Sand seatrout, continued 



Physical/Chemical Characteristics : 

 Temperature: The sand seatrout is apparently sensi- 

 tive to temperature extremes, and temperature ap- 

 pears to affect distribution more than does salinity 

 (Trent et al. 1969, Vetter 1982). 



Temperature - Eggs: Eggs have been collected in 

 water temperatures from 24.5° to 29°C (Holt et al. 

 1988). 



Temperature - Larvae and Juveniles: Spawning oc- 

 curs only above 20°C, and larvae are only found at 

 these temperatures (Ditty pers. comm.). Most juve- 

 niles are found at temperatures above 1 0°C; however, 

 they have been reported from 5° to 36.9°C (Gunter 

 1945, Wang and Raney 1971, Christmas and Waller 

 1973, Warren and Sutter 1982, Cowan and Shaw 

 1988, Cowan et al. 1989). Copeland and Bechtel 

 (1974) reported optimum catches in temperatures of 

 20° to 35°C. Some have been caught in temperatures 

 as high as 40°C (Gallaway and Strawn 1974). 



Temperature - Adults: Adults prefer temperatures of 

 12° to 36°C (Miller 1964, Vetter 1977, Benson 1982) 

 (Simmons 1957). 



Salinity - Eggs: Eggs have been collected in salinities 

 from 27 to 37%o (Holt et al. 1988). 



Salinity - Larvae and Juveniles: Larvae mostly occur 

 from 14° to 21 °C in water salinities of 15 to 36%o 

 (Cowan 1985, Cowan and Shaw 1988, Cowan et al. 

 1989). Small sand seatrout have been reported in 

 salinities from to 34.5%o (Wang and Raney 1971, 

 Christmas and Waller 1973, Wagner 1973, Warren 

 and Sutter 1982). In Mississippi Sound, best catches 

 for fish with total lengths (TL) of 20 to 90 mm were 

 reported in salinities <15%°; fish of 90 to 220 mm TL 

 were caught in salinities >1 5%o at 25 to 30° C (Warren 

 and Sutter 1982). 



Salinity - Adults: Adults have been caught in salinities 

 as high as 45%o (Simmons 1957). 



Dissolved Oxygen: Sand seatrout avoid water with 

 dissolved oxygen (DO) less than 4.6 to 5.0 mg/l (Benson 

 1982). 



Movements and Migrations : Shlossman and Chittenden 

 (1 981 ) noted that the inshore movement of young sand 

 seatrout coincided with periods of rising sea level in the 

 northern Gulf of Mexico due to surface currents and 

 prevailing onshore winds. Larvae spawned in the 

 northwestern Gulf of Mexico appear to be carried 

 inshore from spawning grounds by longshore currents 

 (Cowan and Shaw 1 988). Larvae migrate into shallow 

 areas of the upper estuaries and apparently prefer 



small bayous, shallow marshes, and channels during 

 their early development (Ditty et al. 1 991 ). Larvae and 

 early juveniles (<30 mm SL) first appear in estuaries in 

 April and occur throughout the summer and early fall, 

 but with distinct peaks during April-May and Septem- 

 ber-October (Swingle 1 971 , Franks et al. 1 972, Warren 

 and Sutter 1982, Ditty et al. 1991). Catch data indi- 

 cates that they move into the low salinity waters (less 

 than 15%o). A migration from bay waters to offshore 

 breeding grounds usually occurs in late fall or winter 

 (Springer and Woodburn 1960, Warren and Sutter 

 1 982) or with a decrease in temperature (Gunter 1 938, 

 1945, Kelley 1965, Perry 1970, Wagner 1973, Vetter 

 1 977, Warren and Sutter 1 982, Vetter 1 982, Ditty et al. 

 1 991 ). Most have left the estuaries by December, but 

 some remain all winter. The sand seatrout will also 

 move to deeper water to avoid extremes in tempera- 

 ture (Vetter 1982). Adults move back into higher 

 salinity (>15%o) areas of estuaries after spawning 

 (Benson 1982). Recruitment of juveniles into estuaries 

 occurs from spring through the fall (Gunter 1945, 

 Christmas and Waller 1 973, Warren and Sutter 1 981 ). 



Reproduction 



Mode : This species has separate male and female 

 sexes (gonochoristic). Fertilization is external, by 

 broadcast of milt and roe into the water column. 



Spawning : Sand seatrout adults first spawn at age 12 

 months (Ditty et al. 1991). Spawning has been re- 

 ported from March through September (Wagner 1 973, 

 Shlossman and Chittenden 1981, Warren and Sutter 

 1982) with limited spawning possible as early as De- 

 cember (Cowan et al. 1 989) or January (Cowan 1 985, 

 Cowan and Shaw 1 988, Ditty et al. 1 991 ). Based on the 

 presence of larval sand seatrout in the northern Gulf of 

 Mexico, it can be inferred that spawning occurs Febru- 

 ary through October, with peaks in March-April and 

 July-August (Ditty 1 986, Ditty et al. 1 988). Shlossman 

 and Chittenden (1981) identified two spawning peaks 

 for sand seatrout in Texas Gulf waters. The first peak 

 occurred from early March to May (spring) and the 

 second occurred during August to September (late 

 summer). Other studies indicate a broad period of 

 spawning during spring and late summer (Franks et al. 

 1 972, Gallaway and Strawn 1 974, Moffett et al. 1 979). 

 Spawning usually occurs during the early evening 

 hours (Shipp 1986, Ditty et al. 1991). Perry (1970) 

 suggests sand seatrout spawn throughout the winter in 

 deep water (73-91 m) based on catches of females in 

 February and March with roe leaking from their anal 

 pore. Sand seatrout spawn in the higher salinity 

 estuarine and nearshore Gulf waters (Sutter and 

 Mcllwain 1987). Most spawning appears to occur in 

 the shallow Gulf primarily in waters between 7 to 1 5 m 

 in depth (Cowan 1985), but can occur in depths up to 

 91 m and as far as 175 km from shore (Perry 1970, 



254 



