Sand seatrout, continued 



Sheridan et al. 1984, Cowan and Shaw 1988); 

 Shlossman (1 980) suggested spawning occurs in 1 4 to 

 40 m depths. Sheridan et al. (1984) collected the 

 following percentages of ripe and mature sand seatrout 

 in the northern Gulf: 9-17 m deep (14%); 18-36 m 

 (15%); 37-55m (24%); 56-73 m (38%); 79-91 m (21%). 

 Shlossman and Chittenden (1981) used length-fre- 

 quencies gradients to identify Texas spawning areas/ 

 depths to be from 7 to 22 m. Sheridan et al. (1984) 

 speculates that the difference between Texas and the 

 northern Gulf may be due to variations in the depths of 

 the spawning grounds. Spawning appears to take 

 place initially in midshelf to offshore waters and move 

 shoreward as the season progresses (Ditty et al. 

 1991). Spawning location is probably determined by 

 salinity and intensity of spawning by water tempera- 

 ture. 



Fecundity : Sheridan et al. (1984) estimated the mean 

 fecundity for sand seatrout (1 40 mm-278 mm SL) to be 

 1 00,990 ova with a range from 28,000 to 423,000 ova. 

 They also developed equations to estimate individual 

 fecundity. 



Growth and Development 



Egg Size and Embryonic Development : Sand seatrout 

 eggs are 0.67-0.90 mm in diameter (Holt et al. 1988, 

 Ditty and Shaw 1994). They develop oviparously and 

 hatch within one day of being fertilized (Shipp 1 986). At 

 25° to 27°C eggs begin to hatch 16 to 22 hours after 

 spawning (Holt et al. 1988). Other characteristics of 

 sand seatrout eggs have not been fully described 

 (Powles1981). 



Age and Size of Larvae : Geographical location and 

 time of the year appear to have an influence on the rate 

 of larval growth (Ditty et al. 1991). Larvae spawned 

 early in the season have faster growth than those 

 spawned in the late summer. 



Juvenile Size Range : Transformation to the juvenile 

 stage occurs at a length of 1 - 1 2 mm (Ditty and Shaw 

 1 994). Recruitment of juveniles into estuaries occurs 

 from spring through the fall (Gunter 1945, Christmas 

 and Waller 1973, Warren and Sutter 1981). Their 

 estimated growth rate is 5.8 mm/week (Warren 1981). 

 Fish spawned in the spring reach 160 to 190 mm TL 

 after six months and 220 to 280 mm after one year. 

 Those spawned in late summer range from 1 20 to 1 50 

 mm TL after 6 months, and 21 to 250 mm TL after one 

 year (Shlossman and Chittenden 1981). Monthly 

 increases in total length of sand seatrout are greatest 

 during the warm water temperatures from May to 

 October (35 mm TL/month) and slowest in winter (5-10 

 mm TL/month) when waters are cooler (Shlossman 

 and Chittenden 1 981 ). Growth rates in the central and 

 eastern Gulf range from 9.3 to 27.7 mm SL/month, and 



5-10 to 35 mm TL/month in the western Gulf. 



Age and Size of Adults : In one study, the smallest 

 maturing male was 129 mm SL and the smallest 

 maturing female was 140 mm SL (Sheridan et al. 

 1 984). Sand seatrout generally mature at 1 40-1 80 mm 

 total length (TL) as they approach age I in the Gulf 

 waters of Texas (Shlossman and Chittenden 1981). 

 Maximum life span for this species is estimated to be 3 

 years, with maximum lengths of 590 mm TL reported 

 by Trent and Pristas (1977). Few sand seatrout 

 exceed a maximum of 300 mm TL although trawl- 

 caught fish up to about 500 mm TL have been reported 

 (Ditty etal. 1991). 



Food and Feeding 



Trophic Mode : The sand seatrout is a generalized 

 predator that feeds primarily in daylight hours on live 

 and dead organisms (Vetter 1977). Its food habits 

 show that it is an opportunistic carnivore whose diet 

 changes with age (Ditty et al. 1 991 ). 



Food Items : Age, habitat, abundance of suitable prey 

 and its availability in different geographic locations 

 influences the diet of the sand seatrout (Ditty et al. 

 1991). Mysids and calanoid copepods are the main 

 diet items of sand seatrout less than 40 mm SL (Sheridan 



1979, Sheridan and Livingston 1979, Levine 1980). 

 Fish are the predominant food item of all larger sand 

 seatrout, with the bay anchovy being the most fre- 

 quently consumed prey (Moffet et al. 1979, Levine 



1980, Overstreet and Heard 1982, Sheridan et al. 

 1984). Mysidaceans were eaten more often in lower 

 salinity areas, whereas fish were heavily consumed 

 near passes of the estuaries. Sand seatrout from 45 to 

 159 mm SL in Texas were found to have stomach 

 contents of 38% crustaceans, and 30% fish (Moffett et 

 al. 1979). Sand seatrout from 160 to 375 mm SL in 

 Texas contained 46% fish (mostly bay anchovies), 1 0% 

 crustaceans, and 1 % polychaetes. Sand seatrout from 

 Mississippi Sound had 3% stomatopods, 53% penaeid 

 shrimp, 7% caridean shrimp, and 55% fish (mostly bay 

 anchovies and Gulf menhaden) (Overstreet and Heard 

 1982) Fish from Lake Pontchartrain, Louisiana had 

 95% crustaceans, 4.7% fish, and a small percentage of 

 molluscs (Levine 1980). Other studies have found 

 intraspecific cannibalism and a seasonal shift in food 

 habits with more crustaceans consumed during the fall 

 and winter than during other months (Ditty et al. 1 991 ). 

 In addition, piscine prey is more abundant in the diet of 

 sand seatrout inshore than those offshore (Ditty et al. 

 1991). 



Biological Interactions 



Predation : Although predator information on this spe- 

 cies is unavailable, it seems likely that larvae and 

 juveniles may serve as minor prey items for other 



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