YELLOW PERCH IN SAGINAW BAY 



385 



straight line passing through the origin. This 

 view was supported by the fact that the values 

 of the body-scale ratio, L/S (table 22), did not 

 show any trend with change of length. The 

 straight line of figure 11, therefore, was drawn 

 through the origin at a slope equal to the average 

 L/S value of 1.40. For these lengths above 70 

 the direct -proportion computations were 



Table 23. — Amount of correction to be added to direct- 

 proportion calculated standard lengths of yellow perch from 

 Saginaw Bay and Lake Eric 



nun. 



valid as calculated. For lengths less than 70 mm., 

 however (body-scale curve drawn freehand in 

 fig. 11) the direct-proportion calculation always 

 gave an underestimate of length. The amount 

 of correction required at a particular length can 

 be obtained by measuring the vertical distance 

 between the straight line and the empirical curve. 

 Table 23 was set up to show the correction for 

 each direct-proportion calculated length. 



Similar body-scale relations were determined 

 for the same key scale by Hile and Jobes (1941) 

 for Saginaw Bay and by Jobes (1952) for Lake 

 Erie. In both studies the relation for the larger 



Table 22. — Relation between body length (L) and the anterior 

 inlerradial measurement (S) of key scales of yellow perch 

 from above and from below the lateral line 



Standard 

 length 

 interval 



25-30 



31-35 



36-40..-. 

 41-45.... 



46-50 



51-55 



56-60 



61-65.... 

 66-70.... 

 71-75.... 

 76-80-.-. 

 81-85-... 

 86-90... 

 91-95... 

 96-100. . . 

 111-115.. 

 116-120.. 

 121-125. . 

 126-130.. 

 131-135.. 

 136-140. . 

 141-145. 

 146-150.. 

 151-155.. 

 156-160. 

 161-165. 

 166-170. 

 171-175. 

 176-180- 

 181-185- 

 186-190. 

 191-195. 

 196-200. 

 201-205. 

 206-210. 

 211-215. 

 216-220- 

 221-225. 

 226-230. 

 231-235. 

 236-240. 

 241-245. 

 246-250. 

 251-255. 

 256-260. 



Num- 

 ber of 

 fish 



1 

 3 

 8 

 1 

 1 

 2 

 4 



22 



19 



14 



40 



22 



17 



30 



45 



30 



48 



19 



7 



35 



14 



21 



7 



11 



9 



8 



6 



2 



9 



9 



4 



3 



2 



4 



2 



Average 



standard 



length 



Average scale 

 radius (x43) 



28.4 

 32.3 

 37.2 

 43.0 

 48.0 

 52.2 

 57.0 

 63.5 

 67.6 

 73.2 

 77.0 

 84.0 

 87.6 

 95.0 

 97.0 

 113.0 

 116.8 

 122.7 

 128.3 

 133.3 

 138.2 

 143.4 

 147.3 

 152.5 

 157.6 

 163.2 

 167.5 

 172.0 

 179.0 

 182.4 

 188.5 

 192.0 

 198.0 

 203. 1 

 208.3 

 212.8 

 218.5 

 223.0 

 227.0 

 232.6 

 238.2 

 245.0 

 248.0 

 252.0 

 257. 5 



Below 



lateral 



line 



8.8 

 11.4 



16.2 

 22.2 

 23.9 

 27.8 

 30.3 

 39.5 

 44.4 

 49.8 

 61.5 

 65.8 

 63.4 

 69.5 

 67.0 

 84.8 

 89.2 

 88.5 

 89.7 

 92.8 

 94.3 

 98.2 

 106.3 

 106.4 

 112.1 

 113.8 

 124.0 

 110.6 

 132.9 

 128.8 

 126.0 

 144.7 

 145.8 

 149.7 

 160.6 

 150.8 

 166.0 

 165.5 

 165.5 

 177.2 

 173.0 

 157.0 

 166.8 

 178.2 

 173.8 



Average LIS ratio 



Above 



lateral 



line 



4.6 

 6.6 



9.6 

 14.2 

 15.5 

 17.7 

 18.6 

 21. 1 

 23.0 

 28.2 

 34.5 

 36.0 

 37.2 

 38.5 

 41.0 

 52.8 

 71.6 

 61.4 

 59.4 

 65.3 

 64.4 

 70.5 

 71.6 

 76.2 

 76.6 

 78.1 

 79.9 

 79.8 

 89.7 

 90.9 

 84.0 

 95.0 

 99.1 

 105.2 

 112.4 

 108.5 

 115.7 

 118.8 

 125.6 

 133.5 

 141.5 

 107.9 

 127.0 

 133.0 

 135. 



Below 



lateral 



line 



3.23 



2.83 



2.30 



1.94 



2.01 



1.88 



1.88 



1.61 



1.52 



1.47 



1.25 



1.28 



1.38 



1.37 



1.45 



1.33 



1.31 



1.39 



1.43 



1.44 



1.46 



1.46 



1.3£ 



1.43 



1.40 



1.43 



1.35 



1.56 



1.35 



1.42 



1.50 



1.33 



1.36 



1.36 



1.30 



1.41 



1.32 



1.35 



1.37 



1.31 



1.38 



1.56 



1.49 



1.41 



1.48 



Above 



lateral 



line 



6.17 



4.89 



3.88 



3.03 



3. 10 



2.95 



3.06 



3.01 



2.94 



2.60 



2.23 



2.33 



2.35 



2.47 



2.36 



2. 14 



1.63 



2.00 



2.16 



2.04 



2. 14 



2.03 



2.06 



2.00 



2.06 



2.09 



2.10 



2.16 



2. 00 



2.01 



2.24 



2.02 



2.00 



1.93 



1.85 



1.96 



1.90 



1.88 



1.81 



1.74 



1.68 



2.27 



2.00 



1.89 



1.91 



1 Data taken from table 5 of Hile and Jobes (1941). 

 1 Data adapted from table 4 of Jobes (1952.) 



fish could be described by a straight line through 

 the origin but direct-proportion calculations gave 

 underestimates at the smaller lengths. The 

 amount of correction differed, however, between 

 Lake Erie and Saginaw Bay and between the 

 Hile and Jobes sample and the recent one from 

 Saginaw Bay. Without exception the corrections 

 determined in the present study were smaller 

 than those published for Saginaw Bay by Hile 

 and Jobes; furthermore, the 1955 samples indi- 

 cated no need for corrections beyond 70 mm. 

 whereas Hile and Jobes listed corrections through 

 101 mm. Differences between corrections at cor- 

 responding lengths averaged 4.5 mm. over the 

 range, 38-101 mm. The corrections of direct-' 

 proportion calculations at the smaller lengths of 

 fish for Lake Erie yellow perch were greater at 

 most lengths than those given by Hile and Jobes 

 for Saginaw Bay perch and were much larger 

 than those determined in the present study. The 

 average differences in the two comparisons were 



489035 O — 59- 



