SECOND SURVEY OF THE OCCURENCE OF PARASITES 

 AND BLEMISHES IN PACIFIC OCEAN PERCH, 

 Sebastodes alutus, MAY-JUNE 1959 



By 

 John Liston and Charles R. Hitz 



ABSTRACT 



A brief study was made of the occurrence of parasites and 

 blemishes in the Pacific Ocean perch, Sebastodes alutus, caught in 

 the waters of Hecate Strait and those southward to Cape Blanco, 

 Oregon, to test the findings made during a similar study in 1958. 



INTRODUCTION 



Parasites and blemishes (aberrant 

 tissue structures resembling in size 

 and appearance of an unpolished rice 

 kernel) are of common occurrence in 

 some species of fish. Although these 

 defects are harmless toman, the aver- 

 age consumer does not know this fact. 

 Furthermore, the presence of such 

 defects reduces the esthetic appeal of 

 the product. The result is economic 

 loss for the fishing industries. The 

 present series of investigations was 

 undertaken with the thought that greater 

 knowledge of these defects may help 

 the industries to reduce their loss. 



An initial brief survey on the extent 

 of parasitization and blemishes in fil- 

 lets of Pacific Coast rockfish, mainly 

 Sebastodes alutus, was carried out 

 during the summer of 1958 (Liston, 

 Peters, and Stern, I960).' The fish 

 used in that work were caught in the 

 waters of Hecate Strait and in those 

 southward to Cape Blanco, Oregon 

 (fig. 1). The parasites observed were 

 mainly Prosorhynchus and Porracae- 

 CUm, In addition, the incidence of 



Note." Charles R. Hitz presently employed with the 

 Exploratory Fishing and Gear Research Base, Bureau of 

 Commercial Fisheries, U. S. Fish and Wilflife Service, 

 Seattle, Washington. 



J Liston, John. John Peters, and Joseph A. Stern. 1960. 

 Parasites in summer-caught Pacific Ocean rockfish. U.S. 

 Fish and Wildlife Service, Special Scientific Report-- 

 Fisheries No. 352, July, 10 pp. 



blemishes, which occur in the muscu- 

 lature, was noted. Parasitization was 

 found to be greatest in fish taken in 

 the northern waters and least in those 

 taken in the southern ones. 



The purpose of the present study 

 was to check on the findings of the 

 first survey to see whether they could 

 be confirmed in the second year. 



PROCEDURE 



In the present study, methods and 

 sources of samples used were essen- 

 tially the same as those used in 1958. 

 Briefly, fillets of Sebastodes alutus 

 from known geographical areas' were 

 selected at random from the end of a 

 commercial filleting line and were 

 candled over an illuminated glass plate 

 to permit detection of parasites. In 

 addition, the incidence of blemishes 

 was noted. In order that the distribu- 

 tion of the defects could be recorded, 

 each fillet was arbitrarily divided into 

 areas- -A, B, C, and so on- -as illus- 

 trated in figure 2. 



One difference fronri the procedure 

 of last year was that many of the fillets 

 were examined unskinned, which is the 

 state in which one producer in whose 



'The geographical area^s were divided into northern- 

 Hecate Strait to Cape Cook, middle— Cape Cook to Colum- 

 bia River, and southern— Columbia River to Cape Blanco. 



