Salinity relationships in a freshwater population of eastern mosquitofish


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Tolerance limit to elevated ambient salinity, and plasma osmotic regulatory capabilities were evaluated in a freshwater population of Gambusia holbrooki. The upper tolerance limit of ambient salinity was found to be 25‰. Plasma osmotic concentrations trended sharply upward with increasing salinity, but in a stepwise fashion, unlike patterns in related, but more euryhaline species. These laboratory observations are consistent with field observations that natural populations of G holbrooki are generally restricted to fresh and dilute brackish waters.