SHLOSSMAN and CHITTENDEN: REPRODUCTION OF SAND SEATROUT 



differences in spawning, and as noted shortly, the 

 unusual flooding near Galveston Bay during 

 spring 1979 and current transport phenomena 

 which are strongly wind-driven in the gulf and its 

 estuaries. Under nonflood conditions a single gra- 

 dient of increasing size extended from the upper 

 estuary out to at least 22 m in the gulf (Figure 9A), 

 which suggests that the dichotomous condition in 

 May- August 1979 (Figure 9B) was an exception 

 caused by flooding. 



Our data suggest that C. arenarius spawns in 

 the shallow inshore gulf, but the extent of its 

 spawning grounds is not yet clear and could vary 

 seasonally. Other workers also have reported evi- 

 dence of gulf spawning ( Gunter 1945; Moffett et al. 

 1979). Perry (1970) and Franks et al. (1972) cap- 

 tured running ripe C. arenarius in the gulf during 

 February and March at 73-91 m (about 105 km 

 offshore) which could indicate spawning offshore 

 in deep water; but the distance these fish traveled 

 before spawning is not clear. Reid (1955), Hoese 

 (1965), and Copeland and Bechtel (1974) reported 

 spawning in estuaries, but they presented little 

 evidence. However, Harmic (1958) found that the 

 closely related C. regalis spawned within Dela- 

 ware Bay. 



Clear delineation of the spawning grounds re- 

 quires understanding how this species passes from 

 spawning grounds to nurseries. The spring and 

 late summer spawning periods of C. arenarius 

 coincide with periods of rising sea level in the 

 northern gulf in response to prevailing onshore 

 winds and surface currents (Collier and 

 Hedgpeth 1950; Marmer 1954). Spawning proba- 

 bly is timed to take advantage of this seasonal 

 phenomenon to transport eggs and/or larvae from 

 inshore gulf spawning grounds to estuarine and 

 gulf nurseries as our size composition data indi- 

 cate. The bayward movement of postlarvae that 

 Simmons and Hoese (1959) reported on incoming 

 tides could be enhanced by rising sea levels and 

 prevailing onshore wmds and currents. However, 

 spawning also coincides with seasonal rainfall 

 peaks (Collier and Hedgpeth 1950) which could 

 modify estuarine transport phenomena. Currents 

 and tides in the nearshore northern gulf and its 

 shallow estuaries are influenced greatly by wind 

 and flooding (Collier and Hedgpeth 1950; Smith 

 1975). Therefore, spawned group strength of C. 

 arenarius and its spatial distribution may be in- 

 fluenced greatly by short-term wind and rainfall 

 patterns that affect current transport and, 

 thereby, survival of the eggs and/or larvae as Nel- 



son et al. (1977) reported for Atlantic menhaden, 

 Brevoortia tyr annus. 



NURSERIES AND LATER MOVEMENTS 

 Results 



Spring and late summer spawned groups use 

 both estuarine and inshore gulf nurseries in their 

 early life, although estuaries may be most impor- 

 tant for late summer fish. Recently hatched spring 

 fish were abundant in 1977-79 from May through 

 July in the inshore gulf, in Galveston Bay, and 

 Cedar Bayou (Figures 4-7). Few recently hatched 

 late summer fish were in the inshore gulf in 

 September-November of 1977-78 ( Figures 4, 5), but 

 they were common then in Galveston Bay and 

 Cedar Bayou (Figures 6, 7) and were abundant in 

 the gulf in December (Figures 4, 5). 



The main nursery of C. arenarius in the north- 

 western gulf lies in water <18 m. Fish >160 mm 

 TL occurred throughout the 4.5-46 m depth range 

 (Figure 9A). However, fish <160 mm TL only oc- 

 curred in <18 m except in May-August 1979 when 

 recently hatched spring 1979 fish were abundant 

 to 27 m and present to 37 m (Figure 9B). The Gulf 

 nursery probably expands or contracts depending 

 on spawned group strength and factors that de- 

 termine dispersal of the young. For example, the 

 great abundance of small fish in the gulf during 

 May-August 1979 might be due to increased 

 spawned group strength and/or heavy flooding in 

 the Galveston Bay area in that spring (Barris 

 1979). 



Fish that use estuarine nurseries in their early 

 life enter the gulf during mid and late fall to over- 

 winter. Spring fish grew in the gulf from May 

 through September- October 1977 and 1978 (Fig- 

 ures 4, 5), but thereafter showed no growth or 

 decreased sizes through December. This pattern 

 indicates movement from estuaries to the gulf 

 with the larger fish preceding smaller ones, as- 

 suming continued gi-ovd;h in that period. Many 

 recently hatched late summer fish entered the gulf 

 during December 1977 and 1978 (Figures 4, 5), 

 because few were in the gulf before then. Few were 

 in Galveston Bay or Cedar Bayou from December 

 through March (Figures 6, 7), although they were 

 abundant in the gulf. 



Late summer spawned groups return to es- 

 tuaries during midspring after overwintering in 

 the gulf. Although abundant in the gulf in the 

 February-April periods of 1977-79 (Figures 4, 5), 



657 



