Belonesox belizanus

pike killifish

Type Locality

Belize, Belize (Kner 1860).

Etymology/Derivation of Scientific Name

Belon (Greek), meaning “a dart, arrowhead, needle”; beli (Greek), meaning “a dart, sting”.

Synonymy

Characters

Maximum size: 200 mm SL (Hensley and Courtenay 1980). This species is the giant of the livebearer family (Connaly 1968; Page and Burr 1991).

Coloration: Dark olive above fading to white below; several rows of black spots on side; one of more longitudinal rows of black spots on the body; black spot at the caudal case (Connaly 1968; Stevenson 1976; Page and Burr 1991). Young have a single dark band around their mid-side they use to camouflage themselves from predators, including their parents, by mimicking foliage/twigs; species shows little secondary sexual coloration (Breder and Rosen 1966; Turner and Snelson 1984; Hensley and Courtenay 1980).

Counts: Usually 52-63 lateral scales; usually 8-9 dorsal rays (Page and Burr 1991).

Body shape: Thin (Bussing 1998). Snout long (Stevenson 1976).

Mouth position: "Pickerel-like mouth" (Stevenson 1976). Long jaws form pointed beak (Page and Burr 1991). Large teeth on jaws (Hensley and Courtenay 1980); substantial curve to both the lower and upper jaws does not permit this species to close them (Connaly 1968). Length of upper jaw (from crease at base, dorsally) greater than width of gape (Stevenson 1976).

External morphology: Dorsal fin origin well behind anal fin origin; small scales (Connaly 1968; Stevenson 1976; Page and Burr 1991); eye reaching to dorsal contour of head (Stevenson 1976). Rather prominent gonopodium marks male at once (Breder and Rosen 1966; Connaly 1968).

Distribution (Native and Introduced)

U.S. distribution: Native to Mexico and Central America, releases of research and home aquariums have led to widespread populations in United States. Established in canals in southeastern Dade and Monroe counties, Florida; abundant at Florida localities after fish used in experimental research was released into a canal in Dade Co., Florida, in November 1957 (Belshe 1961; Miley 1978; Hensley and Courtenay 1980; Page and Burr 1991).

Texas distribution: A previously established population, which was introduced in the early 1960’s (Barron 1964) into the San Antonio River, San Antonio, Texas, is apparently no longer extant (Hubbs et al. 1978; Hensley and Courtenay 1980; Edwards 2001).

Abundance/Conservation status (Federal, State, NGO)

Habitat Associations

Macrohabitat: Found in neither fast nor stagnant waters, rather along the banks of slow-moving streams, mangrove and weedy swamps, and inlets into salty bays (Connaly 1968); weedy canals (Page and Burr 1991).

Mesohabitat: Seem to prefer dirty to clean waters, and well planted to open ones. Species has been found in areas completely covered with algae, and in cattle watering holes (Connaly 1968). Able to live in water with low oxygen concentration; will tolerate seawater; has lower temperature tolerances (10-13°C; Hensley and Courtenay 1980). Shafland and Pestrak (1982) note lower lethal temperature of 9.7 degrees C. Laboratory studies show that this species lives indefinitely in sea water and survives salinities of 40-50 ppt for limited periods (Belshe 1961).  Turner and Snelson (1984) found permanent populations reproducing at salinities that ranged from zero to at least 35 ppt.

Biology

Spawning season: Pregnant and gravis females found in all months, but frequency of reproductively active individuals was reduced in winter (Turner and Snelson 1984).

Spawning habitat:

Reproductive strategy: Livebearer (Page and Burr 1991). Males repeatedly conduct particular behavioral acts when in the presence of females. Females do not conduct this suite of behaviors. Courting male will position himself in front of, and perpendicular to a female, fanning his fins and gonopodium in her direction prior to attempting to mate.  Male coloration becomes more vibrant during a display, which is often followed by mating attempts (Horth 2004).

Fecundity: Turner and Snelson (1984) noted that brood size was about 99, and there was a significant positive correlation of brood size with size of parent; diameters of mature, fertilized eggs (clear golden-yellow yolk, with fat droplets coalesced at the animal pole) ranged from 2.85 to 3.67 mm, with a mean of 3.29 mm. Scrimshaw (1946) and Wourms (1981) reported egg size ranging from 4.1-8 mm in diameter. Females are known to produce up to 153 young (Breder and Rosen 1966). In south Florida, Belshe (1961) found brood sizes ranging from 48-225 with a mean of 94. The large brood sizes reported and the ability to reproduce year-round at approximately 40-day intervals, indicate this species is among the most fecund of poeciliid fishes (Turner and Snelson 1984).

Age/Size at maturation: Turner and Snelson (1984) noted that the majority of females75 mm SL or larger, and all females larger than 105 mm SL contained either yolked ova, fertilized eggs, or embryos.  Three laboratory born and reared females delivered their first broods at 163, 177 and 211 days of age, at respective sizes of 90, 101, and 108 mm SL. The majority of males larger than 55 mm SL were mature. Gonopodia of three laboratory born and reared males became fully differentiated at the following approximate ages and sizes: 80-85 days (61 mm SL), 102-105 days (63 mm SL), and 138-140 days (64 mm SL).

Migration:

Growth & Population structure: Males are far smaller than females (Breder and Rosen 1966; Hensley and Courtenay 1980; Rauchenberger 2005). Larger than most fishes of this family, young are nearly three-quarters of an inch in length at birth (Breder and Rosen 1966). Turner and Snelson (1984) noted that mature females ranged from 56-148 mm SL, with a mean of about 103 mm SL; mature males ranged from 51-106 mm SL, with a mean of about 72 mm SL. Immature males were 27-48 mm SL and transforming males were 38-98 mm SL. Mature specimens from all sites were pooled and females outnumbered males by a ratio of 2.01:1; sex ratio of immature fish did not differ significantly from 1:1 ratio when analyzed by site or by total pool sample.

Longevity:

Food habits: Piscivore; the strong teeth and beaklike jaws are commensurate with its exclusively carnivorous diet (Hensley and Courtenay 1980). Based on laboratory observations, species immediately piscivorous, vigorously pursuing, capturing, and consuming live brine shrimp and newborn mosquitofish and mollies within one day of their (B. belizanus) birth; juvenile B. belizanus occasionally preyed upon their siblings; adults only accepted live fishes as food; females rarely ate their newborn young. Incidental observations of field-caught B. belizanus indicated that mosquitofish, mollies, and other pike killifish were the most common food items (Turner and Snelson 1984). Able to feed on new-born guppies (Poecilia) and platyfishes (Xiphophorus) a minute or two after emerging from the female; motionless, surface floating fry while parents were present in an aquarium and their immediate descent and feeding upon parent removal suggest that the behavior may reduce the chance of parental cannibalism (Breder and Rosen 1966).

Phylogeny and morphologically similar fishes

Host Records

Trematoda: Ascocotyle leighi, larval form (Hoffman 1967). Salsuginus neotropicalis (Mendoza-Franco and Vidal-Martínez 2001).

Commercial or Environmental Importance

In Florida, this species seriously impairs the natural control of mosquitoes by preying on Gambusia affinis (western mosquitofish) and other native poeciliid and cyprinodontid fishes. This species in trophic competition with Micropterus salmoides (largemouth bass) and Lepomis gulosus (warmouth; Hensley and Courtenay 1980).

References

Barron, J.C. 1964. Reproduction and apparent over-winter survival of the suckermouth armored catfish, Plecostomus sp., in the headwaters of the San Antonio River. Texas J. Sci. 16:449.

Belshe, J.F. 1961. Observations of an introduced tropical fish (Belonesox belizanus) in Southern Florida. M.S. Thesis, University of Miami, Coral Gables. 71 pp.

Breder, C. M., Jr. and D. E. Rosen. 1966. Modes of Reproduction in Fishes. Natural History Press, Garden City, 941 pp.

Bussing, W. A. 1998. Freshwater Fishes of Costa Rica. International Journal of Tropical Biology and Conservation. San Jose, Costa Rica.Vol. 46 Suppl. 2.

Connaly, H. 1968. The pike livebearer. Aquarium 2: 45-50.

Edwards, R.J. 2001. Ecological profiles for selected stream-dwelling Texas freshwater fishes III. Report to the Texas Water Development Board. 59 pp.

Hensley, D.A. and W.R. Courtenay, Jr. 1980. Belonesox belizanus (Kner) Pike Killifish pp. 537 in D.S. Lee et al. Atlas of North American Freshwater fishes. N.C. State Mus. Nat. Hist., Raleigh, i-r+854.

Hoffman, G.L. 1967. Parasites of North American Freshwater Fishes. University of California Press. Berkeley, 486 pp.

Horth, L. 2004. A brief description of the courtship display of male pike killifish (Belonesox belizanus). Florida Scientist 67(2):159-165.

Hubbs, C., T. Lucier, G.P. Garrett, R.J. Edwards, S.M. Dean, and E. Marsh. 1978. Survival and abundance of introduced fishes near San Antonio, Texas. Texas Journal of Science 30:369-376.

Kner, R. 1860. Uber *Belonesox belizanus*, nov. gen. et. spec., aus der Familie der Cyprinodonten. Sitzungsber. Akad. Wiss. Wien 40:419-22.

Mendoza-Franco, E.F., V.M.Vidal-Martínez. 2001. Salsuginus neotropicalis n. sp. (Monogenea: Ancyrocephalinae) from the pike killifish Belonesox belizanus (Atheriniformes: Poeciliidae) from southeastern Mexico. Systematic Parasitology. 48(1): 41-45.

Miley, W.W., II. 1978. Ecological impact of the pike killifish, Belonesox belizanus Kner (poeciliidae), in southern Florida, M.S. Thesis. Florida Atlantic University, Boca Raton. 55 pp.

Rauchenberger, M. 2005. Artificial Key to Mexican Poeciliidae. pp. 218-219 in Miller, R. R. et al. 2005. Freshwater Fishes of Mexico. The University of Chicago Press, Chicago, 490 pp.

Scrimshaw, N.S. 1946. Egg size in Poeciliid fishes. Copeia 1946(1):20-23.

Shafland, P.L. and J.M. Pestrak. 1982. Lower lethal temperatures of fourteen non-native fishes in Florida. Env. Biol. Fish. 7: 149-156.

Stevenson, H. M. 1976. Vertebrates of Florida. University Presses of Florida, Gainesville. 607 pp.

Turner, J. S., F. F. Snelson, Jr. 1984. Population structure, reproduction and laboratory behavior of the introduced Belonesox belizanus. Environmental Biology of Fishes. 10(1-2):89-100.

Wourms, J.P. 1981. Viviparity: the maternal-fetal relationship in fishes. Amer. Zool. 21:473-515.