28 
Carter R. Gilbert 
secondary or peripheral (i.e., salt-tolerant) freshwater families, exhibit a 
gradient in terms of their occurrence in fresh water. Some, such as 
Labidesthes sicculus , Fundulus chrysotus, Fundulus cingulatus , Fundu- 
lus escambiae and Fundulus lineolatus, seldom enter brackish waters. 
Others, including Poecilia latipinna , Lucania parva , Rivulus marmora- 
tus and Menidia beryllina, often are found there. Finally, species such 
as Alosa alabamae, Alosa chrysochloris, Acipenser oxyrhynchus , Aci- 
penser brevirostrum and Morone saxatilis are anadromous and regu- 
larly enter fresh water to spawn. 
The area south of the Suwannee and St. Johns river drainages con- 
tains only about 50 of the 72 species analyzed, and represents still 
further impoverishment. Despite this, the fishes of peninsular Florida 
show a high percentage of endemism, as is true also of many plants and 
other animals (Neill 1957). Species such as Micropterus salmoides, 
Lepomis macrochirus, Notropis emiliae and probably Lepomis margi- 
natus have distinctive subspecies restricted to peninsular Florida (Bailey 
and Hubbs 1949; Felley 1980; Gilbert and Bailey 1972; Bruce H. Bauer, 
pers. comm.), and for species such as Ictalurus natalis there is clearcut 
differentiation at the racial level (Lodge 1974). 
The south Georgia-peninsular Florida area is notable for the paucity 
of species in three fish families that otherwise are dominant through- 
out eastern North America: Cyprinidae (13 species), Percidae (5 species) 
and Catostomidae (2 species). By comparison, there are 47, 34 and 13 
species in each of these respective groups in the faunistically richer 
Mobile Bay basin. The families Centrarchidae, Ictaluridae (primary- 
division groups) and Cyprinodontidae (a secondary-division group), 
along with the large number of marine forms, provide outstanding con- 
tributions to the fauna in terms of numbers of species. A total of 17 
centrarchid, 8 ictalurid and 1 1 cyprinodontid species occur in southern 
Georgia and peninsular Florida, as compared with 16, 12 and 8, respec- 
tively, for these groups in the Mobile Bay basin. The total of 17 repre- 
sents exactly half the total number of described centrarchid species found 
in eastern North America. The 8 ictalurids equal about one-fifth the 
total number of species in eastern North America, and the 11 cyprino- 
dontids represent about one-third of the freshwater members of this 
family from the Mississippi basin eastward. 
In summary, the south Georgia-peninsular Florida area may be 
characterized by (a) a comparative paucity of species in the families 
Cyprinidae, Percidae and Catostomidae; (b) an “average” number of 
species of Ictaluridae; (c) a comparatively large number of species of 
Centrarchidae and Cyprinodontidae; and (d) an unusually large number 
of marine species that invade fresh waters on a regular or casual basis. 
