NOTE Marcogliese et al : Use of parasites in the identification of stocks of Sebastes mentel/a 



185 



The following analyses were performed. For each pair of 

 geographically adjacent management units, that is, across 

 the four stock boundaries encountered around Newfound- 

 land (See Fig. 1), fish were divided into 1-cm length classes. 

 For a given comparison, only length classes containing fish 

 from both units involved were retained. Within each class, 

 the parasite infection intensities were attributed standard 

 normal ranks. The ranks from all length classes were then 

 combined to perform a Mest. This test corrects for the 

 effects of host size on parasite mean abundance and for 

 variance heterogeneity while preventing outlying obser- 

 vations from having too much influence. The multiplicity 

 of the statistical tests (many pairs of stocks multiplied by 

 many parasites) was accounted for by a bootstrap proce- 

 dure (PROC MULTTEST, SAS, version 8, SAS Institute, 

 Inc., 1999). The numbers of fish from each length class 

 involved in the comparisons are detailed in Table 2. 



Intensity refers to the number of parasites of a given 

 species in an infected individual fish and mean intensity 

 refers to the mean number of parasites of a given species 

 per infected fish in a sample. Mean abundance is defined 

 as the mean number of parasites of a given species per 



host, infected and uninfected, in a sample. Prevalence is 

 the proportion of fish infected with a given parasite in a 

 sample, expressed as a percentage (Bush et al., 1997). 



Results 



Sixteen taxa were found to infect S. mentella in eastern 

 Canada in this survey. These included one myxozoan 

 (Ceratomyxa sp. ), eight digeneans (Anomalotrema koiae, 

 Derogenes varicus, Hemiuris levinseni, Lecithaster gib- 

 hosus, Lecithophyllum botryophorurn, Olssoniiim turneri, 

 Podocotyle reflexa, and Progonus muelleri), two cestodes 

 (Bothriocephalus scorpii, and Scolex pleuronectis plerocer- 

 coids), three nematodes (Anisakis simplex, Contracaecinea, 

 and Hysterothylactum aduncum ), and two copepods iChon- 

 dracanthus nodosus and Sphyrion lumpi). This is the first 

 report of O. turneri and P. muelleri from Sebastes spp. 



Preliminary analyses demonstrated that only larvae of 

 Anisakis simplex and Hysterothylacium aduncum, both 

 anisakid nematodes occurring on the viscera of fish, and 

 the copepod ectoparasite Sphyrion lumpi could be used 



