Nursery habitats for ladyfish, Elops saurus, along salinity gradients in two Florida estuaries

Ladyfish, Elops saurus, are recognized as an estuarine-dependent species, a lthough no published study has described how ladyfish use estuarine habitat s. This study found ladyfish to be common throughout Tampa Bay and Indian R iver Lagoon, Florida. In both estuaries, metamorphosing larvae were collect ed during several months of the year, but they were most abundant in spring . Length-frequency analyses suggested that age-0 ladyfish grew from 20-30 m m to 200-300 min standard length during their first year and that at least three age classes were present throughout the year. Age-0 ladyfish followed an ontogenetic migration with regard to salinity, They entered estuaries a s metamorphosing larvae and became concentrated in waters of lower than med ian salinity for both estuaries (23-25 ppt). In Tampa Bay, which had a grea ter range of salinity than the Indian River Lagoon, age-0 ladyfish were fou nd principally in mesohaline and oligohaline areas; in the Indian River Lag oon, age-0 ladyfish were found in mesohaline and polyhaline waters. In autu mn, age-0 ladyfish moved back to higher salinities, into lower parts of the estuaries, and even out to beaches along the Gulf of Mexico. These field o bservations are consistent with the hypothesis that ladyfish depend on estu aries, specifically positive estuaries, i.e. where freshwater input exceeds evaporative processes. However, published studies also demonstrate that la rval ladyfish can metamorphose and juveniles can survive in hypersaline wat ers; therefore negative estuaries may also serve as suitable nursery habita t. It is not clear how salinity affects ladyfish growth and mortality, and further research should clarify how different types of estuaries (i.e. posi tive versus negative) contribute to maintaining populations of this fishery species.