612 



Abstract.— During 1986-91, we exam- 

 ined 2088 common snook, Centropomus 

 undecimaHs. captured in Jupiter and 

 Lake Worth inlets and adjacent waters 

 on the east coast of Florida and 1784 

 common snook captured in Tampa Bay 

 on the west coast of Florida. Offish that 

 were sexed, females ranged in length 

 from 397 to 1105 mm FL, and males 

 ranged from 124 to 925 mm FL. East 

 coast fish were larger overall than west 

 coast fish. Age of common snook was 

 determined from sectioned otoliths. 

 Results from the return of 80 oxytetra- 

 cycline-marked otoliths combined with 

 analyses of monthly patterns in mar- 

 ginal increments and the percentage of 

 otoliths with an annulus on the edge, 

 demonstrated that a single annulus is 

 formed each year. Common snook can 

 hve to 21 years, but most of the fish 

 in our sample were from 1 to 7 years 

 old. The von Bertalanffy growth models 

 were significantly different iP<0.001) 

 for each coast and suggested that east 

 coast snook grow faster than west coast 

 snook. Common snook are protandric 

 hermaphrodites. The gonads of 27 

 transitional specimens contained both 

 degenerating spermatogenic and devel- 

 oping ovarian tissue, and sex reversal 

 was observed in captive common snook. 

 Common snook sex ratios and length- 

 frequency distributions were also con- 

 sistent with a diagnosis of protandric 

 hermaphroditism. Females smaller 

 than 500 mm FL were uncommon, and 

 only one female less than 400 mm long 

 was captured. The predicted lengths 

 and ages at which 50'* of the fish in the 

 population would be females were 767 

 mm FL and 7.4 years for the east coast 

 and 608 mm FL and 5.1 years for the 

 west coast. Some males on both coasts 

 were sexually mature at lengths less 

 than 200 mm FL and at age 0; most 

 age- 1 males were mature on both coasts. 

 All females were considered mature 

 because they were derived from post- 

 spawning males. 



Age, growth, maturation, and 

 protandric sex reversal in common snook, 

 Centropomus undecimalis, from the 

 east and west coasts of South Florida 



Ronald G. Taylor 



Florida Fish and Wildlife Conservation Commission 



Florida Marine Research Institute 



100 Eighth Avenue SE 



St. Petersburg, Florida 33701-5095 



E-mail address: ron.taylor^fwc state.fl.us 



James A. Whittington 



Flonda Fish and Wildlife Conservation Commission 

 Tequesta Field Laboratory 

 Florida Manne Research Institute 

 19100 SE Federal Highway 

 Tequesta, Flonda 33469 



Harry J. Grier 



Florida Fish and Wildlife Conservation Commission 



Stock Enhancement Research Facility 



Florida Manne Research Institute 



14495 Harllee Road 



Port Manatee, Flonda 34221 



Roy E. Crabtree 



National Marine Fishenes Service, F/SER23 

 9721 Executive Center Drive North 

 St Petersburg, Flonda 33702 



Manuscript accepted 6 January 2000. 

 Fi.sh. Bull. 98:612-624 (20(J0I. ' 



Common snook, Centropomus undec- 

 imalis, (Perciformes: Centropomidae) 

 are valuable euryhaline fishes that 

 inhabit tropical and subtropical estua- 

 rine systems of the western Atlantic. 

 They are abundant off the east coast 

 of Florida from Cape Canaveral south- 

 ward around the peninsula to Cedar 

 Key off the west coast. They also inhabit 

 waters off Galveston, Texas, south to 

 Rio de Janeiro, Brazil (Gilmore et al., 

 1983; Rivas, 1986). They are commer- 

 cially exploited throughout most of their 

 range, except in Texas and Florida 

 where they traditionally have supported 

 large recreational fisheries (Matlock 

 and Osburn, 1987). Snook are steno- 

 thermic: their northern range is limited 

 by the winter 15"C isotherm (Shafland 

 and Foote. 1983), similar to the dis- 



tribution of mangroves which is their 

 principal habitat ( Marshall, 1958; Gilm- 

 ore et al., 1983). Genetic studies of the 

 stock structure suggest that in Florida, 

 east coast and west coast populations 

 are separate stocks (Tringali and Bert, 

 1996). 



Anglers target common snook because 

 of their fighting ability and culinary 

 value (Tucker et al., 1985; Matlock and 

 Osburn, 1987 ), and concerns about over- 

 fishing have resulted in a long history 

 of regulation of the fishery off Florida 

 (Bruger and Haddad, 1986). Size limits 

 were first imposed on the fishery in 

 1953, and the sale of common snook in 

 Florida has been prohibited since 1956. 

 In 1994, a management goal was estab- 

 lished to maintain a minimum spawn- 

 ing potential ratio (SPR) of 40^/ for 



