FISHERY BULLETIN: VOL. 71, NO. 4 



WEIGHT-LENGTH RELATIONSHIP 



Logarithmic functions describing the expo- 

 nential increase ii] weight with increasing 

 length according to sex and gonadal condition 

 were calculated (Figure 7). These plots indicate 

 that logarithmic transformation of weight and 

 length give a linear relation. About 89 to 99% 

 of the variation in weight is associated with 

 variation in length of pre- and post-spawning 

 puffers of each sex. Puffers of both sexes were 

 heavier after recovery from spawning (late 

 July to November) than fish of comparable 

 length before spawning (April to early July). 

 Covariance tests (Mottley, 1941) indicated that 

 this difference in weight was not significant 

 in females but was in males at the 5% level. 

 A large increase in muscle and liver tissue 

 occurred during the growing season but was 



4000- 



zrs— I 



250- 



225- 



200- 



175- 



W 150- 



q: 



u 





125 — 



100- 



75- 



50- 



25- 



l,= 282(i-e"°-^°7^*^0 0659), 



1613) 



' - ^^ ^ ^ 



1 1 — 



H JE 



AGE GROUP 



IS 



Figure 6. — Growth curves of female (A) and male (B) 

 northern puffer fitted by the von Bertalanffly growth 

 equation and plots of increments in length of females (C) 

 and males (D) (circles represent calculated lengths). 



FEMALES 



MALES 



3000- 



2000H Post Spowning_ 

 N-- 180 

 Log w: -4 133 



.2 787 Log L 

 0.9682 



1000- 



500- 



^ 400- 

 CA 



I 300- 



o 



200- 



X 



o 



100- 



50- 

 40 



30- 



20- 



Pre Spawning 



N:|68 I 



Log W= -4.414 I 



 2 901 Log L 

 '^0 9820 



r-m — 



60 100 



1^ 



Log L 



200 300 



200 300 60 



LENGTH (mm) 



Figure 7. — Weight-length relationships for northern 

 puffers in postspawning condition (late July to November) 

 and in prespawning condition (April to early July). 



not quantified. By November fish appeared | ' 

 more robust and had larger livers than in April, i 



ACKNOWLEDGMENTS 



The authors express their appreciation to j 

 John V. Merriner, Mark Chittenden, Jr., Jo- t 

 seph G. Loesch, George C. Grant, and John J. t 

 Norcross for their counsel and criticism of 

 the manuscript. 



LITERATURE CITED 



Appelget, J., AND L. L. Smith, Jr. 



1951. The determination of age and rate of growth 

 from the vertebrae of the channel catfish, Ictahirus 

 lacustris piinctatus. Trans. Am. Fish. Soc. 80: 

 119-139. 

 Daiber, F. C. 



1960. A technique for age determination in the skate 

 Raja ei^Iaiuerici. Copeia 1960:258-260. 



962 



