Schmid Marine turtle populations of the east-central coast of Florida 



149 



gerhead turtles captured on the east-central coast of 

 Florida were mid-subadults (50-70 cm), typical of 

 immature loggerhead turtles in the western Atlan- 

 tic Ocean. There was a shift to a larger size class 

 during the spring and summer, a period when repro- 

 ductively active adults immigrate to the nesting 

 beaches of southeast Florida (Henwood, 1987a). At 

 that time, some immature loggerhead turtles emi- 

 grated to foraging grounds as far north as Chesa- 

 peake Bay. Captures of adult loggerhead turtles in 

 the coastal waters of Florida declined by late sum- 

 mer with the end of the nesting season. Conversely, 

 the presence of subadult loggerhead turtles increased 

 with the onset of winter. 



Kemp's ridley turtles in the northwestern Atlan- 

 tic are transported from their natal beaches in Mexico 

 by major oceanic currents in the Gulf of Mexico (Col- 

 lard and Ogren, 1990). The smallest Kemp's ridley 

 turtles captured on the east coast of Florida coincide 

 with the minimum size class for postpelagic turtles 

 in the Gulf of Mexico (Ogren, 1989). Skeleto- 

 chronological age estimates indicate that these 

 turtles may be two years old (Zug and Kalb, 1989), 

 which may indicate the length of this species' pelagic 

 developmental stage. Recapture data from the 

 present analysis and that of Henwood and Ogren 

 ( 1987) suggest that Kemp's ridley turtles on the Atlan- 

 tic coast overwinter in the Cape Canaveral area and 

 migrate to northern foraging grounds during the sum- 

 mer. The lack of significant numbers of adult turtles in 

 the northwestern Atlantic suggests that Kemp's ridley 

 turtles migrate from the U.S. east coast upon reaching 

 sexual maturity. Recently, a Kemp's ridley turtle cap- 

 tured and tagged on the southeast coast of Florida was 

 observed nesting in the western Gulf of Mexico. 10 



Relatively low numbers of green turtles have been 

 captured in the Cape Canaveral area. This observa- 



10 Martin, E. Applied Biology, Inc., P.O. Box 974, Jensen Beach, 

 FL, 34958. Personal commun., 1994. 



tion may be the result of this species preference for a 

 habitat other than the Port Canaveral ship channel 

 and adjacent areas of shrimp trawling. Capture data 

 from fishery-independent studies indicate that early 

 subadult (20-40 cm) green turtles inhabit the 

 nearshore reef tracts off the southeast coast of Florida 

 (Ernest et al., 1989; Wershoven and Wershoven, 1989, 

 1992; Guseman and Ehrhart, 1990). A slightly larger 

 size class of green turtle was captured on the seagrass 

 shoals of the Indian River Lagoon system (Mendonca 

 and Ehrhart, 1982). Seventy-eight percent of the 108 

 green turtles captured in Mosquito Lagoon were 

 greater than 40-cm carapace length. Furthermore, 

 green turtles captured in the Indian River Lagoon, 

 south of Sebastian Inlet, were significantly larger 

 than those collected on the reefs offshore of Vero 

 Beach (Guseman and Ehrhart, 1990). 



There are a number of problems with the growth 

 data presented in this paper. Extrapolating yearly 

 growth rates from short-term recaptures amplifies 

 measurement error. Extremely large and negative 

 growth values were usually the result of short inter- 

 vals between capture and recapture. Differences in 

 the measuring techniques used by other investiga- 

 tors was a major source of error when computing 

 growth rates. Length measurements are often re- 

 ported as "straight-line carapace length" when, in 

 fact, there are four possible straight-line carapace 

 lengths: total, standard, notched, and minimum 

 (Pritchard et al., 1983). Standardized methods of 

 measurement, or a definition of the measurement 

 technique and accurate conversions between the vari- 

 ous techniques, are necessary for comparisons be- 

 tween studies (Bjorndal and Bolten, 1988). The 

 growth models presented in this analysis should be 

 interpreted cautiously given the forementioned prob- 

 lems with the database. 



In conclusion, the results of this study are indica- 

 tive of the importance of east-central Florida as a 

 developmental habitat for three species of marine 



