NORTH AMERICAN SALMONIDAE 



239 



Table 3. — Results of crossbreed ing species of 



Oncorhynchus 



[First three columns from Foerster, 19351 



•Male hybrids matured and bred successfully with nerka females. 

 "Hybrids held to maturity. 

 •••Hybrids presumably held to maturity. 



1 Subjective ratings of relative success: 1 excellent, 2 good, 3 moderate, 4 

 poor, 5 very poor, 6 failure. 



COLORATION 



The fact that a great many taxonomic studies 

 liave necessarily been made on faded museum 

 specimens has tended to deemphasize the im- 

 portance of color in classification. Furthermore, 

 the heiglitening and changing of color in the 

 breeding season contrasted with the hiding of 

 color by the silvery guanin in marine species and 

 even during the lacustrine existence of adfluvial 

 species, has made color a sometimes unreliable 

 tool for field identification in the salmonids. 

 However, there are several color patterns in Sal- 

 monidae that may be diagnostic; the genetic in- 

 heritance of color in some taxa has been so well 



documented (for instance in Lehistes) that color 

 should be ti-eated with equal or perhaps greater 

 respect than many anatomical characters. In 

 this discussion we are not looking upon color 

 merely as a handy character for identification; 

 therefore, we are comparing coloration under 

 noi-mal conditions. Some of the moi-e evident 

 color characters of adults, not in breeding color, 

 are given in table 4. 



The presence on tlie body of black spots and 

 black speckling characterizes Oncorhynchus and 

 Salmo with the exception of S. trutta, which has 

 both the black spotting and the bright spots 

 otherwise reserved for the charrs. Since none of 

 the chan-s (including C list i vomer) shows black 

 spotting, tntfta is intermediate in this character. 



Rainbows and cutthroats agree in both the black 

 spotted tail and the bright lateral band. Both 

 chai'acters are absent in »S'. sahir and trutta. 



The dorsal vermiculations are conspicuous in 

 fontinalis and faint in aureolus and namaycush. 

 Tliis close association is coiToborated by the 

 hybridization experiments (fig. 1), which showed 

 fonfinalis closest to namaycush. 



The paiT markings of young Salmonidae are 

 often useful in field identification, despite the 

 considerable variation both in number and shape 

 of the marks (table 5) . 



Parr marks are absent in gorbuscha. This would 

 seem to be associated with the life history since the 

 young pink salmon normally proceed immediately 

 to the sea so that they are in effect not parr, but 

 very small smolts, when they emerge from the 

 gravel. This theory is somewhat strengthened by 

 the fact that keta, which is only slightly less an- 

 adromous than gorbuscha (Eounsefell, 1958), has 

 parr marks which are not as dark as those of 

 tsh-awytscha, kisutch, or nerka, and which com- 

 mence fading at an early age. 



Table 4. — Normal coloration in adult North American Salmonidae 



637056 O— 62- 



