Spotted seatrout, continued 



mas 1979). 



Turbidity: Spotted seatrout appear to prefer areas of 

 low turbidity (Pearson 1 929). Increased mortality due 

 to hurricane-induced high turbidity levels has been 

 reported from Louisiana (Perret et al. 1980). 



Movements and Migrations : In Alabama, early juve- 

 niles move into tidal rivers in late fall to overwinter (Van 

 Hoose 1987). Adult seatrout migrate very little with 

 most movements occurring seasonally in association 

 with thermal and salinity tolerances, and with spawning 

 activities (Tabb 1966, Bryant et al. 1989, Helser et al. 

 1993). Large individuals often seek cooler deeper 

 water during the summer, and deeper, warmer waters 

 of bays or the nearshore Gulf of Mexico during the 

 winter (Pearson 1929, Gunter 1945). Several studies 

 indicate that spotted seatrout are estuary-specific, 

 particularly in Florida, with very little movement occur- 

 ring between estuaries (Killam et al. 1992). This is 

 further substantiated by the existence of independent 

 populations of this species in different estuaries (Iversen 

 and Tabb 1962, Weinstein and Yerger 1976). In 

 Texas, although evidence suggests that sub-popula- 

 tions in bay systems mingle very little, mixing of differ- 

 ent groups may occur during the spawning season 

 which may be the reason for the low degree of variabil- 

 ity between major bays in this state (King and Pate 

 1992, Baker and Matlock 1993). 



Reproduction 



Mode : Spotted seatrout have separate male and fe- 

 male sexes (gonochoristic). Fertilization is external, by 

 broadcast of milt and roe into the water column, and 

 development is oviparous. 



Spawning : Sound produced by specialized muscles 

 inserted at the swim bladder wall may have a purpose 

 in spawning activities (Mok and Gilmore 1983). The 

 spawning season is protracted and varies throughout 

 the Gulf of Mexico. It can begin as early as February 

 and continue until October (Pearson 1929, Gunter 

 1945, Herke et al. 1984, Van Hoose 1987, McMichael 

 and Peters 1989), but generally runs from March to 

 October (Hein and Shepard 1 980). Saucier and Baltz 

 (1 993) reported that spotted seatrout form "drumming" 

 aggregations in estuarine waters of Louisiana from 

 late May to early October, at salinities from 7to 27%o, 

 and temperatures from 24.5 to 33.5°C, from 6pm to 

 midnight, and that spawning sites were primarily lo- 

 cated in deep, moving water in passes between barrier 

 islands. Based on the presence of larval spotted 

 seatrout in the northern Gulf of Mexico, it can be 

 inferred that spawning occurs February through Octo- 

 ber, with a peak from April through August (Ditty et al. 

 1988). Spawning may occur throughout the year in 

 southern Florida and Mexican waters (Tabb 1961, 



Tabb and Manning 1961, NOAA 1985). Spawning 

 occurs at dusk with the peak activity periods usually in 

 late April-June and August-September, and is prob- 

 ably related to water temperature and increasing or 

 decreasing photoperiods (Tabb and Manning 1961, 

 Hein and Shepard 1980, Perret et al. 1980, Wade 

 1981, Van Hoose 1987, Brown-Peterson et al. 1988, 

 McMichael and Peters 1989, Chester and Thayer 

 1 990). The recorded temperature range for spawning 

 is 24 to 30°C, with 23°C suggested as the minimum 

 temperature forsuccessful spawning (Brown-Peterson 

 et al. 1988). A Florida study recorded surface water 

 temperatures of 1 5.5 to 31 °C during spawning months 

 (McMichael and Peters 1989). In Florida, spawning is 

 essentially completed by the time temperatures rise to 

 28.3°C (Tabb 1966, Johnson 1978). Spawning prob- 

 ably occurs in moderate to high salinities (Powell et al. 

 1989). The surface salinity during spawning months 

 can range from 18.5 to 36% (McMichael and Peters 

 1989), and peak spawning occurs between 30 and 

 35% (Tabb 1966). No spawning has been observed 

 above 45%o (Simmons 1 957). Spawning occurs prima- 

 rily within coastal bays, estuaries, and lagoons, usually 

 in shallow grassy areas, or near passes, and in deeper 

 holes or channels with the eggs drifting into the grassy 

 areas (Welsh and Breder 1923, Pearson 1929, Guest 

 and Gunter 1958, Tabb 1966, Etzold and Christmas 

 1979, Mok and Gilmore 1983, McMichael and Peters 

 1989, Powell et al. 1989, Chester and Thayer 1990). 

 Spawning probably occurs in water that is 3 to 4.6 m 

 deep. Spawning may also occur in tidal passes, areas 

 of little or no vegetation, and, in Louisiana, the higher 

 salinity waters of lower bays and the nearshore Gulf of 

 Mexico (Sabins and Truesdale 1974, Allshouse 1983, 

 Herke et al. 1 984, Helser et al. 1 993). 



Fecundity : Spotted seatrout are multiple spawners and 

 their fecundity is difficult to estimate (Brown-Peterson 

 et al. 1 988). Estimates of fecundity range from a mean 

 of 14,000 from 283 mmTL l-year class females to 1.1 

 million eggs for IV-year class averaging 504 mm TL 

 (Sundararaj and Suttkus 1962). Recent evidence 

 suggests that these fecundity estimates may be low 

 and that actual annual fecundity may average greater 

 than 10 million eggs. Spawning frequency appears to 

 be high and is estimated to occur every 3.6 days, but 

 this frequency is probably not sustained throughout the 

 entire spawning season (Brown-Peterson et al. 1 988). 



Growth and Development 



Egg Size and Embryonic Development : Eggs are spheri- 

 cal, usually with one oil droplet. Their diameter ranges 

 from 0.7 to 0.85 mm, and hatching occurs 16 to 20 

 hours after fertilization at 25°C (Fable et al. 1978). 

 Incubation times of 21 hours at 23°C and 15 hours at 

 27°C have also been reported (Ditty and Shaw 1994). 



262 



