DeVRIES and CHITTENDEN: SPAWNING TO MORTALITY OF SILVER SEATROUT 



Figure 5.— Length frequencies (moving averages of 

 three) of C. nothus captured off Freeport, Tex., 6-15 

 January 1974, by depth. Frequencies were reanalyzed 

 from Chittenden and McEachran (1976, fig. 10). Group 

 identity often is not clear where spawned groups meet. 



70 



id 



30 



110 130 150 170 



TOTAL LENGTH (mm) 



190 



210 



230 



50 



70 



90 110 130 150 



STANDARD LENGTH (mm) 



170 



190 



captured during late May, June, and late Sep- 

 tember (Fig. 6), and other females 130 mm SLor 

 larger were in the late developing stage. Some 

 males had large gonads from May through Sep- 

 tember, and running ripe males were captured 

 off Freeport in June and off Port Aransas in Sep- 

 tember. Females were only in the developing 

 and resting stages in November and December, 

 and no large females were captured from Febru- 

 ary through April. 



20 -i 



< 



o 



J 



EZZ42 



O 5 



n=23 = 



" bfEj 



n=7 



10-i 



^T" 



1 1 — I 



w Xtt^/A 



l 1 i 

 n=17 



UJ z 



2 ^ 5 - 



or. 



:1 



& 



n=24 O "1 n =2 



10 -L 



-Ft- 



rnS 



n=15 



\fl , , , r ,rv 



' 4 ' 5 1 6 1 7 



n=1 



3 4 5 6 7 8 



through July 1978, but the comparatively few in- 

 dividuals of the 1976 year class appeared only in 

 October and November (Fig. 4). 



Cynoscion nothus reached 130-190 mm SL at 

 age I. Fish of the dominant August and Septem- 

 ber spawned groups averaged 145-150 mm SL at 

 11 mo, although individuals ranged from 125 to 

 170 mm SL (Table 2). Similarly, the few survi- 

 vors of the May groups were 130-190 mm SL at 

 11-14 mo. These observed sizes at age agree with 

 the mean back-calculated length of 156 mm SL 

 presented later. 



Growth increments varied between months. 

 The August and September spawned groups 

 grew fastest in June and September, averaging 

 about 25-30 mm SL/30 d (Fig. 7). Growth of re- 

 cently hatched young steadily decreased from 

 October to December and was smallest during 

 the December-March period when increments 

 averaged 5 mm SL/30 d. Growth increments 

 then steadily increased to about 15-20 mm SL/30 

 d from March to June. The apparent pattern of 

 greatest growth during the warm months and 

 slowed growth during winter might be mislead- 

 ing. We have no growth data for the late summer 

 period when the August-September groups 



MATURITY STAGE 



Figure 6.— Monthly maturity stages of female C. nothus. Ma- 

 turity stages are 3) early developing, 4) late developing, 5) 

 gravid, 6) ripe, 7) spawning/spent, and 8) resting. 



Growth and Age Determination 

 by Length Frequency 



Only one year class of C. nothus occurred or 

 dominated in any 1 mo. Fish of the 1976 and 1977 

 year classes occurred off Port Aransas during 

 June, July, and August 1977 (Fig. 3). These were 

 the only months when two year classes were 

 clearly evident, although the comparatively few 

 large individuals of uncertain identity in Sep- 

 tember-October 1977 probably were of a second 

 year class. Only the 1976 and 1977 year classes 

 occurred off Freeport from October 1977 



40 n 



>. 



n 



o 

 co 



CO 



E20H 



E 



O 



DC 



O 



I - Sen ?7 A„g-Sep 77 modes (Pol 

 Q - Sep /Aug-Sep lower limit 

 □ - Aug-Sep 77 midranges 



V Aug Sep , modei 



V AugSep^rrudrangei 



A Aug J7 modei IPorl Aransas) 

 A - Aug 77 model (FreepcMl 

 Sep 77 '"O' 1 " ,P °" Afansasl 

 ^ - Sep . modes (Frecpon) 



Jan 

 Feb 



Feb 

 Mar 



— J— 

 Mar 

 Apr 



Apr 



May 



— 1— 

 May 

 Jun 



- 1 - 

 Jul 

 Aug 



fcug 



Spr: 



— r~ 



Sep 

 Oct 



—I 1 



Oct Nov 

 Nov Dec 



-I 

 Dec 

 Jan 



PERIOD WHEN GROWTH OCCURRED 



Figure 7.— Monthly growth increments of C. nothus. Unad- 

 justed growth increments (Table 2) were adjusted to growth/ 

 30 d. 



493 



