Murphy and Taylor: Sciaenops ocellatus in Florida waters 



535 



Simmons and Breuer 1962, Yokel 1966, Jannke 1971, 

 Holt et al. 1985). Our data suggest that spawning may 

 also occur over the nearshore continental shelf and in 

 estuaries. Collections of mature or recently spent fish 

 made in nearshore Gulf waters from just outside the 

 barrier islands to depths of 69.5 m suggest that spawn- 

 ing takes place offshore in the Gulf of Mexico (Christ- 

 mas and Waller 1973; Heffernan 1977; W.A. Fable, 

 NMFS Panama City Lab., Drum seine observers trip 

 report, 18-21 Aug.'l982. Memo OO.Sep.82*002148 to 

 A.C. Jones, NMFS Miami Lab., 4 p.). Peters and 

 McMichael (1987) reported that although most spawn- 

 ing in Tampa Bay occurred close to its mouth, some 

 spawning probably took place in nearshore Gulf waters. 

 Recent egg collections provide evidence that red drum 

 spawn within Mosquito Lagoon (Johnson and Funicelli 

 In press). Our collection of females in Mosquito Lagoon 

 containing POF corroborate these findings and suggest 

 that red drum found equally far within Tampa Bay may 

 also be spawning within the estuary. Moreover, red 

 drum movement was observed during a sonic tracking 

 study in Mosquito Lagoon (Carr and Smith 1977, Carr 

 and Chaney 1976) and little directed movement dur- 

 ing the spawning season was noted. 



Age determination and growth 



Ages of red drum from to at least 18 could accurate- 

 ly be determined using otoliths. Red drum sagittae 

 showed clearly delineated, easily interpreted (100% 

 agreement between counts) hyaline and opaque bands. 

 Otoliths with 0-33 opaque bands were examined; they 

 were taken from 1085 red drum (551 Gulf coast and 

 534 Atlantic coast) with size ranges of 225-1110 mm. 

 Although ages of red drum were validated for only the 

 first 18 years, we assumed, for age and growth anal- 

 ysis, that each opaque band represents an annual mark 

 (annulus). 



Minimally overlapping monthly length frequencies, 

 a consistent marginal increment minima each year, and 

 observations of oxytetracycline-injected fish supported 

 the hypothesis that the opaque bands are annuli. Modal 

 length progressions representing the 1978, 1979, 1980, 

 and 1981 year-classes on the Gulf coast and 1980 and 

 1981 year-classes on the Atlantic coast could be fol- 

 lowed in length frequencies (Figs. 2, 3). These length 

 modes could be followed for fish up to 3 years-old and 

 consistently agreed with lengths of fish having cor- 

 responding otolith-determined ages. The periodicity of 

 the mean monthly marginal increment minima each 

 winter (December-March) for fish having one or two 

 opaque bands further suggests that opaque bands were 

 deposited annually (Fig. 4). Opaque bands on fish older 

 than age 3 are also probably annuli. Four adult red 

 drum that were injected and held in outdoor ponds for 



O 



UJ 



a. 50 



1980,1 '77^ 1976.3 



198^1,0^!^°' Aa"" 



979,2 



' , ^ ' , AUG s; 



T' ' ■■' = 309 



':^°.93o,,/r' 



SEP B2 

 1979.3 f^ " '33 



IPSO.lT^ 1978,3 



1 980 1 A 



1980.2 



979.3 

 ■^? 



19797 



,.^'C>i ..." 



200 400 600 800 1000 1200 200 dOO 600 800 1000 1200 



FORK LENGTH (mm) 



Figure 2 



Monthly length frequencies fur red drum from the Gulf coast of 

 Florida. No collections were made in April 1982. Horizontal bars show- 

 length ranges for otolith-aged year-classes and are labeled for year- 

 class and age in years. 



19 months deposited one opaque band each between 

 release (August 1986) and recapture (March 1988). 

 These fish were 5, 12, 16, and 18 years-old when 

 recaptured. 



Otoliths have been used to determine the age of red 

 drum (Miles 1951, Rohr 1964, Theiling and Loyacano 

 1976), but the use of opaque bands as an age deter- 

 minant has never been adequately tested. Off Mis- 

 sissippi, annuli apparently form on otoliths during 

 winter or spring (Rohr 1964). In Texas, where the valid- 

 ity of using scales to determine ages of red drum <4.5 

 years-old has been established (Matlock et al. 1987), 

 annuli form on scales between February and April in 



