Key to Field Identification of Anadromous Juvenile Salmonids 



in the Pacific Northwest 



By 



ROBERT J. McCONNELL and GEORGE R. SNYDER 



National Marine Fisheries Service 



Northwest Fisheries Center 



2725 Montlake Boulevard East 



Seattle, Washington 98102 



ABSTRACT 



A key is jn-esented with descriptive illustrations to help in field identification 

 of live, juvenile salmonids in fresh waters of the Pacific Northwest. Other juve- 

 nile fish that may be mistakenly identified as salmonids are included. 



INTRODUCTION 



Species identification of live, anadromous 

 juvenile salmonids is frequently a problem to 

 the field biologist. The purpose of this key 

 is to list and illustrate the external character- 

 istics which will expedite field identification 

 of juvenile salmonids in the Pacific Northwest. 



Five species of Pacific salmon (pink, chum, 

 sockeye, chinook, and coho) ; four species of 

 trout (cutthroat, brown, Dolly Varden, and 

 rainbow or steelhead) ; and otlier juvenile and 

 adult fish ' that may be mistaken for salmon or 

 trout in fresh water are described in this key. 



USE OF KEY 



The characteristics for identification are list- 

 ed in a series of alternative statements, some 

 of which are illustrated. To use the key, ex- 

 amine the first statement; if applicable, pro- 

 ceed to the next and continue to successive 

 statements until the species is identified. If 

 a statement is not applicable, ]iass to the alter- 



' Especially adult smelt, family O.smeridae. 



native characteristics indicated by numbers in 

 parentheses (numbers on the drawings corres- 

 pond to numbers of statements in the key). 

 Continue in this manner until the specimen is 

 identified. Some external characteristics are 

 positive separating features (marked with as- 

 terisk ) , whereas others are not. Therefore, two 

 or more statements should be considered before 

 final rejection. If a precise identification can- 

 not be made using the external characteristics 

 — and the fish can be sacrificed, a positive ident- 

 ification can usually be made from internal 

 features (marked with double asterisks). A 

 bibliography of keys that utilize more descrip- 

 tive internal characteristics is included in this 

 paper. 



KEY 



1. (47) Adipose fin and scales present. 



(Fig. 1) 



2. (48) Fleshy appendage at base of pelvic 



fins present. 



3. (49) Mouth large, reaching at least to 



center of eye. 



Family Salmonidae 



