Fish populations -- Florida, Poeciliidae


The pike killifish, Belonesox belizanus Kner, is the largest member of the live-bearing family Poeciliidae. The species is native to Central America, and was introduced into Dade County, Florida in 1957. B. belizanus is primarily piscivorous, and has been identified as a potential ecological "problem" species for Florida due to its heavy predation on small native fishes, especially the mosquitofish (Gambusia affinis). The population structure and reproduction of the Florida population were investigated in this study from field samples and aquarium observations. The mean standard length (SL) of mature females was about 103 mm. Most females larger than 75 mm SL contained yolked developing ova, fertilized eggs, or embryos. Mature males averaged about 72 mm SL, and the majority of males larger than 55 mm SL were mature. The sex ratio of mature fish was significantly skewed in favor of females, while immature fish did not differ significantly from a 1:1 sex ratio. The average brood size of field-caught females was about 99, and there was a significant positive correlation of brood size with size of the parent female. The gross morphology of embryological development was described. Although mature unfertilized eggs, abnormal embryos, and degenerating embryos from a previous brood were found at a low frequency in broods of normal embryos, no evidence of superfetation was found. Sizes and weights of embryos and neonates were the largest reported for the family. There was a significant decrease in mean embryo weight as development proceeded, indicating that developing embryos received little or no nutrient input from the maternal system after fertilization. The average interbrood interval of aquarium-held females was 42 days, and females were capable of storing viable sperm. Field-caught females were capable of year-round reproduction. Laboratory-born neonates were immediately piscivorous, and exhibited distinctive behaviors associated with filling of the swim bladder and with avoiding detection by predators. Comparisons of the reproductive patterns of B. belizanus with other members of the family Peociliidae are discussed.


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Graduation Date

Summer 1981


Snelson, Franklin F.


Master of Science (M.S.)


College of Arts and Sciences

Degree Program





56 p.




Public Domain

Length of Campus-only Access


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Masters Thesis (Open Access)



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Snelson, Franklin F. [VIAF]

Snelson, Franklin F. [LC]

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