443 
Nursery habitats for ladyfish, Elops saurus, 
along salinity gradients in two Florida estuaries 
Richard S. McBride 
Timothy C. MacDonald 
Richard E. Matheson Jr. 
David A. Rydene 
Peter B. Hood 
Florida Marine Research Institute 
100 Eighth Avenue SE 
St. Petersburg, Florida 33701-5095 
E-mail address (for R. S McBride): richard.mcbride@fwc state. fl. us 
Abstract— Ladyfish, Elops saurus , are 
recognized as an estuarine-dependent 
species, although no published study 
has described how ladyfish use estua- 
rine habitats. This study found ladyfish 
to be common throughout Tampa Bay 
and Indian River Lagoon, Florida. In 
both estuaries, metamorphosing larvae 
were collected 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 mm to 200-300 mm standard 
length during their first year and that 
at least three age classes were present 
throughout the year. Age-0 ladyfish fol- 
lowed an ontogenetic migration with 
regard to salinity. They entered estu- 
aries as metamorphosing larvae and 
became concentrated in waters of lower 
than median salinity for both estuar- 
ies (23-25 ppt). In Tampa Bay, which 
had a greater range of salinity than 
the Indian River Lagoon, age-0 ladyfish 
were found principally in mesohaline 
and oligohaline areas; in the Indian 
River Lagoon, age-0 ladyfish were found 
in mesohaline and polyhaline waters. In 
autumn, 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 observa- 
tions are consistent with the hypothesis 
that ladyfish depend on estuaries, spe- 
cifically positive estuaries, i.e. where 
freshwater input exceeds evaporative 
processes. However, published studies 
also demonstrate that larval ladyfish 
can metamorphose and juveniles can 
survive in hypersaline waters; therefore 
negative estuaries may also serve as 
suitable nursery habitat. It is not clear 
how salinity affects ladyfish growth and 
mortality, and further research should 
clarify how different types of estuaries 
(i.e. positive versus negative) contrib- 
ute to maintaining populations of this 
fishery species. 
Manuscript accepted 19 December 2001 
Fish. Bull. 99:443-458 (2001). 
Many fish species use estuaries of the 
southeastern United States as nurser- 
ies (e.g. Skud and Wilson, 1960; Gunter, 
1967), but coastal habitat degradation 
threatens many of the economically 
important fisheries that rely on estuar- 
ies ( Gilmore, 1995 ). The re-enacted Mag- 
nuson-Stevens Fishery Conservation 
and Management Act (MSFCMA) was 
developed to protect or enhance fish- 
eries habitats, by first requiring infor- 
mation regarding the value of coastal 
habitats to the survival of marine 
organisms (e.g. Schmitten, 1996). A 
simple approach to ranking relative 
habitat value is to compare intraspe- 
cific fish distributions with respect to 
habitat in different estuaries. Associa- 
tions between abundance and habitat 
can assist in predicting the response of 
coastal fish populations to changes in 
these habitats. Remarkably, such infor- 
mation is rarely available except for 
the most economically valuable species 
(Haedrich, 1983). 
Freshwater inflows to estuaries of 
the southeast United States have been 
severely altered in the last 150 years 
and coastal development continues to 
divert more water away from estuaries 
(Stickney, 1984). The MSFCMA’s Es- 
sential Fish Habitat mandate provides 
a policy framework for identifying the 
effects of reduced freshwater inflows 
on estuarine-dependent species. Yet re- 
searchers and managers often charac- 
terize species as estuarine-dependent 
more on intuition than rigorous exami- 
nation of data. Able and Fahay (1998) 
outlined three criteria for defining es- 
tuarine-dependence: 1) predictable use 
of estuaries, 2) non-use of suitable al- 
ternative habitats, and 3) demonstra- 
ble effect on a fish population from a 
loss of estuarine habitat. The first two 
criteria are best addressed with field 
studies, but even such simple descrip- 
tions of habitat use at a landscape level 
are lacking for most estuarine fish spe- 
cies (Hoss and Thayer, 1993). 
One example of this type of data gap 
is that for ladyfish, Elops saurus, a fish- 
ery species that inhabits coastal waters 
of Florida (Hildebrand, 1963; Murray et 
ah, 1987; FMRI 1 ). Ray (1997) listed la- 
dyfish as an estuarine-dependent spe- 
cies but little is known about its use 
of habitat in coastal waters. Ladyfish 
are probably considered to be estua- 
rine-dependent because they spawn in 
offshore waters and metamorphosing 
larvae and juveniles are found inshore 
(Hildebrand, 1943; Gehringer, 1959; El- 
dred and Lyons, 1966). However, la- 
dyfish tolerate a wide range of salini- 
ties (Alikunhi and Rao, 1951; Gunter, 
1956; Gehringer, 1959; Bayly, 1972). 
Numerous studies have reported the 
occurrence of small juveniles in ineso- 
haline or lower-salinity waters (<18 
ppt), which is consistent with an estua- 
rine-dependent life history (Tagatz and 
Dudley, 1961; Gunter and Hall, 1965; 
Zilberberg, 1966; Tagatz, 1968; Tagatz 
and Wilkens, 1973; Sekavec, 1974; Gov- 
oni and Merriner, 1978 [and references 
within]; Thompson and Deegan, 1982; 
Peterson and Ross, 1991). Moreover, 
large ladyfish are present throughout 
1 FMRI ( Florida Marine Research Institute ): 
www.floridamarine.org 
