PENNELL. BECKER, and SCOFIELD: HELMINTHS OF KVICHAK SOCKEYE SALMON 



with methyl blue-lactic acid or cleared unstained 

 in lactic acid, and examined unmounted. Blood 

 and tissue smears were air dried, fixed in ab- 

 solute methyl alcohol, and treated with Wright's 

 blood stain. 



In this report incidence and intensity are used 

 to describe the percentage of infected hosts and 

 the average number of parasites per infected 

 fish, respectively. Incidences and intensities 

 were determined with confidence for the rela- 

 tively small smolts, but only the incidences were 

 judged to be reliable for the adult fish because 

 of difficulty in obtaining accurate counts of fre- 

 quently abundant helminths. 



To accurately determine the age of the host, 

 scales from smolts and otoliths from adults were 

 preserved and read for age, and the readings 



were checked against the recorded length of the 

 fish. The smolts were from the 1966 and 1967 

 brood years and were designated as age 2 and 

 age 1 according to the number of winters spent 

 in fresh water. The adults were from the 1963, 

 1964, and 1965 brood years and had spent either 

 two or three winters in the sea. 



RESULTS AND DISCUSSION 



Parasitological examinations were completed 

 on 212 smolts, 88 adults from Bristol Bay, and 

 71 adults from fresh water. The identities and 

 incidences of helminths in these fish are shown 

 in Table 1 under appropriate area and age des- 

 ignations. No haematozoa, myxosporidians, 

 microsporidians, leeches, or copepods were 



Table 1. — Incidence of helminths in young and adult sockeye salmon from the Kvichak River system in 1969. 



(Incidence in parentheses as a percentage.) 



! * = larvae (in fish intermediate host), ** = postlarvae (sexually undeveloped parasite). 



2 Age designation is bosed on Arabic numerals corresponding to the number of winters lived. Freshwater age precedes the dot, salt water age 

 follows the dot; i.e., 2.2 = adult, 2 winters in fresh water, 2 winters in the sea. 



3 Examination of adult sockeye for nematodes was restricted to the digestive tract, viscera and body cavity. 



* Incidence of P. oncorhynchi in smolts was based on larvae in the swim bladder,- in adults, on encystation of mature worms among the vis- 

 cera and on body cavity wall. 



^ Of nematodes preserved from Bristol Bay adult sockeye, the ratio (in total numbers) of P. oncorhynthi to Anisakis to Contracaecum was about 

 1:2:1.5. 



' Primarily Anisakis and Contracaecum in Bristol Bay adylt sockeye, primarily Anisakis in adults reaching fresh water. 



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