FISHERY BULLETIN; VOL. 86, NO. 3 



300 



£ 200 



£ 



X 

 I- 



o 



z 

 111 



_J 



m 

 O 



z 



^ 100 



50 



KnL = 5.95e 



0.0504 / ^(-0.0128(l-5))\ 

 0.0128^^"® ' 



I <114 



0.0865 / {-0.0293{l-5))\ 



KnL = 5.90e 0.0293 ^^'^ ' 



0.0592 / (-0.0126(1-5))) 



KnL = 3.01e 0.0126^^"® 



KnL: KNOB LENGTH 



I: NUMBER OF INCREMENTS 



50 



100 



200 



300 



400 



NUMBER OF INCREMENTS 



Figure 4.— Growth curve of the western Pacific saury. 



DISCUSSION 



The microstructure of otolith growth increments 

 of the Pacific saury is similar to that of daily incre- 

 ments in some other fishes (Nishimura et al. 1985). 

 Thus, the following discussion is based on the 

 assumption that the increments are daily growth 

 rings. A rearing experiment of larval sauries is 

 under way in the senior author's laboratory to verify 

 daily periodicity of the increment formation. 



Formation of a few embryonic growth rings or a 

 lamellar structure has been reported in California 

 grunion, Leuresthes tenuis, (Brothers et al. 1976); 

 mummichog, Fundulus heteroclitus, (Radtke and 

 Dean 1982); and walleye pollock, Theragra chalco- 

 gramma, (Nishimura and Yamada 1984). Radtke 

 and Dean (1982) mentioned that deposition of 

 growth rings in the embryonic stage might be 



related to a long incubation period. Pacific saury has 

 a long incubation period— about 17 days under 

 13.5°-15.7°C (Yusa 1960). At this temperature, eye 

 pigmentation begins 7 or 8 days before hatching, 

 and pectoral fins show constant movement from 5 

 or 6 days before hatching (Yusa 1960). Notochord 

 flexion occurs about midway through embryonic 

 development at 14°-22°C (Uchida et al. 1958). Thus 

 saury is more advanced at hatching than killifish 

 based on the embryonic development of killifish 

 reported by Armstrong and Child (1965). Observ- 

 ing the central area of otoliths, we found four faint 

 rings and a dark ring immediately outside of those 

 rings. We assumed therefore that the four faint 

 rings are embryonic rings and the dark ring is the 

 hatching ring. This assumption may be confirmed 

 by examining otoliths of late embryos and newly 

 hatched larvae of saury. 



494 



