YELLOW PERCH OF LAKE ERIE 



255 



Erie 3'el]osv perch is based entirely on specimens 

 taken from impounding nets since, as will be 

 shown later (p. 258), the type of gear employed 

 influences the average value of K and gill nets are 

 particularly selective in this respect. 



Sex and stage of maturity wei-e shown by sepa- 

 rate analyses to have had very little effect on the 

 value of K except in the spawniing period. The 

 data in table 31 showing the montldy fluctuations 

 in condition of Lake Erie yellow perch according 

 to year of capture therefore, include individuals 

 for which sex or stage of maturity was not re- 

 corded. The data from samples obtained during 

 April 1932, October 1934, and November 1937 

 are not shown in the table because each of those 

 years was represented by only 1 month. The 

 values of /v for these 3 months were 2.24 (133 fish), 

 2.24 (207 fish), and 2.18 (131 fish), respectively. 



Annual fluctuations in condition and differ- 

 ences with respect to the months represented in 

 the various years' collections place limitations on 

 the conclusions to be drawn from the data of table 

 31. Nevertheless, certain trends can be detected. 

 It is obvious, for example, that perch tend to be 

 in better condition in midsummer and late summer 

 than in June. This is brought out by the follow- 

 ing tabulation of the unweighted averages of K 

 for corresponding months of 1928 and 1929: 



Average K 



September 1 . 96 



October 1.92 



Ax'eruge K 



June 1.80 



July 1.97 



August 1.98 



November 1. 87 



The montlily averages for the 2 years show a 

 great improvement in condition from June to 

 July. Condition remained good in August and 

 September. The average K decreased shghtly 

 in September and undei-went a greater decrease 

 in October and November. The averages in 

 table 31 show that the October-November decline 

 was much more pronounced in 1929 than in 1928. 



The averages for September, October, and 

 November, 1927, suggest that loss of condition 

 in tlie autumn may not be typical for the Lake 

 Erie perch. In 1927 the value of iiC increased in 

 both October and November. The averages for 

 the 1930 collection, on the other hand, agreed with 

 the trend of the 1928-29 averages. In 1930 the 

 value of K increased markedly in July and re- 

 mained at a high level in August and September. 

 The only available comparisons of the averages 

 of A' for November and December (1929) indicate 



Table 31. — Monthly values of K (condition) of Lake Erie 

 yellow perch taken in impounding nets, 1927-30 



Month 



April 



May 



June.- 



July___ 



August 



September. 



October 



November. 

 December. . 



.\verape. all months... 



.\verage, excluding 



April and May 



1927 





125 

 895 

 496 



1,616 

 1,516 





1.87 

 1.91 

 2.01 



1928 



1929 



I" 



429 

 664 

 504 

 132 



510 

 162 

 458 

 264 



3,123 

 2,030 



>^ 



1.78 

 1.76 

 1.81 

 2.06 

 2,04 

 2.00 

 1.9» 

 1. 



1, 

 1.96 



aS. 



3,122 



1,841 



2,747 



1.820 



451 



126 



691 



417 



11,215 



8,093 



So 



1.84 

 1.78 

 1.88 

 1.92 

 1.93 

 1.86 

 1.78 

 1.88 



1.85 



1. 



41 

 5 

 173 

 25 

 25 



269 

 228 



1.85 

 1.81 

 2.31 

 2.34 

 2.33 



2.24 

 2.30 



an improvement in condition m the latter month. 

 Three comparisons are available of condition in 

 May and June and one of condition in April and 

 May. However, the possible distm-bing effects 

 of variations in the relative abundance of giavid 

 and spent fish in the various AprU and May 

 collections make it inadvisable to draw con- 

 clusions concerning montlily changes in condition 

 from April to May and from May to June. 



The grand averages for K in the different 

 years' collections are not strictly comparable 

 because of dift'erences from year to year in the 

 months represented. A more reliable estimate 

 of the annual fluctuations in condition may be 

 had from comparisons of averages for correspond- 

 ing months. Comparisons of the averages for 

 September, October, and November indicate 

 that condition was slightly better m 1928 than in 

 1927. The large 1928 advantages in September 

 and October overshadowed the 1927 advantage 

 in November. Condition was poorer in 1929 than 

 in 1928. The K averages were lower in 1929 in 

 every month except May. The condition of the 

 Lake Erie perch in 1929 was also proliably poorer 

 than in 1927. The September average was higlier 

 in 1929 than in 1927, but the October and Novem- 

 ber averages were both higher in 1927. The 

 best condition of the 4 years occurred in 1930. 

 With the exception of June which had the same 

 K averages in 1928 and 1930, the montlily averages 

 in 1930 were consistently greater tlinn the cor- 

 responding averages in any other year. From 

 the data just discussed it would appear that the 

 probable order of the 4 years with respect to 

 condition of the Lake Erie yellow perch from 



