GE0GHEGAN and CHITTENDEN: REPRODUCTION. MOVEMENTS OF LONGSI'INE I'OKGY 



with greatest spawning in June (Bigelow and 

 Schroeder 1953; Finkelstein 1969a). 



10 



12 



9 

 6 

 3-I 



Immature 

 n = 604 



Maturing Virgin 

 n = 150 



Early Developing 

 n=142 



TOTAL LENGTH (mm) 



Figure 7.— Length frequency (moving averages of three) of 

 Stenotomus caprinus captured in the north central Gulf aboard 

 the Oregon II, 10 April-1 May 1980. Probable ages and year 

 class identities are indicated. 



MOVEMENTS, SPAWNING AREAS, 

 AND DIEL VARIATION IN CATCH 



Results 



10 



5- 



40 



30- 



20- 



10 



Ripe 

 n = 152 



J V SM ^.- 



Spent/Resting 

 n = 572 



40 80 120 160 



TOTAL LENGTH (mm) 



Figure 6.— Length frequencies (moving averages of three) of 

 immature and female Stenotomus caprinus by maturity stages. 

 See Table 1 for definitions of maturity stages. Brackets indi- 

 cate size ranges used to calculate the mean length of fish ap- 

 proaching age I for each maturity stage. 



Stenotomus caprinus exhibit size and age gra- 

 dients with depth related to their movements, 

 spawning areas, and recruitment. Although cap- 

 tured from 18 m to 100 m (Fig. 9), they were most 

 common between 36 m and 55 m. 



Young-of-the-year recruited in inshore waters 

 during the spring and moved towards deeper 

 water as they grew. Recently hatched fish 20-50 

 mm TL appeared only in 18-27 m depths in the 

 period February-May (Fig. 9), but became dis- 

 tributed as deep as 36-47 m by June to Septem- 

 ber. The larger young-of-the-year continued to 

 disperse gradually to deeper water as indicated 

 by their size gradients with depth in June-Sep- 

 tember 1979 and in October 1979-January 1980. 



Adult S. caprinus reside and spawn in waters 

 deeper than 27 m. No adults were found in 

 waters shallower than 27 m during the January- 

 April spawning period (Fig. 9). Fish of ages I and 

 II occurred in waters deeper than 27 m through- 

 out the year but showed no size gradient with 

 depth. This indicates that they were uniformly 

 mixed throughout the 27-100 m depth range. 



Stenotomus caprinus appear most vulnerable 

 to trawling at night. Mean catch per tow at night 

 in the 18-100 m depth range that S. caprinus 

 occupies averaged three times that of day catches 

 on 10 of 11 occasions in the period December 

 1978-March 1980 when day and night cruises 

 were made each month or close together in time 

 (Fig. 2). 



531 



