to live offspring. B. belizanus is euryhaline and tolerant of salinities from freshwater to higher than that of seawater. Negative environmental impacts of introduced populations of B. belizanus include the predation of native fishes, with research conducted in Florida concluding that indigenous poeciliid and cyprinodontoid fishes were less abundant in water bodies invaded by B. belizanus in comparison with uninvaded water bodies. B. belizanus also competes for food resources with native piscivores such as Micropterus salmoides (largemouth bass) and Lepomis gulosus (warmouth) in the USA.

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Metazoa
  •         Phylum: Chordata
  •             Subphylum: Vertebrata
  •                 Class: Actinopterygii
  •                     Order: Cyprinodontiformes
  •                         Family: Poeciliidae
  •                             Genus: Belonesox
  •                                 Species: Belonesox belizanus

Notes on Taxonomy and Nomenclature

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Rudolf Kner described Belonesox belizanus in 1860. He also erected the new genus, Belonesox, of which B. belizanus was the sole species.

In 1936, Carl Hubbs recognized two subspecies of B. belizanus: Belonesox belizanus belizanus and Belonesox belizanus maxillosus (Robins, 2014). Belonesox belizanus maxillosus was described from the town of Progreso in the Yucatan Peninsula in Mexico. Hubbs (1936) described B. belizanus maxillosus as distinct from all other Middle American populations of Belonesox due to its more ‘robust’ morphology and ‘very large, broad, and heavy jaws’.

Recent genetic studies have determined that B. belizanus maxillosus is not distinct from other northern populations of Belonesox (Marchio and Piller, 2013). Marchio and Piller (2013) did not recommend the official synonymization of B. belizanus maxillosus until a formal morphological study, including the examination of gonopodia, is conducted. However, the synonymization of B. belizanus maxillosus has been acknowledged by the taxonomic database FishBase (Froese and Pauly, 2014). 


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References used for this section include Breder and Rosen (1966), Hensley and Courtenay (1980), Turner and Snelson (1984), Page and Burr (1991), Miller et al. (2005) and Robins (2014).

B. belizanus is the largest member of the Poeciliidae. As with many species in this family, maximum sizes are sexually dimorphic: females grow to 150 mm total length (TL) and males to 110 mm TL (Page and Burr, 1991). Hensley and Courtenay (1980) suggested the species may grow as large as 200 mm standard length (SL). Turner and Snelson (1984) found the mean sizes of fish from a nonindigenous population in Florida to be 103 mm SL (females) and 72 mm SL (males).

The body of B. belizanus is slender and elongated with large, conspicuous jaws forming a prominent pointed beak bearing long, cardiform teeth. B. belizanus is an obligate piscivore, and has evolved highly elongate jaws capable of a large gape (Ferry-Graham et al., 2010). The dorsal fin origin is well behind anal fin origin and males possess a prominent gonopodium. There are usually 52-63 lateral scales and 8-9 dorsal fin rays (Page and Burr, 1991).

B. belizanus is dark olive/grey dorsally and fades to white on the ventral surface. There are several longitudinal rows of small black spots on the lateral upper half of the body. A larger black spot on the mid caudal peduncle may be present. Young fish have a dark lateral stripe that is thought to aid their ability to mimic small floating twigs and plant matter at the water surface. 


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The native range of B. belizanus extends from the Atlantic slope drainages of the Río de La Antigua system in Veracruz, Mexico, east through the Yucatan peninsula, Belize, Guatemala and Honduras, and south into Nicaragua and northern Costa Rica (Rosen and Bailey, 1963; Greenfield and Thomerson, 1997; Bussing, 1998; Reis et al., 2003; Miller et al., 2005; Smith and Bermingham, 2005; Marchio and Piller, 2013; Robins, 2014).

The native range of B. belizanus spans three Central American ichthyological provinces: the Usumacincta (Mexico, Belize and Guatemala), Honduran, and San Juan (Nicaragua and Costa Rica) (Miller, 1966; Bussing, 1976; Hrbek et al., 2007).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

North America

MexicoWidespreadNative Not invasive Miller et al., 2005Occurs from the Río de La Antigua system in Veracruz, Mexico east through the Yucatan peninsula and into Belize and Guatemala
USAPresentPresent based on regional distribution.
-FloridaLocalisedIntroduced1957 Invasive Belshe, 1961; Courtenay et al., 1974; Miley, 1978; Turner and Snelson, 1984; Loftus and Kushlan, 1987; Loftus et al., 2004; USGS, 2015Initially reported in southeastern Dade County in 1957; established in Dade, Monroe, and Collier counties, including parts of Everglades National Park and Big Cypress National Preserve
-TexasAbsent, formerly presentIntroduced Not invasive Barron, 1964; Hubbs et al., 1978; Howells, 1992Reported from San Antonio River, San Antonio in the early 1960s though no longer exists

Central America and Caribbean

BelizeWidespreadNative Not invasive Greenfield and Thomerson, 1997
Costa RicaWidespreadNative Not invasive Bussing, 1998
GuatemalaWidespreadNative Not invasive Bestelmeyer and Alonso, 2000; Miller et al., 2005Common in lagoons, oxbow lagoons, smaller tributaries and seasonal and permanent rivers in the Laguna del Tigre National Park, Guatemala.
HondurasWidespreadNative Not invasive Miller et al., 2005
NicaraguaWidespreadNative Not invasive Miller et al., 2005

History of Introduction and Spread

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B. belizanus was first documented in Florida in canals in southeastern Dade County in 1957 (Belshe, 1961). This population resulted from the deliberate release of specimens used for medical research (Belshe, 1961; Robins, 2014).

B. belizanus persisted as a small population in several canals east of the Everglades for more than 20 years before expanding dramatically in the 1980s and 1990s (Courtenay, 1997; Trexler et al., 2000). It is now established or has been recorded in canals, ditches, mangrove swamps, rivers and other habitats in Dade, Hillsborough, Monroe and Collier counties, including parts of Everglades National Park, Big Cypress National Preserve and the Florida Panther National Wildlife Refuge (Belshe, 1961; Courtenay et al., 1974; Miley, 1978; Turner and Snelson, 1984; Loftus and Kushlan, 1987; Loftus et al., 2004; USGS NAS, 2015).

B. belizanus was recorded in 1984 in a borrow pit on North Key Largo, Monroe County, Florida, though the population is thought not to have become established (Courtenay and Meffe, 1989). It was found in the San Antonio River, Texas, in the early 1960s (Barron, 1964) and is also thought not to have become established there (Hubbs et al., 1978; Howells, 1992).


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Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
USA Mexico 1957 Intentional release (pathway cause) Yes Belshe (1961); Courtenay et al. (1974); Loftus and Kushlan (1987); Loftus et al. (2004); Marchio and Piller (2013); Miley (1978); Turner and Snelson (1984); USGS (2015); USGS NAS (2015); Welcomme (1988) Initially reported in southeastern Dade County, Florida, in 1957. A population discovered in Texas in the 1960s apparently no longer exists

Risk of Introduction

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There are three main factors likely to influence the risk of introduction of B. belizanus to natural environments: the popularity of the species as an ornamental fish; the size and/or nature of the species as an ornamental fish, and the number of naturalized introduced populations.

Some of the recorded nonindigenous populations of B. belizanus are the result of the release of unwanted ornamental fishes (USGS NAS, 2015). B. belizanus is a moderately popular ornamental fish species. Robins (2014) described B. belizanus as ‘of some value to aquarists,’ though its popularity is limited by its piscivorous nature and cannibalistic tendencies. Furthermore, Butler (2014) stated that this species becomes more aggressive towards other aquarium inhabitants with age. Thus, the popularity and therefore commercial demand for B. belizanus is limited.

In Australia, B. belizanus is not present in the ornamental fish industry and the species is illegal to import; therefore, the risk of introduction to aquatic habitats in Australia is negligible.

There is the potential for the natural dispersal and anthropogenic translocation of introduced populations of B. belizanus. This is more likely to occur in areas that contain multiple populations and/or larger and widely distributed populations (such as Florida, USA). In areas with larger and/or widely dispersed populations, there is also a greater risk of the general public collecting, translocating and potentially re-releasing fishes.

In Florida, the northward expansion of B. belizanus from southern Florida is limited by lower cold temperature tolerance of the species (lower limit approximately 10°C) (Hensley and Courtenay, 1980; Shafland and Pestrak, 1982); however, the local densities and spread of B. belizanus are likely to be influenced by a variety of physiochemical variables (including water temperature) and predation (Kerfoot et al., 2011). Shafland and Pestrak (1982) compared the lower lethal temperature of B. belizanus (approximately 10°C) with mean isotherms of winter stream temperatures in Florida and concluded that the species should have the thermal tolerance to expand its northerly range from south Florida to Gainesville, Florida (approximately 550 km north of the southern Florida population). However, Kerfoot (2012) considered that a more realistic gauge of northward movement of B. belizanus is the minimum temperatures at which the species will feed. By comparing the temperature at which the species ceased to feed with mean January minimum temperatures in Florida, it was concluded that B. belizanus would remain localized to south Florida, as it is now (Kerfoot, 2012).


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B. belizanus occurs in the surface waters of slow-flowing freshwater and brackish rivers, ponds, canals and lakes, and particularly habitats with abundant aquatic vegetation (Page and Burr, 1991; Froese and Pauly, 2014; Robins, 2014).

B. belizanus is euryhaline and populations may occur and reproduce at salinities ranging from zero to at least 35 ppt (Turner and Snelson, 1984). As such the species will thrive in brackish habits such as lagoons, mangroves and estuaries as well as nearshore marine habitats with salinities as high as 40 ppt (Froese and Pauly, 2014; Robins, 2014).

It is also noted to occur in hypoxic environments, such as anthropogenically-modified canals overgrown with aquatic and/or emergent vegetation (Froese and Pauly, 2014; Robins, 2014). For example, Connaly (1968) reported that B. belizanus has been found in aquatic habitats completely covered with algae.

In the Yucatan Peninsula along the Gulf of Mexico coast, B. belizanus often only occurs in lagoons and cenotes (sinkholes) due to the lack of surface water and alternative aquatic habitats (Marchio and Piller, 2013; Vega-Cendejas et al., 2013).

In the Pantanos de Centla wetlands on the coastal plain of the southern Gulf of Mexico, Macossay-Cortez et al. (2011) only found B. belizanus in marginal vegetation habitats.

Habitat List

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  Principal habitat Harmful (pest or invasive)
  Principal habitat Natural
Irrigation channels Principal habitat Harmful (pest or invasive)
Irrigation channels Principal habitat Natural
Lakes Principal habitat Harmful (pest or invasive)
Lakes Principal habitat Natural
Reservoirs Principal habitat Harmful (pest or invasive)
Reservoirs Principal habitat Natural
Ponds Principal habitat Harmful (pest or invasive)
Ponds Principal habitat Natural
Estuaries Principal habitat Harmful (pest or invasive)
Estuaries Principal habitat Natural
Lagoons Principal habitat Harmful (pest or invasive)
Lagoons Principal habitat Natural
Inshore marine Principal habitat Harmful (pest or invasive)
Inshore marine Principal habitat Natural

Biology and Ecology

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The diploid/haploid chromosome numbers of B. belizanus are 48-48/24 (Froese and Pauly, 2014).

Reproductive biology

The reproductive biology and ecology of B. belizanus was researched by Turner and Snelson (1984), who investigated introduced populations of the species in Dade County, Florida. The mean length of females was approximately 103 mm and most females larger than 75 mm SL were mature (i.e. contained yolked ova, fertilized eggs, or embryos). The mean length of males was approximately 72 mm SL and most males larger than 55 mm SL were mature. The adult sex ratio was significantly skewed in favour of females, though it did not differ significantly from parity among immature fish.

Farr (1989) stated that the species exhibits little or no courtship behaviour; conversely, Horth (2004) documented extensive courtship behaviour. Male B. belizanus repeat courtship behaviour in the presence of females. A male will position himself in front of, and perpendicular to, a female, and fan his fins and gonopodium (modified anal fin) while his colouration becomes more vibrant. This display is often followed by mating attempts (Horth, 2004).

B. belizanus is ovoviviparous and fertilization is internal. Males inseminate females with a gonopodium. Females may store sperm and produce subsequent broods independently of male fish. Turner and Snelson (1984) found that the average brood size was approximately 99 embryos, and superfetation (simultaneous broods of embryos at different developmental stages) was absent. Mean interbrood interval of females was 42 days in the laboratory (Turner and Snelson, 1984). In naturalized populations in Dade County, reproduction occurred all year. B. belizanus is an obligate piscivore from birth, and Turner and Snelson (1984) noted that laboratory-born neonates were immediately piscivorous and exhibited predator-avoidance behaviour. Although the jaws of juevniles are proportionally shorter than that of adults, the dentition of neonates resembles that of adults in relative size, shape and arrangement of teeth (Greven and Brenner, 2008).

Robins (2014) stated that brood size may be as large as 322 and that B. belizanus neonates are approximately 15 or 16 mm at birth. B. belizanus is fast growing and may become reproductively mature within 6 to 12 months (Robins, 2014).

Physiology and phenology

Harms and Turingan (2012) observed that, although B. belizanus is an obligate piscivore, it consumed shrimp in addition to fish in a laboratory environment. These researchers suggested that that this dietary flexibility has contributed to invasion success of B. belizanus in southern Florida.

Turner and Snelson (1984) noted that B. belizanus neonates immediately exhibited complex survival strategies including predator-avoidance behaviours.


B. belizanus is ‘relatively short-lived’ (Robins, 2014). Other poeciliids, such as Gambusia sp., live a maximum of 1 to 2 years and it is likely that B. belizanus would live for a similar period.

Activity patterns

Greven and Brenner (2008) reported that B. belizanus stalks fish with minimal body movement, followed by an explosive lunge to grasp the prey.

Neonates/juveniles remain motionless at the water surface, mimicking floating foliage and twigs to avoid predation (Robins, 2014). In an aquarium environment, it was found that neonates remained motionless at the water surface when parents and adult B. belizanus were present, and became active and fed when parents/adult B. belizanus were removed. This innate behaviour may reduce parental cannibalism (Breder and Rosen, 1966).

Population size and density

Kerfoot et al. (2011) detailed five datasets of B. belizanus collections from research conducted in southern Florida. Although B. belizanus occurs in many different habitats there, the species has remained at relatively low, but variable densities (Trexler et al., 2000). For example, one dataset of 10 annual collections (1m2 throw traps) yielded only 11 specimens in total.

Kerfoot (2012) suggested that juvenile B. belizanus exhibit greater environmental tolerances and may therefore be equipped with the physiological flexibility to exercise greater habitat choice than adult fish. This physiological flexibility may allow juveniles to disperse to a greater range of habitats than adult fish and thus reduce potential intraspecific competition with adults for limited food resources.


B. belizanus is piscivorous (Hensley and Courtenay, 1980; Turner and Snelson, 1984; Robins, 2014).

Dietary analysis of field-caught B. belizanus in Dade County, Florida, indicated that surface-dwelling poeciliids including Gambusia sp., Poecilia sp. and B. belizanus were the most common food items in introduced populations (Turner and Snelson 1984). Hinojosa-Garro et al. (2013) investigated the diet of native populations in the Yucatan Peninsula, Mexico and also recorded a strictly piscivorous diet.

B. belizanus of all life stages and sizes are cannibalistic (Belshe, 1961; Miley, 1978; Turner and Snelson, 1984; Robins, 2014). B. belizanus may consume fishes of up to half their own body length, though a preference is shown for shall-bodies fishes. The capture and swallowing of fishes is facilitated by the moveable elongate jaws and large unicuspid teeth of B. belizanus (Greven and Brenner, 2008)

Neonates are able to feed on new-born guppies (Poecilia sp.) and platyfishes (Xiphophorus sp.) almost immediately after birth (Breder and Rosen, 1966). Juveniles prey on other juvenile or larval fishes (Robins, 2014).

In an aquarium environment B. belizanus generally only consumes live fishes, though some captive individuals may accept earthworms, insects, tadpoles, beef heart and sometimes pellets (Butler, 2014).


As an introduced species in Dade County, Florida, B. belizanus predominantly feeds upon, and lives in close association with, surface-dwelling poeciliids including Gambusia sp. and Poecilia sp. (Turner and Snelson, 1984).

Environmental requirements

B. belizanus is euryhaline and populations may occur and reproduce at salinities ranging from zero to at least 35 ppt (Turner and Snelson, 1984). As such, the species thrives in brackish habits including lagoons, mangroves and estuaries, as well as nearshore marine habitats with salinities as high as 40 ppt (Froese and Pauly, 2014; Robins, 2014). B. belizanus will live indefinitely in sea water and survives salinities of 40-50 ppt for limited periods (Belshe, 1961). It is suggested that the species be kept in brackish water (1-1.5%) in an aquarium (Butler, 2014).

B. belizanus is a tropical species that naturally occurs in water temperatures of 25°C - 37°C (Bussing, 1998; Froese and Pauly, 2014). Considerable research has been conducted on ex situ thermal tolerances of B. belizanus in the laboratory, though the value of these data (particularly lower lethal temperatures) in determining potential range in natural environments is speculative. Hensley and Courtenay (1980) determined lower temperature tolerances of 10-13°C, whereas Shafland and Pestrak (1982) noted a lower lethal temperature of approximately 10°C. Kerfoot (2012) acclimated neonate, juvenile and adult B. belizanus to three temperatures (20, 25, or 30°C) and determined upper and lower lethal thermal limits and temperatures at which feeding ceased. An upper lethal temperature of 38°C was consistent across life stages and acclimation temperatures. The lower lethal temperature of (9°C) of juveniles was significantly lower than other life stages (adults 11°C, neonates 13°C). Adults and juveniles ceased feeding at approximately 15°C, with no significant difference between life history stage and acclimation temperature.

Natural Food Sources

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Food SourceLife StageContribution to Total Food Intake (%)Details
All Stages >50
Gambusia All Stages >50


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Af - Tropical rainforest climate Preferred > 60mm precipitation per month
Am - Tropical monsoon climate Preferred Tropical monsoon climate ( < 60mm precipitation driest month but > (100 - [total annual precipitation(mm}/25]))
Aw - Tropical wet and dry savanna climate Preferred < 60mm precipitation driest month (in winter) and < (100 - [total annual precipitation{mm}/25])
Cs - Warm temperate climate with dry summer Tolerated Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers
Cw - Warm temperate climate with dry winter Preferred Warm temperate climate with dry winter (Warm average temp. > 10°C, Cold average temp. > 0°C, dry winters)

Latitude/Altitude Ranges

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Latitude North (°N)Latitude South (°S)Altitude Lower (m)Altitude Upper (m)
29 11

Water Tolerances

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ParameterMinimum ValueMaximum ValueTypical ValueStatusLife StageNotes
Ammonium [ionised] (mg/l) 15.7 17.5 Optimum Vega-Cendejas et al. (2013) (Native population; karstic pools in southern Mexico)
Dissolved oxygen (mg/l) 5.9 6.2 Optimum Vega-Cendejas et al. (2013) (Native population; karstic pools in southern Mexico)
Hardness (mg/l of Calcium Carbonate) 9 19 Optimum Froese and Pauly (2014)
Hardness (mg/l of Calcium Carbonate) 10 26 Optimum Butler (2014)
Nitrate (mg/l) 34.4 38.6 Optimum Vega-Cendejas et al. (2013) (Native population; karstic pools in southern Mexico)
Salinity (part per thousand) 0 35 Optimum Turner and Snelson (1984)
Salinity (part per thousand) 0 40 Optimum Froese and Pauly (2014); Robins (2014)
Salinity (part per thousand) 40 50 Harmful Belshe (1961)
Water pH (pH) 6 8 Optimum Froese and Pauly (2014)
Water pH (pH) 6.8 8.2 Optimum Butler (2014) (Aquarium environment)
Water pH (pH) 7.9 8.1 Optimum Vega-Cendejas et al. (2013) (Native population; karstic pools in southern Mexico)
Water temperature (ºC temperature) 24 29 Optimum Aquatic community (2014) (Aquarium environment)
Water temperature (ºC temperature) 26 Optimum Dawes (1991) (Aquarium)
Water temperature (ºC temperature) 10 Harmful Shafland and Pestrak (1982) (lower lethal temperature)
Water temperature (ºC temperature) 10-13 Harmful Hensley and Courtenay (1980) (lower lethal temperature)
Water temperature (ºC temperature) 25 37 Optimum Bussing (1998); Froese and Pauly (2014)
Water temperature (ºC temperature) 25 30 Optimum Butler (2014) (Aquarium environment))
Water temperature (ºC temperature) 26.1 27.6 Optimum Vega-Cendejas et al. (2013) (Native population; karstic pools in southern Mexico)
Water temperature (ºC temperature) 38 Harmful Kerfoot (2012) - all life stages); >9 (juveniles); >11 (adults); >13 (neonates); >15 (ceased feeding all life stages)

Natural enemies

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Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Egretta thula Predator Adult/Fry not specific Robins, 2014 N

Notes on Natural Enemies

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B. belizanus may be eaten by predatory fishes, piscivorous reptiles and aquatic invertebrates, and is particularly susceptible to predation by wading birds (Robins, 2014).

Garrido-Olvera et al. (2012) found that poeciliids in Mexico, including B. belizanus, were host to 22 observed helminthes, including platyhelminthes, acanthocephalans, nematodes and hirudineans.

B. belizanus has been found to host the parasites Ascocotyle leighi (Trematoda) (Hoffman, 1967) and Salsuginus neotropicalis (Mendoza-Franco and Vidal-Martínez, 2001). 

Means of Movement and Dispersal

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Natural dispersal (non-biotic)

B. belizanus can spread along rivers and canals. The euryhalinity of B. belizanus would greatly aid the species to disperse naturally. The ability of this species to spread via saline environments has been referred to as using 'saline bridges,' and was proposed as a possible mechanism to help explain the wide spread of Sander lucioperca through Europe (Brown et al., 2001). However, although the species is euryhaline, due the temperature restrictions of suitable habitat in northern Florida and elsewhere in the USA, it is reasonable to conclude that B. belizanus may remain restricted to southern Florida.

Accidental introduction

A population of B. belizanus discovered in Hillsborough County (Florida) in 1997 were thought to have escaped from a nearby ornamental fish farm (USGS NAS, 2015).

Intentional introduction

All nonindigenous populations in the USA are assumed to have resulted from the deliberate release ornamental or research specimens. B. belizanus was introduced into southern Florida in 1957, when individuals reared for medical research purposes were released into a local canal (Belshe, 1961). The population recorded in the San Antonio area of Texas was likely the result of released ornamental fish (Howells, 1992).

Pathway Causes

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CauseNotesLong DistanceLocalReferences
Escape from confinement or garden escapeA population of B. belizanus discovered in Hillsborough County (Florida) in 1997 were thought to hav Yes USGS, 2015
Intentional releaseThe population recorded in the San Antonio area of Texas was likely the result of released ornamenta Yes Yes Howells, 1992; USGS, 2015
Pet tradeThe population recorded in the San Antonio area of Texas was likely the result of released ornamenta Yes Yes Howells, 1992; USGS, 2015
ResearchIntroduced into southern Florida in 1957 when individuals reared for medical research purposes were Yes Yes Belshe, 1961

Pathway Vectors

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VectorNotesLong DistanceLocalReferences
Pets and aquarium speciesPopular aquarium species Yes Yes Robins, 2014

Impact Summary

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Cultural/amenity Negative
Environment (generally) Negative
Human health Negative

Environmental Impact

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Impact on biodiversity

B. belizanus is a piscivore that has been reported to reduce populations of Gambusia holbrooki and other native poeciliid and cyprinodontoid populations, and well as decapod crustaceans (Belshe 1961; Greenwood 2012; Harms and Turingan, 2012; Texas State University 2014).

Hensley and Courtenay (1980) considered B. belizanus to be in trophic competition with native piscivores Micropterus salmoides (largemouth bass) and Lepomis gulosus (warmouth). Miley (1978) found an 84% dietary overlap between B. belizanus and the Florida largemouth bass, Micropterus floridanus, with the predominant diet taxa consisting of fish and decapod crustaceans.

In Tampa Bay, Florida, three resident nonmigratory or potamodromous small-bodied species (Poecilia latipinna, Gambusia holbrooki and Cyprinodon variegatus) were 2-6 times less abundant or frequently occurring in the presence of, or after invasion by, B. belizanus. However, migratory species showed little evidence of negative effects, most probably because these species recruit from larger source populations and are not year-round residents of B. belizanus habitat (Greenwood, 2012).

Social Impact

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B. belizanus seriously impairs the natural control of mosquitoes in southern Florida by preying on Gambusia sp. and other native poeciliids and cyprinodontoid fishes that would otherwise eat mosquito larvae and pupae (Belshe, 1961; Greenwood, 2012; Texas State University, 2014).

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Has a broad native range
  • Abundant in its native range
  • Highly adaptable to different environments
  • Benefits from human association (i.e. it is a human commensal)
  • Fast growing
  • Has high reproductive potential
Impact outcomes
  • Altered trophic level
Impact mechanisms
  • Predation
  • Rapid growth
Likelihood of entry/control
  • Highly likely to be transported internationally deliberately
  • Difficult/costly to control


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Economic value

B. belizanus is commercially available in the USA as an ornamental aquarium fish; however, its popularity is limited due to its aggressive piscivorous nature and cannibalistic tendencies (Robins, 2014).

Uses List

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  • Laboratory use
  • Pet/aquarium trade
  • Research model

Detection and Inspection

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Photographs of B. belizanus may be viewed in Kempkes and Schäfer (1998). Distinguishing characteristics of B. belizanus are given by Rosen and Bailey (1963), Page and Burr (1991) and Howells (1992), and the species is included in identification keys of Greenfield and Thomerson (1997)

Similarities to Other Species/Conditions

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B. belizanus is unlikely to be confused with any other poeciliid due to its large size, elongated jawline and dentition (see Description).

Gaps in Knowledge/Research Needs

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Although a number of studies have considered the potential environmental impacts of introduced populations of B. belizanus, the specific mechanisms and/or ecological impacts need to be more closely examined.


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Links to Websites

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Florida Museum of Natural History - Pike killifish
University of Texas - Belonesox belizanus
USGS/NAS - Belonesox belizanus


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Philippines: Fishbase,

USA: Florida Museum of Natural History (FLMNH), Gainesville, Florida,

USA: USGS US Geological Survey, USGS National Center, 12201 Sunrise Valley Drive, Reston, VA 20192,


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15/02/15 Original text by:

Mark Maddern, University of Western Australia, Australia

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