Life-history characteristics of eleotrid fishes of the western hemisphere, and perils of life in a vanishing environment

The term amphidromous was coined (Myers in Copeia 1949:89–97, 1949b) to describe diadromous life histories that include migrations, not associated with reproduction, that are between fresh and marine waters. This concept has facilitated evaluations of life cycles among a number of groups of fishes including some belonging to the family Eleotridae. Information was gathered on life history patterns of eleotrid fish species that have been recorded from both fresh and brackish or marine waters of the east and west coasts of North, Middle, and South America, including adjacent islands, seeking evidence of diadromy and especially of amphidromy. Convincing evidence was found of diadromy in the life cycles of four species from the east coast (with another two species possibly in this category), and of three species from the west coast of the Americas and adjacent islands. However, there was convincing evidence of amphidromy in only one species from the east coast and adjacent islands, with another three species or species populations possibly in this category, and in three species from the west coast and adjacent islands. It seems possible from the available information that there may be variation among populations in life cycles of some of these species. However, it remains for the use of modern techniques to allow more definitive determinations of life history patterns of these eleotrid species populations. Serious concern exists with respect to the conservation of all diadromous species because of the worldwide emphasis on river manipulations, especially of dam construction. Resident diadromous organisms are being impeded in their migrations, and thus imperiled in their potential for survival, depending on the nature of river alterations and the abilities of the organisms to cope with them.