Comparative life history of female mosquito fish,Gambusia affinis,in tidal freshwater and oligohaline habitats |
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Authors: | Nancy Brown-Peterson Mark S Peterson |
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Institution: | (1) Florida Department of Natural Resources, Bureau of Aquatic Preserves, 4842 South U.S.Hw., 1, Fort Pierce, FL, 34982, U.S.A.;(2) Harbor Branch Oceanographic Institution, Inc., 5600 Old Dixie Highway, Fort Pierce, FL, 34946, U.S.A.;(3) Present address: Department of Biological Sciences, Mississippi State University, P.O. Drawer GY, Mississippi State, MS, 39762, U.S.A. |
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Abstract: | Synopsis Female Gambusia affinis were collected from low salinity/near-neutral pH and tidal freshwater/low pH localities to document life history variation
between these two habitats. Mosquito fish were 2.7 times more abundant in low salinity/near-neutral pH (2.37 ± 0.72 ppt; pH
= 5.73 ± 0.11) than in tidal freshwater/low pH (0.27 ± 0.19 ppt; pH = 4.46 ± 0.18) habitats in Old Fort Bayou, a black-water
tidal river of the Biloxi Bay estuary, Mississippi. Fish were common in both areas from June 1985 through February 1986. There
were no significant differences between habitats in the length-weight relationships during the reproductive season with the
exception of February. However, there were significant differences in life histories, although the areas were only 4 km apart.
Ovarian recrudescence was observed in fish from both areas in February, but ovaries of low salinity fish were more developed
than ovaries of freshwater fish. All fish from both areas had regressed ovaries by late September. The monthly slopes of the
brood size vs. standard length regressions were significantly different between areas throughout the reproductive season with
the exception of June. Although freshwater fish produced heavier tail-free embryos, fish from low salinity had significantly
higher GSI values and brood size throughout the reproductive season. These observations suggest that Gambusia affonis may have a greater reproductive effort in low salinity/near-neutral pH environments than in freshwater/low pH habitats. |
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Keywords: | Fecundity Brood size Length-weight relationship Life history theories Salinity pH Reproductive biology |
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