SHLOSSMAN and CHITTENDEN: REPRODUCTION OF SAND SEATROUT 



because few fish 25-60 mm TL were captured from 

 late June through August in the gulf (Figures 4, 

 5), in Galveston Bay (Figure 6), or at Cedar Bayou 

 (Figure 7). 



Discussion 



Our findings on C. arenarius spawning agree 

 with the limited literature. The small size at 

 maturity agrees with Gunter's (1945) capture of a 

 ripe male only 157 mm TL. The broad March- 

 September spawning period found agrees with 

 many studies, including Franks et al. (1972), Gal- 

 laway and Strawn ( 1974 ), and Moffett et al. ( 1979). 

 The fact that spawning occurs in distinct spring 

 and late summer peaks has not been recognized 

 clearly but is supported by: 1) the midsummer lull 

 in spawning that Margraf ( 1978) noted; 2) the late 

 winter-early spring and early fall spawnings that 

 Juneau (1975) observed; and 3) the distinct modes, 

 one formed in spring and one formed in late sum- 

 mer, in size data of Gunter (1945:76), Christmas 

 and Waller (1973, fig. 8), Gallaway and Strawn 

 (1974, table 24), Swingle and Bland (1974:41), 

 Moffett (1975, fig. 19), and Landry (1977, fig. 23, 

 24). Multiple spawning peaks also have been re- 

 ported for other Cynoscion spp. such as C. nothus 

 (DeVries and Chittenden^) and C. regalis (Daiber 

 1957 and Harmic 1958 cited in Thomas 1971; 

 Massmann et al. 1958; Merriner 1976). 



SPAWNING AREAS, EARLY 

 NURSEIUES, AND MOVEMENTS 



Results 



Sand seatrout of both spring and late summer 

 groups spawn in the inshore gulf. Spawning and 

 nursery areas of spring spawned groups are indi- 

 cated by distinct size gradients in length frequen- 

 cies for May-August 1979 (Figure 9B): 1) an es- 

 tuarine gradient in which the smallest fish were in 

 the upper estuary at Cedar Bayou while larger 

 ones were in Galveston Bay and at 4.5 m in the 

 gulf, 2) a gradient in the gulf in which the smallest 

 fish were at 7-15 m and sizes increased in deeper 

 water, and 3) another gradient in the gulf in which 

 the smallest fish were at 7-15 m but sizes increased 

 in shallower water. Length frequencies from 

 Cedar Bayou, Galveston Bay, and the gulf off 



''DeVries, D. A., and M. E. Chittenden,. Jr. In prep. Spawn- 

 ing, age determination, and population dynamics of the silver 

 seatrout, Cynoscion nothus, in the Gulf of Mexico. 



Freeport indicate growth continued in May- 

 August 1979 (Figures 4, 6, 7). Therefore, the first 

 size gradient indicates dispersion of larger 

 juveniles down the estuary The latter two size 

 gradients indicate outward dispersion of larger 

 young and/or eggs and larvae from spawning 

 grounds near 7-15 m in the gulf to deeper and 

 shallower water. Late summer spavraed groups 

 also use inshore gulf spawning grounds as indi- 

 cated by locations of mature fish at spawning time. 

 Capture locations of mature and ripe adults at 

 spawning time also suggest an inshore gulf 

 spawning area. Many fish of the late summer 1978 

 group reached age I and entered the gulf in August 

 1979 (Figure 4), presumably to spawn near the 

 7-22 m depths where they were captured; none 

 were captured at 4.5 or 55-100 m (Chittenden un- 

 publ. data), but the 27-46 m depth range was not 

 occupied in that cruise. Five ripe stage fish were 

 captured in April and May 1978 at 14-46 m in the 

 gulf. However, it is not clear how far these fish 

 traveled before spawning. 



Discussion 



The estuarine size gradient that we found could 

 reflect spawning grounds in the upper estuary, or 

 most probably, spawning grounds that encompass 

 the inshore gulf and/or lower estuary. This gra- 

 dient probably does not reflect an upper estuarine 

 spawning ground, because the early life history of 

 C. arenarius is much like that of the Atlantic 

 croaker, Micropogonias undulatus. The Atlantic 

 croaker exhibits egg and/or larval transport to the 

 upper estuary from spawning grounds in the sea 

 (Wallace 1940; Haven 1957) and well-documented 

 estuarine size gradients (Gunter 1945; Haven 

 1957; Reid and Hoese 1958). Moreover, a similar 

 early life history has been suggested for other 

 Sciaenidae, especially C. regalis (many references 

 in Wilk 1979). 



Our explanation for the estuarine size gradient 

 conflicts with the size pattern in the gulf The 

 latter pattern suggests outward dispersal of young 

 and/or transport of eggs and larvae from spawn- 

 ing grounds near 7-15 m. The direction of move- 

 ment suggested by the estuarine gradient, how- 

 ever, is opposed to the direction of movement 

 suggested by the gulf gradient in which sizes in- 

 crease inshore. We offer no simple explanation for 

 the apparent dichotomy except that it might 

 reflect: possibly separate estuarine and gulf 

 spawning grounds which might involve temporal 



655 



