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Belonesox

Physical description: An elongated species with a flat-back profile. The lower jaw is longer than the upper, and turned up towards the water surface. The eye is large and the dorsal fin is located far back on the body. The back is light brown to olive and the flanks are darker with a greenish iridescence. On the flanks are a series of small black spots that often form a broken line. The belly is yellowish white. At the base of the caudal fin is a dark spot. The fins are otherwise colorless. Size/Length: Females to 9" (23 cm); males to 4" (10 cm) Similar species: None Habitat: Central America; inhabits still marshes and lakes from Honduras to Southern Mexico S: top Aquarium: A tank measuring 40" (101 cm) with a capacity of 45-55 gallons is sufficient (170-209 l). The tank should be heavily planted with a partial cover of floating plants. Leave open swimming areas and use a tight-fitting cover. The filter should be strong but create little current. Water chemistry: pH 6.8-8.2 (7.5), 10-26 dH (15), 77-86°F (25-30°C). Suggest a 1-1.5% addition of salt. This can be accomplished by adding 7.5-11 TSP. of slat to every 10 gallons (10-15 g/10 L). Social behavior: A predatory species that will feed on smaller fish. Keep in a species tank or combine with other large species. Older fish become more aggressive with age. A shy fish that at first hides among plants. Suggested companions: Cichlasomines species, large Xiphophorus sp (over 4.7" or 12 cm in length), Loricarids, Doradids. FOOD: Live; fish, earthworms, insects, insect larvae, crustaceans; beef heart; occasionally pellets. SEX: Female is significantly larger and lack the gonopodium of the male. Breeding techniques: Spawning is easiest with the addition of salt. As many as 120 live young are born. These measure from 0.5" to 1" (1.3-2.5 cm) in length, depending on the size and condition of the female. The female will not each the young, although they should be removed to a rearing tank of their own. The young grow quickly when fed on a diet of Cyclops and Artemia, and frequent partial water changes are administered. The young can later be fed small guppies. The young must be frequently sorted for size so cabalism does not occur. Breeding potential: Breeding is easy in a large species tank. Remarks: The Pike Livebearer is the only species of the genus Belonesox. Difficulty of care: This predatory livebearer is best kept in a species tank. It requires a diet of live foods, and proper water conditions should be maintained.

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Scientific Name: Belonesox belizanus

Common Name: Pike killifish, pike topminnow, pike livebearer, ulumina gaspara, pepesca gaspar

Distinguishing Features:

Pike killifish can easily be identified by their long jaws and large teeth. The origin of the dorsal fin is posterior to the origin of the anal fin. Their color is dark olive dorsally fading to white ventrally. Several rows of black spots are present on their sides and a black spot is present on their caudal peduncle. There are 53-63 scale rows in a lateral series. Taxonomy: The population established in Florida belongs to the subspecies Beloneox belizanus maxillosus (Turner and Snelson, 1984).

Biology:

This species prefers hard, alkaline waters (Sakurai et al., 1992). Salinity Tolerance: Over their native range, pike killifish are found along the banks and in the upper water levels of slow moving fresh water streams, in the brackish waters of mangrove and reed swamps, and around inlets of salty bays (Sterba, 1983; Turner and Snelson, 1984; Bussing, 1987; Sakurai et al., 1992). Courtney et al. (1984), reported specimens established in saline cooling canals (40 ppt) in Dade county Florida. There are reports of tolerance to salinity's of 50 ppt over brief periods (Belshe in Courtenay et al., 1974; Turner and Snelson, 1984). Permanent populations have been found breeding in salinity's of up to 35 ppt (Turner and Snelson, 1984). The euryhaline nature of pike killifish has facilitated their spread throughout Florida.

Temperature Tolerance: Shafland and Pestrak (1982) reported a lower lethal temperature of 9.7°C for this species. In Florida reproduction appears not to be limited by temperature, occurring throughout the year (Turner and Snelson, 1984). Courtney et al. (1974), believed temperature would not be a limiting factor for this species in Florida.

Reproduction and Fecundity: Turner and Snelson (1984) reviewed the population structure and breeding habits of pike killifish established in Florida. These fish are live-bearers which breed throughout the year. Females are larger than males. They mature at approximately 75 mm and grow to 200 mm, whereas males mature at approximately 55 mm and grow to 120 mm. In addition females have a yellow or occasionally orange coloration at the base of their anal fin (Riehl and Baensch, 1991). Females are capable of storing sperm for at least 47-56 days. Gestation takes between 30 and 50 days (Sterba, 1983). Egg diameter ranges from 2.85 mm to 3.67 mm with a mean of 3.29 mm. Typically 100, but up to 322 eggs are spawned per brood (Villa, 1970; Sterba, 1983; Turner and Snelson, 1984; Sakurai et al., 1992). Females can produce broods approximately every 40 days. Newly hatched fish measure between 14.3 and 17.7 mm, with a mean of 16.3 mm. Fry of this species are known to cannibalize each other (Axelrod et al., 1971; Sakurai et al., 1992).

Among mature fish, females are significantly more numerous than males (Turner and Snelson, 1984).

Trophic Interactions: This species is primarily piscivorus and highly aggressive towards other species. Pike killifish are ambush predators, they lurk behind plants, roots, and rocks and strike violently at their prey (Axelrod et al., 1971; Sterba, 1983). Their main prey items include poeciliids, cyprinodontids, and smaller conspecifics (Turner and Snelson, 1984). However, this species is also a favorite prey of larger predators (Shafland, 1996). Within one day of their birth, young begin feeding on small crustaceans and new born fish. Both young and adults show interest only in moving prey (Villa, 1970; Turner and Snelson, 1984). Turner and Snelson (1984) found specimens under experimental conditions ignored live insects, tadpoles and small frogs, accepting only live fish as food.

Pike killifish exert strong pressure on small native fish, particularly poeciliids and cyprinodontids, through direct predation (Lachner, 1970; Courtenay and Robins, 1973; Courtenay et al., 1974; Lee et al., 1980; Miley in Turner and Snelson, 1984; Shafland, 1996).

Maximum Size:

This species is the largest member of the family Poeciliidae. Typically males grow to between 100 and 120 mm whereas females grow to between 150 and 200 mm (Lachner et al., 1970; Lee et al., 1980; Sterba, 1983; Turner and Snelson, 1984; Page and Burr, 1991; Riehl and Baensch, 1991; Shafland, 1996).

Distribution:

Pike killifish naturally occur on the Atlantic slope of Central America from Laguna San Julian, northwest of Cuidad Veracruz, Mexico to Costa Rica (Miller, 1966; Courtenay et al., 1984; Bussing, 1987; Sakurai et al., 1992). In the Gulf of Mexico ecosystem, they are established in southeastern Florida (Lee et al., 1980; Courtney et al., 1991; Shafland, 1996). Museum records exist for Collier, Dade, and Monroe counties. At one time this species occurred in the San Antonio River, Texas, but they are no longer found there (Hubbs, 1978; Lee et al., 1980).Pike killifish naturally occur on the Atlantic slope of Central America from Laguna San Julian, northwest of Cuidad Veracruz, Mexico to Costa Rica (Miller, 1966; Courtenay et al., 1984; Bussing, 1987; Sakurai et al., 1992).

In the Gulf of Mexico ecosystem, they are established in southeastern Florida (Lee et al., 1980; Courtney et al., 1991; Shafland, 1996). Museum records exist for Collier, Dade, and Monroe counties. At one time this species occurred in the San Antonio River, Texas, but they are no longer found there (Hubbs, 1978; Lee et al., 1980).

Interest to Fisheries:

Pike killifish are of no value as a food fish. However, they may compete with native juvenile sport fish, such as centrarchids, for prey. B. belizanus exerts considerable pressure on natural populations of small forage and bait fish, especially poeciliids and cyprinodontids, through direct predation

Current Status of this Species in the Gulf of Mexico Ecosystem:

Pike killifish were introduced into a canal along SW Eighty-seventh avenue, in Dade county, Florida, in November of 1957, after termination of a research project (Courtenay and Robins, 1973; Courtenay et al., 1974; Courtenay et al., 1984; Turner and Snelson, 1984). This stock originated from Progreso, Yucatan in Mexico (Turner and Snelson, 1984). Attention was drawn to the potential impact of their establishment as early as 1965 (Rivas, 1965). Pike killifish were first reported from Texas in Brackenridge Park, San Antonio, Bexar county (Barron, 1964). They were probably introduced there by commercial or recreational aquarists (Howells, 1992). Hubbs et al. (1978) reported this species was eradicated from Texas.

In Florida, pike killifish are typically found in shallow waters rich in vegetation or in mangrove swamps; they are seldom present in open waters (Turner and Snelson, 1984; Page and Burr, 1991). They can readily tolerate habitats deficient in oxygen (Lee et al., 1980; Page and Burr, 1991). Pike killifish continue expanding their range in this state(Shafland, 1996).

Potential Impacts:

Lachner et al. (1970) qualified pike killifish as: "...an active, predaceous carnivore on small aquatic life, including young fishes, and (which) serves only as a detriment to our native fauna.". They appear to be the only non-indigenous poeciliid having a significant detrimental effects on the native biota of Florida (Courtenay et al., 1974). Pike killifish exert severe pressure on small native fishes, especially cyprinodontids and poeciliids (Lachner, 1970; Courtney and Robins, 1973; Courtney et al., 1974; Lee et al., 1980; Miley in Turner and Snelson, 1984; Shafland, 1996). They have reportedly eliminated mosquito fish, Gambusia affinis, from some canals through direct predation (Courtenay and Robins, 1973). Their predation on mosquitofish as well as on other cyprinodontiform fish, impairs natural mosquito control in southern Florida (Lee et al., 1980). Pike killifish compete for prey with native piscivorus fish such as Micropterus salmoides and Lepomis gulosus (Lee et al., 1980). Additionally they have been reported as highly detrimental to various marsh communities in Florida, naturally impoverished in ichthyophagous species (Shafland, 1996).

Recommendations:

Records of this species should be reported to museums or the National Aquatic Nuisance Species database, preferably saving the specimen for positive identification, if at all possible.

References:

Astorqui, I. 1971. Peces de la cuenca de los grandes lagos de Nicaragua. Revista de Biologia Tropical 19(1/2):7-57.

Axelrod, H.R., C.W. Emmens, D. Sculthorpe, W.V. Winkler, and N. Pronek. 1971. Exotic Tropical Fishes. TFH Publications, Inc. Jersey City, NJ.

Bussing, W. A. 1987. Peces de las aguas continentales de Costa Rica. Editorial de la Universidad de Costa Rica, San Jose. 221 pp.

Courtenay, W. R., Jr. and C. R. Robins. 1973. Exotic aquatic organisms in Florida with emphasis on fishes: A review and recommendations. Transactions of the American Fisheries Society 102(1):1-12.

Courtenay, W. R., Jr., D. A. Hensley, J. N. Taylor, and J. A. McCann. 1984. Distribution of exotic fishes in the continental United States. Pages 41-77 in W. R. Courtenay, Jr., and J. R. Stauffer, Jr., editors. Distribution, biology and management of exotic fishes. Johns Hopkins University Press, Baltimore, MD.

Courtenay, W. R., Jr., D. P. Jennings, and J. D. Williams. 1991. Appendix 2, exotic fishes. Pages 97-107 in Robins, C. R., R. M. Bailey, C. E. Bond, J. R. Brokker, E. A. Lachner, R. N. Lea, and W. B. Scott, editors. Common and scientific names of fishes from the U.S. and Canada. Special Publication 20, American Fisheries Society, Bethesda, Md..

Courtenay, W. R., Jr., H. F. Sahlman, W. W. Miley, II, and D. J. Herrema. 1974. Exotic fishes in fresh and brackish waters of Florida. Biological Conservation 6(4):292-302.

Howells, R. G. 1992. Annotated list of introduced non-native fishes, mollusks, crustaceans and aquatic plants in Texas waters. Texas Parks and Wildlife Department, Management Data Series 78, Austin, TX. 19 pp.

Hubbs, C., T. Lucier, G. P. Garrett, R. J. Edwards, S. M. Dean, E. Marsh, and D. Belk. 1978. Survival and abundance of introduced fishes near San Antonio, Texas. Texas Journal of Science 30(4):369-376.

Lachner, E. A., C. R. Robins, and W. R. Courtenay, Jr. 1970. Exotic fishes and other aquatic organisms introduced into North America. Smithsonian Contributions to Zoology 59:1-29.

Lee, D. S., C. R. Gilbert, C. H. Hocutt, R. E. Jenkins, D. E. McAllister, and J. R. Stauffer, Jr. 1980. Atlas Of North American Freshwater Fishes. Publication No. 1980-12 Of The North Carolina Biological Survey. North Carolina State Museum Of Natural History. 854 Pp.

Miller, R. R. 1966. Geographic Distribution Of Central American Freshwater Fishes. Copeia 1966(4):773-803.

Page, L. M., and B. M. Burr. 1991. A field guide to freshwater fishes of North America north of Mexico. The Peterson Field Guide Series, volume 42. Houghton Mifflin Company, Boston, MA.

Riehl, R., and H.A. Baensch. 1991. Aquarium Atlas. Mergus. Melle, Germany. 992 pp.

Rivas, L. R. 1965. Florida fresh water fishes and conservation. Quarterly Journal of the Florida Academy of Science 28(3):255-258.

Sakurai, A., Y. Sakamoto, and F. Mori. 1993. Aquarium Fish Of The World: The Comprehensive Guide To 650 Species. English Translation By Takeshi Shimizu With Neil M. Teitler. Edited By P. V. Loiselle. Chronicle Books. San Francisco. 288 Pp.

Shafland, P. L. 1996. Exotic Fishes of Florida-1994. Reviews in Fisheries Science 4(2):101-122.

Shafland, P. L. and J. M. Pestrak. 1982. Lower lethal temperatures for fourteen non-native fishes in Florida. Environmental Biology of Fishes 7(2):139-156.

Sterba, G. 1983. The Aquarium Fish Encyclopedia. The MIT Press. Cambrige, Massachusetts. 605 pp.

Turner, J.S., and F.F. Snelson, Jr. 1984. Population Structure, Reproduction And Laboratory Behavior Of The Introduced Belonesox Belizanus (Poeciliidae) In Florida. Environmental Biology Of Fishes 10(1/2):89-100.

Villa, J. 1970. La Pepesca Gaspar, otro pez desconocido del Gran Lago. Medicina y Cultura 14:12-14.

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