FISHERY BULLETIN: VOL. 80, NO. 3 



Table 3.— Periods of time, sizes, 

 last captured off 



and ages when spawned groups of C. nothus were 

 Port Aransas and Freeport, Tex. 



they approach age I. Many females were classi- 

 fied as early developing at 100-135 mm SL(Fig. 

 2). Most of the 15 fish classified as ripe or gravid 

 were 140-170 mm SL. Age compositions and 

 sizes at age presented later indicate that C. 

 nothus mature to first spawn at 12 mo. 



Silver seatrout in the northern gulf spawn 

 from early May through late October. The collec- 

 tion of fish 45-55 mm SL in late June and 50-60 

 mm in mid-July indicates that spawning begins 

 by early May off Port Aransas (Fig. 3). Spawn- 

 ing must have continued to late October, because 

 fish 25-30 mm SL were collected from mid- 

 August through early December. It appears that 

 no spawning occurred from November through 

 March or April because we captured no fish <40 



20 



Stage 2 



n = 446 



i 1 ', 



10 



Stage 3 



2 |S 



n ^uV4VK. 



n = 155 



ia 



HStage 



li- 5 " |Stage5 



-f- 1 



,'U1 



fMUU, 



n = 46 



n = 8 



5 " lStage6 



n = 7 



J " |Staae8 



n = 3 



i 1 1 "-" — 1 1 — 



70 90 110 130 150 170 



STANDARD LENGTH (mm) 



190 



Fkuire 2. — Sizes of immature and female C. nothus in matur- 

 ity stages two through eight. Maturity stages are 2) maturing 

 virgin, 3) early developing, 4) late developing, 5) gravid, 6) 

 ripe, 7) spawning/spent, and 8) resting. No stage 7 fish were 

 caught. 



mm SL after early December, and the smallest 

 fish from February to May (Figs. 3, 4) belong to 

 groups that were hatched before November and 

 continued to grow through the winter. 



Spawning occurs in two main periods each 

 year — spring and late summer — and within each 

 year class may produce at least three intrayear 

 class cohorts or spawned groups, two of which 

 may be produced in the late summer period. This 

 is indicated by the polymodal length frequencies 

 of fish collected off both Port Aransas (Fig. 3) 

 and Freeport (Fig. 4), a pattern also evident in a 

 reanalysis of Chittenden and McEachran's 

 (1976, fig. 10) data from mid-January 1974 (Fig. 

 5). The polymodal frequencies do not reflect indi- 

 vidual year classes nor do they reflect changes in 

 size with depth. The length-frequency modes 

 represent spawned groups that can be traced 

 readily as follows: 1) The August 7 7 and Septem- 

 ber 77 groups off Freeport and Port Aransas in 

 the period September-December 1977, 2) the 

 August-September76 and August-September77 

 groups, which represent composites of the two 

 individual spawned groups, in the periods Feb- 

 ruary-July 1977 off Port Aransas, March 1978 

 off Port Aransas, and February-July 1978 off 

 Freeport, and 3) the less distinct modes which we 

 interpret as May 7 e and May77 groups in the per- 

 iods April-June and September-December 1977 

 off Port Aransas and October 1977-May 1978 off 

 Freeport. The identity of a distinct group 95-130 

 mm SL off Port Aransas in August 1977 is not 

 certain. It might have hatched in spring 1977, or 

 more probably represents survivors of the Au- 

 gust-September group. Similarly, the identity 



490 



