Comparative life history of female mosquito fish, Gambusia affinis, in tidal freshwater and oligohaline habitats

Abstract

SynopsisFemale Gambusia afinis were collected from low salinity/near-neutral pH and tidal freshwater/low pH localities to document life history variation between these two habitats. Mosquitofish were 2.7 times more abundant in low salinity/near-neutral pH (2.37 5 0.72ppt; 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 afinis may have a greater reproductive effort in low salinity/near-neutral pH environments than in freshwater/low pH habitats.

Life history variation along a salinity gradient in coastal marshes

“…We found significant variation in all traits examined, except for the body condition of H. formosa males and females and female P. latipinna (Table 3). Our results are congruent with those of Stearns & Sage (1980) and Brown-Peterson & Peterson (1990) for G. affinis and Trexler & Travis (1990) for P. latipinna. Both the current study and the earlier reports found that females from higher salinity habitats exhibited greater reproductive allotment and fecundity than females collected in nearby lower-salinity sites.…”

“…We found lower levels of body condition, lowered GSI, and lowered fecundity for G. affinis in fresh marshes, where these fish were most abundant, indicating that greater abundance did not correspond with better condition and higher reproductive capacity. Limited evidence exists from other studies to suggest that freshwater would be more stressful to Gambusia affinis than those salinities observed in intermediate marshes (Stearns & Sage 1980, Brown-Peterson & Peterson 1990). Additionally, Akin & Neill (2004) did report an increase in respiration rates in G. affinis at 0 ppt compared to at 10 ppt (though they did not feel this increased respiration would be stressful to the fish).…”

Reproductive Cycle of a Population of the Guaru, Phallocerus caudimaculatus (Poeciliidae), in Southeastern Brazil

“…Females that mature too late may not survive to reproduce (Kusano, 1982). For many fish species, as also shown in the present study, clutch size is positively correlated with body size of females (Reznick & Miles, 1989;Brown-Peterson & Peterson, 1990). Thus, according to the environmental conditions that a population is facing there are different selective pressures upon the individuals: they may reproduce early with small body size and small clutch, or they may delay sexual maturation and grow to a large body size with a large clutch (see discussion in Kusano, 1982).…”

Life-history traits of the invasive fish Gambusia ­holbrooki in saline streams (SE Iberian Peninsula): Does salinity limit its invasive success?

“…A similar population structure of G. holbrooki inhabiting watercourses of different degrees of salinity has already been shown by Alcaraz & García-Berthou (2007), although the present study extends the salinity range studied in a natural population up to 49.5 g l -1 . These results point to the good adap tation of the species to environments of different quality (Specziár 2004), as has been described for G. affinis (Brown-Peterson & Peterson 1990).…”