30 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



the (lisajiroemoiits bctwopii readings miglit liave 

 been eliminated. 



AGREEMENT BETWEEN AGES READ FROM SCALES 

 AND AGES FIXED BY DEFORMED FINS 



The final readings of the lake trout scales agreed 

 witli the supposed ages of the fish for 1,319 of the 

 1,405 or 93.9 pereent of the specimens from nor- 

 tliern I^ake Michigan. The presumed age is fk'- 

 termined as the time between tiie date of capture 

 and the year tlie fish would have been liatclied if 

 the damaged fin were a true mark of identification. 



Detailed information is given in tal)le 9 for the 

 86 lake trout for whicii the supposed ages and the 

 ages as read from the scales were in disagreement. 

 Of this numlier, 9 fisii (indicated by asterisks in 

 the talile) were so large in relation to their sup- 

 posed age tiiat it may be assumed with confidence 

 that they were unmarked fisii with malformed 

 fins. No de])en(lal)U' objective standard was 

 found from which to judge wlietlier or not the re- 

 maining 77 lake trout were iiona fide recoveries of 

 marked lake trout. They must accordingly be 

 classed collectively as of "uncertain status." 

 Data presented in a later section, however, give 

 evidence that a large percentage of these fish liad 

 not been marked. 



A summary of the discrepancies in age with 

 respect to the degree of divergence (including the 

 9 fish designated in table 9 as too large for their 

 supposed age) is given in table 10. Disagree- 

 ments on age were mostly of 1 year (68.6 percent): 

 but were of 2 years for 18.6 percent and more than 

 2 years for 12.8 percent. 



T.\BLE 9. — Inforiiintion on SfS lake trout from northern Lake 

 Michigan for which aqe indicated by the mark did not agree 

 with age read from the scales 



[Asterisks designate fish that obviously were too large in relation to their 

 supposed ages to have been bona fide recoveries of marked fish] 



T.\Bi,E 0. — Information on 86 lake trout from northern Lake 

 Michigan for which age indicated hi/ the mark did not agree 

 with age read from the scales — Continued 



Total 

 length 

 (inches) 



17.5 

 1.5.4 

 14.8 

 13.3 

 11.7 

 11.5 

 11.2 

 10.8 

 10.0 

 9.5 



22.0 



lfi.8 

 15.9 

 12.7 

 12.7 

 12.1 

 12.1 

 11.9 

 11.6 

 11.3 

 11.0 

 14.1 

 21.8 



20.5 

 20.0 

 19.3. 

 18.2. 

 18.0 

 16.1 

 16.0 

 15.6. 

 14.7 

 13.9 

 12.5. 

 12.1. 

 11.7. 

 9.7 

 18.0. 

 14.9. 

 14.3. 

 13.4. 

 13.1. 

 12.0. 

 17.3. 



14.4 

 13.7, 

 13.0. 

 12.S. 

 11.8. 

 11.8. 

 20.0. 

 19.4. 

 19.0. 

 18.8. 

 18.7. 

 18.6. 

 18.0. 

 17.0. 

 17.0. 

 16.3. 

 14.0. 

 13.8. 

 12.4. 

 12.2. 



11.3. 

 11.2. 

 10.8. 

 13.4- 

 13.0- 



Sup- 



posed 



age 



Age 

 read 

 from 



Year 

 marked' 



Condition of fin 



1945 

 1945 

 1945 

 1945 

 1945 

 1945 

 1945 

 1945 

 1945 



No regeneration, or fin missinfr. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 

 Little regeneration. 

 No information. Fin scar not seen in 



Ann Arhor. 

 No regeneration, or fin missing. 



Do, 

 l^ normal length, 8 rays. 

 '/4 normal length, 1 curved ray. 

 ^ii normal length, 10 twisted rays. 

 \i> normal length, rays twisted. 

 !^ normal length, 4 twisted rays. 

 Ml normal length, fi twisted rays. 

 H normal Irntzth. 12 twisted rays. 

 No regt'niTation. or fin missing. 

 H inch long, 1 twisted ray. 

 Adipose missing, 4 rays in dorsal. 

 34 normal length, some rays fused 



and curved. 

 34 normal length, fi twisted rays. 

 S rays. 



Xo regeneration, or fin missing. 

 H normal length, 4 rays. 

 ^4 normal length, H rays, 

 Xo regeneration, oi' fin missing. 



Do. 



Do. 

 Almost normal length, 7 rays. 

 H normal length, 9 twisted rays. 

 \i normal length, ray^ twisted. 

 No regeneration, or fin missing. 

 V-i inch long, 7 rays. 

 \\ inch long, 1 curved ray. 

 X^o regeneration, or fin missing. 

 ^i normal length, H rays. 

 \i normal length, fi rays. 

 X'o regeneration, or fin missing. 



Do. 

 H inch long. 2 twisted rays. 

 Adipose missing, dorsal normal 

 length but with all rays crooked 

 ^6 distance from back. 

 Adipose torn, dorsal normal. 



Do. 



Do. 

 Adipose missing, dorsal normal. 

 Adiposi- small, dorsal normal. 

 Adipose missing, dorsal normal. 

 J.4 inch long. 2 twisted rays. 

 i^ normal length, b rays, 

 Xo regeneration, or fin missing. 



Do. 



Do. 



Do. 

 },-2 inch long, 2 twisted rays, 

 i.^ normal length. ^ rays. 

 No regeneration,- or fin missing 

 H normal length, 2 rays. 

 ^1 normal length, rays broken. 

 Normal length. 



H norma! length, 4 curved rays. 

 ^4 normal length, 8 normal rays, fi 



twisted ravs. 

 34 normal Irngth. 14 iwisted rays. 

 ^4 normal length. 9 rays, 

 ^^ normal l*'ngth. 3 twisted rays. 

 ^^ normal length. 10 rays. 

 3i norma! length, 9 twisted rays. 



Table 10. — Smriwary of (he extent of disagreements on lake 

 trout showing discrepancies between supposed ages and 

 those read front the scales 



Areas 1-fi 



