In all plants the workers were informed 

 of the purpose of the investigation in 

 order to enlist their cooperation. To 

 determine the distribution of parasites 

 in the fish, the fillets were arbitrarily 

 divided by imaginary lines into six 

 areas, as is shov/n in figure 2. Each 

 fillet selected was examined by re- 

 flected light, and the total number of 

 parasites observed was recorded. The 

 fillet then was examined on a candling 

 table, and the location and number of 

 parasites seen by this method were 

 noted. 



Fioure 2.— division of the fillet into arbitrarily areas 

 for parasite count. 



RESULTS 



Northern Area 



Fish taken from the northern area 

 were examined at Bellingham. A sample 

 of 805 fillets from 76,500 pounds of 

 ,S. nlutus were inspected. The data ob- 

 tained are shown in table 1 and figure 3. 



A few fillets of S.. melanops from the 

 area also were examined and were 

 found to be parasitized by PTosorliynclius. 

 This species is reputed to be so 

 heavily parasitized that plant operators 

 refuse to buy it except for mink food. 



Four thousand pounds oiS.pinniger 

 was landed by one boat, and 200 fillets 

 from this batch were examined. No 

 parasites of any kind were observed. 



In addition to I'Tosorhynchus and Pot- 

 racaecum, a parasitic copepod was ob- 

 served in Pacific ocean perch fillets 

 from fish taken in the northern area. 

 This parasite lies in the flesh encased 

 in a sac containing dark-colored fluid 

 (actually waste nnaterial) under pres- 

 sure. If the sac is ruptured during 

 filleting, the liquid spurts forth, some- 

 times as far as several feet. Fish 

 showing signs of this parasite normally 

 are discarded, and though the incidence 

 of the copepod is small (about 0.01 

 percent), it is a source of annoyance 

 and concern to the filleters. (The para- 

 site also was observed in Pacific ocean 

 perch from the southern area.) 



Middle Area 



Pacific ocean perch from the middle 

 area were examined at Seattle. A 



Table 1 -- Parasitic infestation of Pacific ocean rockfish 



