LAROCHE and RICHARDSON: REPRODUCTION OF NORTHERN ANCHOVY 



mature northern anchovies (130 and 141 mm SL) 

 captured in July (Figure 6). Four maturation 



CO 



UJ 



I- 

 >- 



o 

 o 



50 - 

 45 - 

 40 - 

 35- 

 30 - 

 25 - 

 20 



15 



10 



5 







UJ 



m 



-ih 



40 



35 



30 



25 



20 

 15 

 10 - 

 5 - 

 oIa- 



STAGE 7 



\< 



'm 





I30mm SL 

 24 July 1975 

 N=486 



!» 

 ^ 





m", 



iK 



'\:M;.ik^:MA.X>'\X<: 



..i >y '.-J 



ji 



•3J 



STAGE 8 



v\ 



•i> 



'.vT tV 



■-^m.- 



w% 



141 mm SL 

 24 July 1975 

 N=4I7 





^ 







ro 



O 



d 



00 U3 



^ IT) 



d d 



CD 



d 



CJ 



o 



CO 



d 



(D 

 00 



d 



OOCYTE LENGTH (mm) 



Figure 6. — Size-frequency histograms of all completely opaque 

 oocytes in weighed subsamples from two northern anchovies, one 

 in ovarian stage 7 and one in ovarian stage 8. (N = total number 

 of oocytes measured.) 



stages among yolked oocytes were found in E. 

 japonicus after inspection of histological prepara- 

 tions, a more precise method, which were found to 

 coincide with stages of ovarian development based 

 on oocyte size composition (Usami 1963). At 50 x 

 magnification the general appearance of oocytes 

 from the two mature, northern anchovies was the 

 same but inspection of the size distributions indi- 

 cated two groups. In the 130 mm fish, two modes of 

 oocytes were apparent but not distinctly separate. 

 But in the 141 mm fish, after additional growth the 

 mode of larger oocytes became distinct and were 

 probably ready to undergo hydration and ovula- 

 tion subsequent to spawning. 



Fecundity 



Estimates of fecundity were made on only the 

 ripest northern anchovies, ovarian stages 6-10, 

 captured in July during the spawning season 

 when recruitment of yolked oocytes to the most 

 advanced mode was nearly complete (Table 5). 

 Fish in stages 6-8 used for fecundity determina- 

 tions had not spawned recently as evidenced by 

 the absence of empty follicles or degenerating ripe 

 oocytes in their ovaries. Oocytes in stage 10 fish 

 had not been ovulated yet; therefore, none had 

 been lost because of spawning or handling during 

 capture. 



The mean total fecundity of 21 northern an- 

 chovies was 16, 826± 1,563 oocytes, and mean rela- 

 tive fecundity was 720 ±40 oocytes/g total body 

 weight or 826±49 oocytes/g ovary-free body 



Table 5. — Data for 21 female northern anchovies, Engraulis mordax, collected off the Oregon-Washington coast in July 

 1975-77 used to estimate fecundity. Gonadal index (1) and relative fecundity (1) were calculated using body weight + ovary 

 weight. Gonadal index (2) and relative fecundity (2) were calculated using ovary-free body weight. 



611 



