fillet, with a few occurring near the 

 tail portion and none occurring in the 

 middle portions. 



The observed incidence of parasites 

 in Pacific ocean perch from the southern 

 area (15 percent) was lower than that 

 in fish from either the northern or the 

 middle area. Over 80 percent of the 

 infested fish had two or fewer parasites 

 per fillet, and the most heavily para- 

 sitized fillet observed contained only 

 six parasites. Again, fillets were para- 

 sitized most commonly in the tail por- 

 tion. 



Though, in this preliminary survey, 

 too few samples were taken for a 

 detailed statistical analysis that w^ould 

 yield truly definitive results, a simple 

 analysis of some of the individual catch 

 data listed in table 5 does illustrate 

 certain interesting points. The results 

 of the analysis are shown in table 6. 

 The standard deviations were calcu- 

 lated, using a mean weighted in each 

 case according to the population offish 

 sannpled (i.e. the hailed catch), on the 

 assumption that the sanriples were suf- 

 ficiently random to be representative. 

 Obviously, the northern area fish show 

 a consistently high level of parasite 

 infestation with little variation; the 



calculated range at 95 percent confi- 

 dence is only 33.48 to 43.0 percent. 

 The wide range indicated for middle 

 area fish might be evidence of an in- 

 termingling of more and less heax-ily 

 parasitized stocks of Pacific ocean 

 perch in this area. It could be concluded 

 similarly that there is an intermingling 

 of stocks of this type in the southern 

 area also, but the low value of the 

 weighted mean for this area probably 

 indicates a preponderance of lightly 

 parasitized fish. 



The high incidence of parasites in 

 Pacific ocean perch from the northern 

 area is \vell recognized in the industry 

 and is believed to be related to the 

 large size of the fish population in the 

 region, which in turn is believed to be 

 related to the total amount of fishing, 

 past and present, that has taken place, 

 there. The fishing intensity probably 

 has been less, over the years, in the 

 northern area than in the more southerly 

 grounds. Nevertheless, the area con- 

 tinues to be fished, since the abundance 

 of the catch compensates, no doubt, for 

 the losses due to parasites. 



The fish buyers in Astoria are aware 

 of the low parasitization of Pacific 

 ocean perch caught in the southernarea. 



Table Ij -- Examination of fillets with and without candling 



