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FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



tory. The discrepancies were more pronounced 

 among larger fish, but on the whole, distribution 

 of the disagreements had no particular trend. 

 Jobes (1941) noticed that disagreements were 

 very large for Lake Erie perch beyond 11.8 

 inches total length, but attributed them to the 

 small number of fish. In addition, the hetero- 

 genity of the sample must be considered as the 

 cause of some disagreements because collections 

 of different years were combined in the determi- 

 nation of the length-weight relation. 



Weight in Relation to Condition of Gonads 



Information on the state of the gonads was, 

 unfortunately, not available for all the spawn- 

 ing-run samples. For this reason, only those for 

 1949, 1951, 1953, 1954, and 1955 could be used 

 for the study of the relation of weight to the 

 condition of the gonads. Annual variations of 

 weight in the 5 years were so small among fish 

 of the same length, sex, and the state of the 

 organs that the data were combined in the prepa- 

 ration of table 19. The insignificant difference 

 of weight between ripe and spent males justified 

 their combination as adult males. On the other 

 hand, the differences between ripe and spent fe- 

 males indicated a large percentage loss of weight 

 at spawning. The loss exhibited no clear-cut 

 trend with increase of length. This observation 



agreed with the finding of Jobes (1952) that no 

 relation exists between the percentage loss of 

 weight and the length of fish. 



The loss of weight of females at spawning 

 varied between 8.5 and 22.2 percent (a gain was 

 indicated at 5.5-5.9 inches but the comparison 

 was based on only 2 fish). Over the length in- 

 terval in which both unspent and spent fish were 

 represented by 9 or more fish in each comparison 

 (6.5-9.4 inches) the values ran from 8.5 to 16.7. 

 The average percentage loss for the whole sample 

 was 12.3 percent, much less than the 16.1 percent 

 recorded by Jobes (1952) for Lake Erie yellow 

 perch. 



The weights of the immature fish of both sexes, 

 of adult males, and of spent females all were 

 closely similar, and as noted, substantially below 

 those of ripe females of corresponding length. 



Seasonal Change in Weight 



Information on seasonal variation in weight 

 can be studied only for 1955, the 1 year with 

 collections outside the spawning season. Because 

 of their relatively greater weight, ripe females 

 are listed separately in the data on the length- 

 weight relation of spawning-run fish (table 20). 

 In later collections, however, the difference in 

 weight between the sexes was too small to war- 

 rant separate presentation. 



Table 19. — Length-weight relation of Saginaw Bay yellow perch according to sex and state of organ 

 [Based on spawning-run collections of 1949, 1951, 1953, 1954, and 1955. Number of fish in parentheses] 



1 All nuiture fish combined (nearly ripe fish omitted). 



2 Ripe and nearly ripe fish combined. , 



> In the computation of this average, each percentage was weighed by the sum of the number of fish in the 2 groups whose weights were compared to 

 obtain the percentage. 



