Physicochemical environments and tolerances of cyprinodontoid fishes found in estuaries and salt marshes of eastern North America

Abstract

Individuals of 28 species of cyprinodontoid fishes have been reported from estuaries/salt marshes of the Atlantic and Gulf coasts of North America. Some species show limited latitudinal distributions and/or occupy a limited range of habitats; others are widely distributed and/or occupy a wide range of habitats. A literature survey was made of conditions of water temperature, dissolved-oxygen (DO) concentrations, and salinities at sites where individuals of each species had been collected, and of laboratory-determined tolerances or lethal limits and other responses to those abiotic conditions. Individuals of Cyprinodon variegatus showed the widest overall range of tolerance of environmental temperatures, −1.9–45.4°C, with Gambusia rhizophorae showing the highest lower temperature-tolerance limit, 17°C. The only species highly sensitive to hypoxia was Floridichthys carpio, which showed “stress” at DO levels of 6–8 mg kg⁻¹. All showed use of aquatic surface respiration, except for Kryptolebias marmoratus, which uses aerial respiration in the presence of H₂S, and/or under hypoxic conditions. Individuals of C. variegatus were found to tolerate ambient salinities ranging from < 0.5 to 125.2, or higher, and several species of the genus Fundulus were found to tolerate concentrations ranging from Fundulus heteroclitus. Suggestions were made, based on existing information, as to species that would be most likely to show altered population distributions resulting from continued global warming. These included five species that have tropical/subtropical, or subtropical/temperate distributions. Also, a few others were included that show extensive latitudinal distributions, most extending northward into cooler temperate regions of the Atlantic coast. At present, none of these species has shown a range alteration that can be attributed to global warming.