FISHERY BULLETIN: VOL. 80, NO. 4 



125 



NEWPORT 



-FL 44-46 



• • • 



'SIUSLAW R. 



44 c 



43 c 



Figure 1.— Location of the 56 purse seine sets made by the FV 

 Flamingo (FL), 18-29 June 1979. Three geographical regions 

 were arbitrarily defined as northern (FL 1-24), central (FL 

 25-46), and southern (FL 47-56). 



were collected in the sets. Stomach contents of 

 220 juvenile coho, 147 juvenile chinook, and 41 

 juvenile chum salmon were examined. 



Whole fish <35 cm FL were preserved at sea, 

 after slitting the body cavity, in a 5-15% Forma- 



lin 4 -seawater mixture. In the laboratory, all 

 juvenile salmonids were identified to species, 

 measured (fork length), and stomachs removed. 

 Relative stomach fullness was visually estimated 

 on a scale of 0-3 (where = empty; 1, 2, and 3 = 

 fullness in thirds; distended stomachs = 3). State 

 of digestion was noted as one of three subjective 

 categories: Well-digested, partially digested, or 

 fresh. Due to the possibility of differential diges- 

 tion times of prey items, categorization of state 

 of digestion probably has little meaning except 

 for the "fresh" category. 



Food items were identified to the lowest pos- 

 sible taxonomic level and enumerated. Crusta- 

 ceans and fishes were also identified to develop- 

 mental stage. Standard length of all fish prey 

 was measured as well as total length of most of 

 the invertebrate taxa from the coho salmon stom- 

 achs. Euphausiid lengths were measured from 

 the posterior edge of the eye socket to the tip of 

 the telson. Stomach contents of all salmonids 

 were sorted into major taxonomic groups, damp- 

 dried on absorbent paper, and weighed to the 

 nearest 0.01 g. 



RESULTS 



Occurrence and Abundances of Prey Taxa 



Table 1 lists the average abundances of major 

 taxa of prey in salmonid stomachs and the aver- 

 age length and length ranges of fishes examined. 

 Euphausiids, amphipods, and crab larvae were 

 the most numerous taxa in the stomachs of juve- 

 niles of all three species. Fishes were the only 

 other major taxa found in all juvenile salmon. 

 Numbers of fish per stomach were low. On a 

 weight basis, fishes were the most important prey 

 for juvenile coho and chinook, followed by eu- 

 phausiids (Table 2). Chum stomachs contained 

 mostly euphausiids and amphipods. 



Based on percent frequency of occurrence of 

 prey in stomachs, euphausiids occurred in 85% of 

 all chum stomachs, 63% of coho stomachs, and 

 about 50% of chinook and steelhead stomachs 

 (Table 2). Amphipods also ranged in frequency 

 of occurrence from 56 to 32% among these same 

 species. The occurrence of fishes, on the other 

 hand, ranged from 10% of the chum stomachs to 

 69 and 71% in coho and chinook stomachs, respec- 

 tively. 



4 Reference to trade names does not imply endorsement by 

 the National Marine Fisheries Service, NOAA. 



842 



