YELLOW PERCH OF LAKE ERIE 



213 



Table 2. — Specimens used in study of Lake Erie yellow 

 perch and gear employed in taking them 



1 In addition, 188 selected specimens were used In the key-scale study. 

 ' In addition, 79 selected specimens were used in the key-scale study. 

 ' 207 selected specimens were collected for key-scale study. 

 ' In addition, 126 selected specimens were used in the key-scale study. 

 i Selected specimens used in the key-scale study and for the determination 

 of maximum age are not included in the totals. 

 ' Q ill nets 22 meshes deep. 

 ' Oil] nets 100 meshes deep. 



600 specimens collected for the key-scale study 

 were not used for any other purpose, except the 

 207 collected October 4, 1934, which were em- 

 ployed as part of the data on the length-weight 

 relation. 



During 1927 and 1928 the lifting cribs of the 

 trap nets from which samples were taken were 

 made of 2-inch or 2Ji-inch webbing (stretched 



measure as manufactured), except for the vertical 

 middle third of the backs, where the mesh was 

 2% inches. From 1929 to 1937 the mesh of the 

 crib was 2^ inches (stretched measure as manu- 

 factured) in all parts except the entire back where 

 the mesh was 2Yi inches. Since 1937 the mesh in 

 the back of trap nets has been 2% inches, with the 

 sides made of 2}^-inch mesh. The pound-net 

 samples (from Erie, Pa.) were from nets with 

 meshes of 2'){6 inches (stretched measure as manu- 

 factured). The gill nets, from which the 1927-28 

 samples were studied, were of 3-inch and SKe-incb 

 mesh (stretched measure as manufactured). Since 

 the length frequencies of the perch taken in the 

 two sizes of mesh showed no significant differences, 

 the size of mesh was ignored in treating the gUl- 

 net data. The gill-net data, however, have been 

 separated on the basis of depth of net because 

 there was a difference between the length fre- 

 quencies of perch taken in shoal gill nets and in 

 bull gill nets. The shoal nets were 22 meshes deep 

 and the bull nets 100 meshes deep. The meshes 

 of the shoal nets from which the 1943-48 samples 

 were taken measured 2% inches. 



Except in 1930-31 and 1943-48, lengths were 

 measured with a flexible steel tape held so as to 

 foUow the curve of the body from the tip of the 

 snout to the thickest part of the body, and then 

 in a straight line approximately parallel to the 

 long axis of the body. The length records of fish 

 caught in 1930-31 and 1943-48 were obtained with 

 a measuring board. The lengths measured on the 

 board were converted to "tape-line lengths" by 

 the factor 1.02. Weights were recorded to the 

 nearest fourth of an ounce except in 1948 when 

 they were recorded in tenths of ounces. All meas- 

 urements of length and weight were obtained from 

 fresh specimens in the field, except those of fish 

 collected for key-scale study. Of those, the 207 

 used in the length-weight-relation study were 

 shipped fresh, packed in ice, to the laboratory, 

 where they were measured and weighed, and the 

 rest, all preserved, were measured but not weighed. 

 Lengths obtained from preserved specimens were 

 corrected for shrinkage produced by the preserva- 

 tive; the coiTcction factor was 1.0065. 



Scales for age determinations were taken from 

 the left side of the fisli, below the lateral Une and 

 beneath the spinous dorsal hn. The}"^ were 

 mounted on standard glass microscope sHdes in 



