necessary. Where the number of para- 

 sites is great, it seenns that, balancing 

 the cost of labor to remove the affected 

 portion, plus the loss of weight from 

 the fillet, against the value of the fillet, 

 the best course is to discard the fillet 

 altogether. 



Detection and Removal of Parasites 



Table 4 summarizes the data derived 

 from exannining fillets for parasites 

 with and without candling. The advan- 

 tage of using a candling table is obvious 

 from these results. 



No effective substitute for hand trim- 

 ming of the parasites has been devised 

 as yet. 



SUMMARY 



southern area as follows: 39 percent 

 for the northern area, 21 percent for 

 the middle area (Cape Cook to the 

 Columbia River), and 15 percent for 

 the southern area. 



Two theories can account for the 

 geographical distribution of the major 

 parasite, Prosorhynchus. One relates the 

 abundance inversely with the intensity 

 of fishing. The second suggests that 

 there is a geographical limit on the 

 parasite or on one of its hosts. The 

 economic importance of the problem 

 indicates the advisability of a study to 

 determine which, if either, of the two 

 theories is correct. 



Candling was found to be much more 

 effective than unaided visual inspection 

 in the detection of parasites in fillets. 

 Without the aid of candling, the in- 

 spector missed half of the parasites 

 present. 



The parasites Prosorhynchus sp., Por- 

 racaecum decijii.ens, and an unidentified 

 copepod cause considerable economic 

 loss in the Pacific rockfish industry. 

 These parasites are not harmful to 

 man, but their presence in rockfish 

 fillets is aesthetically objectionable. 



In a study made during the summer 

 of 1958 on rockfish taken in the area 

 from Hecate Strait to Cape Blanco, 

 Oregon, it was found that the incidence 

 of parasitization for Sebastodes alutus 

 ranged from the northern area to the 



Most of the infested fish had one or 

 two parasites. The number of parasites 

 per parasitized fish was greater in 

 fish caught in the northern fishing area 

 than in those caught in the southern 

 area. The parasites tended to be lo- 

 calized in the tail section of the fillet 

 and in the meaty shoulder section. The 

 tail sections can be discarded with 

 little economic loss, but the shoulder 

 section poses more of a problem. No 

 effective substitute for hand trimming 

 to remove the parasites has been de- 

 vised. 



MS #918 



10 



GPO 69660 1 



