FISHERY BULLETIN: VOL 79, NO. 4 



few late summer fish were in tiie gulf in the fol- 

 lowing May-July period except in 1977 off Port 

 Aransas. Most must have returned to estuaries in 

 midspring and remained there until they returned 

 to the gulf to spawn in August (Figure 4). Late 

 summer fish were captured in Galveston Bay in 

 May -July (Figure 6), but not in large numbers 

 which may reflect a habitat change by these larger 

 fish or avoidance of the small trawls used there. 

 Sizes of the late summer fish in the gulf remained 

 stable or decreased in July-August 1978 and 1979 

 (Figure 4). This is similar to the pattern noted in 

 the fall for spring spawned fish and suggests a 

 similar gradual dispersal of the late summer 

 groups to the gulf. 



Movements of spring spawned groups as they 

 reach age I are not clear. We captured few age I fish 

 in the spring or following summer except in March 

 and April 1979 in the gulf (Figure 4). Most appar- 

 ently die after spavniing, but our data do not 

 clarify movements of the survivors. 



Cynoscion arenarius exhibits little diel varia- 

 tion in size composition. The two spawned groups 

 off Freeport during December 1978 and in April, 

 June, and July 1979 showed little day-night size 

 variation (Figure 4). Some differences — e.g., De- 

 cember 1978 — probably reflect growth or move- 

 ments in the 2-wk period between collections. 



Discussion 



Our findings on the nurseries and later move- 

 ments of C. arenarius agree with the limited liter- 

 ature, although the complex life history of this 

 species has not been recognized. The fact that the 

 young occur in both estuaries and the inshore gulf 

 has been reported (Gunter 1945; Miller 1965; 

 Christmas and Waller 1973 ), but these workers did 

 not recognize separate spring and late summer 

 spawned groups nor possible differences in their 

 nurseries. Our finding that C. arenarius move in 

 fall from estuaries to overwinter in the gulf has 

 been reported by many workers including Gunter 

 (1938, 1945), Chambers and Sparks (1959), Perret 

 and Caillouet (1974), and Ogren and Brusher 

 (1977) who based their findings only on apparent 

 change in abundance without recognizing size 

 composition changes, or the differences between 

 spring and late summer spawned groups. Move- 

 ment of "mature" C arenarius in the period 

 April-May from the gulf to estuaries has been re- 

 ported (Simmons 1950-51 cited in Guest and 

 Gunter 1958; Simmons and Hoese 1959). These 



might have been late summer fish in agreement 

 with our findings, but these workers did not recog- 

 nize different spawned groups. Data of Perret and 

 Caillouet (1974, fig. 6), however, show return of 

 late summer fish to Vermillion Bay, La., in April 

 and May. The absence of diel size variation in C. 

 arenarius contrasts with its presence in C. nothus 

 (DeVries and Chittenden footnote 6). 



GROWTH AND AGE DETERMINATION 

 BY LENGTH FREQUENCY 



Results 



No more than two year classes of C. arenarius 

 occurred in any 1 mo in the gulf, in Galveston Bay, 

 or in Cedar Bayou (Figures 4-7). Only one year 

 class was captured from February through April, 

 except possibly in March 1979 off Freeport. Two 

 year classes usually were present in the gulf and in 

 Galveston Bay from May through December — but 

 no more than three spawned groups. 



Cynoscion arenarius averages 210-280 mm TL 

 at age I depending on spawned group. Spring fish 

 averaged 160-190 mm TL at 6 mo and 220-280 mm 

 at age I (Figure 10), although many were 200 mm 

 or more at 6 mo and some were 300 mm at age I 

 (Shlossman 1980, tables 1, 2). Late summer fish 

 were slightly smaller, averaging 120-150 mm TL at 

 6 mo and 210-250 mm at age I (Figure 10), al- 

 though many were 175 mm or more at 6 mo and 

 some were 300 mm at age I (Shlossman 1980, ta- 

 bles 1, 2). Mean sizes predicted by regression (Fig- 

 ure 10) were 250 mm TL at age L 425 mm at age II, 

 and 574 mm at age III for late summer fish. Predic- 

 tions for spring fish were 260 mm TL at age I, 301 

 mm at age II, and 160 mm at age III. Predictions 

 for spring fish are unrealistic at age III and proba- 

 bly too low at age II, because the simple polyno- 

 mial regression used describes growth as a 

 parabola. 



Growth generally was greatest in warmer 

 months and least in colder months. Both spring 

 and late summer spawned fish grew slowest (5-10 

 mm TL/30 d) in winter (Figure 11). Spring fish 

 grew fastest (35 mm TL/30 d) from May through 

 October; much variation occurred, however, and 

 zero increments in summer and mid to late fall 

 reflect movement of larger fish from estuaries to 

 the gulf, not lack of growi:h. Late summer fish 

 grew rapidly in spring; decreased increments in 

 late spring and early summer may reflect move- 

 ment of larger fish from estuaries to the gulf. 



658 



