o 



z 



LiJ 



ID 

 O 

 LU 



LU 

 > 



LlI 



day 



<# 



30-, 



25 



20 



15 



5- 



Anchoa mitchilli 1973 



N= 693 



TOS± SE= 16 8± 08 





"prrn^ I n^ I — 1 — I — I — I T^ I 



0.5 3.5 6.5 9 5 12 5 15 5 18.5 215 



Trt-n 



0.5 3.5 6.5 9.5 12.5 15.5 18.5 21.5 



day<* 



20 



15- 



Tauloga oni lis 1973 



N=447 

 TOS^SE - 17.6±.13 



nipht 



X ] 



Tn — I — I — I — I — I — r r I ' I I I 



0,5 3,5 6,5 9,5 12,5 15,5 18.5 21.5 



TIME OF SPAWNING 



( HOURS AFTER SUNRISE ) 



z 



LU 



13 

 O 

 LlJ 

 CC 

 U. 



UJ 

 > 



LjJ 



D 



FISHERY BULLETIN: VOL. 78, NO. 2 



day Q^ n I g h I 



20-1 



laulu g oldbrus adspersus 197- 



'^i N=322 r 



10 



TO^tSE- I6.0±. 22 



I ' I ' I ' I ' I I r r I ' I ' r I I 



0,5 3.5 6,5 9,5 12.5 15.5 18.5 21.5 



^ 



dav 



25 



20- 



15- 



10 



<♦ 



5- 



Pr ionotub spp. 1973 



N- 330 

 fOS±SE= 19. I ±.20 





11111111111 — I — 111 



0,5 3 5 6,5 9.5 12 5 15 5 18 5 215 



35 



30- 



25 



20 



15 



<$ 



day \Jvnight 



5 - 



Trinectes maculatus 1973 



N= 132 



TOS±SE= 16.6 ±.i I 



T 1 1 1 1 1 1 1 1 1 1 1 I I I 



n 



1 



I r I — I — r—r 



05 3,5 e.5 95 125 155 18,5 21 5 



TIME OF SPAWNING 



( HOURS AFTER SUNRISE ) 



Figure 2. — Relative frequency distributions of estimated spawning times (TOS) of (A) Anchoa mitchilli, ( B) Brevoortia tyrannus, (C) 

 Tautoga onitis, (D) Tautogolabrus adspersus, (E) Prionotus spp., and (F) Trinectes maculatus, determined by subtracting estimated 

 mean ages offish eggs <24 h old from their time of collection in 1973 samples. Mean day length during spawning seasons is indicated. 



DISCUSSION 



Direct observation of fish spawning at sea is 

 rare, and aquarium observations may not be 

 characteristic of natural spaw^ning or may be dif- 

 ficult or impractical to implement for logistic 

 reasons. Since embryogenesis begins at spawning 

 in most marine teleosts, the time of day spawning 

 occurs can be determined indirectly from the age 

 of embryos captured at sea. Several investigators, 

 including Ahlstrom (1943), Gamulin and Hure 



(1956), and Simpson (1971), collected plankton 

 samples throughout the day and determined 

 spawning times of fishes from the occurrence of 

 recently spawned eggs. Under certain cir- 

 cumstances (when field temperatures are fairly 

 constant and there is little translocation of eggs) 

 and with knowledge of embryonic development 

 rates, however, spawning times can be back calcu- 

 lated by subtracting age offish embryos from their 

 time of collection. The method of estimating 

 spawTiing time of fishes in this paper utilizes field 



458 



