542 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



small and sometimes hard to find. Fin rays 

 were counted in the dorsal and anal fins and both 

 pectoral fins. In counting the (soft) rays, each 

 element was counted as one ray. The last (most 

 posterior) two elements in the dorsal and anal 

 fins are well separated at the visible base of the 

 fin, not jointed or branched as in some groups of 

 fishes, and hence were counted as separate rays. 



Numbers of lateral plates are shown in table 2. 

 The Karluk Lake fish have from 5 to 9 plates, 

 with no specimen having 4. The mean for 200 

 specimens is 6.55. The fish from Bare Lake have 

 from 4 to 7 plates, no individuals having 8 or 9. 

 The mean for 200 specimens is 5.22. 



Between the various pairs of subsamples from 

 Karluk Lake, there are significant differences 

 (for the most widely separated pair, subsamples 

 r and rf, f=8.0 and P<0.001). The subsamples 

 were captured at different places on a large lake 

 and probably represent separate subpopulations. 



~-JU 



The means for the samples of 200 fish each 

 from the 2 lakes differ by 1.33. The difference 

 is highly significant (£=16.8; P<0.001). 



For the sample from O'Malley River, the mean 

 number of lateral plates lies between the ex- 

 tremes for Karluk Lake. 



The number of dorsal spines has a high degree 

 of constancy. Of 400 specimens from the 2 lakes, 

 391 had 3 spines, only 9 (2.2 percent) had 4 

 spines, and none had 5 or 2. The fourth spine, 

 when present, may be small and near the last 

 spine, or it may be almost as long as the middle 

 spine and be inserted midway between the last 

 2 of the 3 normal spines (fig. 3). The fourth 



A-JL, 



Figure 3. — Insertion of dorsal spines. Top, normal posi- 

 tion of 3 spines. Center, fourth spine about the same 

 size as, and inserted just posterior to, the second spine. 

 Bottom, fourth spine small and inserted just anterior to 

 third spine. 



spine was not found to occupy a position anterior 

 to the first normal spine or between the first two. 

 Counts of rays of the dorsal, anal, and pectoral 

 fins are summarized in tables 3-5. In the num- 

 bers of dorsal and anal fin rays, there are differ- 

 ences, of varying degrees of significance, between 

 the means of various subsamples from a given 

 lake. These differences, however, definitely are 

 overshadowed by the differences between the 

 means of Karluk Lake and Bare Lake. In each 

 of the latter instances, there is almost one fin 

 ray difference, the mean number for Bare Lake 

 beine lower than that for Karluk Lake. The 



to 



mean for the O'Malley River sample falls be- 

 tween the means for Karluk and Bare Lakes, for 

 dorsal and for anal rays. 



