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Fishery Bulletin 101(1) 



to discriminate among redfish stocks (SAS GLM proce- 

 dure, SAS, 2001). Gastrointestinal digeneans were not 

 used because differences were not noted among regions 

 (SAS GLM procedure). Furthermore, evagination of most 

 of the redfish stomachs during collection caused losses of 

 gastrointestinal parasites and rendered the worm counts 

 unreliable. Myxozoans and C. nodnsiis were not common 

 enough to be used as tags for deepwater redfish (1% and 

 2% prevalence overall, respectively). Sphyrion lumpi use 

 redfish as its definitive host but only adult females are 

 embedded permanently in the flesh, and sores of previous 

 infections were taken into account in our study. 



Larvae of A. simplex were common at almost all sites, 

 but were particularly abundant off Labrador, on the Flem- 

 ish Cap. and in the Gulf of St. Lawrence. The most preva- 

 lent and abundant parasite encountered was H. aduncum 

 in redfish from the Flemish Cap. The copepod S. lumpi was 

 most prevalent in the Gulf of St. Lawrence and the Lau- 

 rentian Channel Prevalence and mean intensity of these 

 parasites are shown in Table 3. 



Results of multiple nonparametric analyses demon- 

 strated that at least one of the three parasite species 

 differed in mean abundance between all adjacent areas, 

 with the exception of the Labrador Sea and the Gulf of 

 St. Lawrence. Mean abundance of both H. aduncum and 

 S. lumpi in redfish from the Flemish Cap and the Cabot 

 Strait-Laurentian Channel were significantly different 

 (bootstrap adjusted P<0.0001 and 0.01, respectively). 

 Mean abundance of//, aduncum al.so differed between fish 



from the Flemish Cap and the Labrador Sea (bootstrap 

 adjusted P<0.0.5). Lastly, mean abundance of A. simplex 

 differed between fish from the Gulf of St. Lawrence and 

 those from the Cabot Strait-Laurentian Channel (boot- 

 strap adjusted P<0.01) (Table 4). 



Given that the Gulf of St. Lawrence (unit 1) and the 

 Cabot Strait-Laurentian Channel (unit 2) populations 

 are currently managed as separate stocks, we wished to 

 validate our results. Analyses demonstrate that for A. 

 simplex, mean abundance is significantly different in fish 

 from unit 2 collected in winter and those from the Gulf of 

 St. Lawrence (unit 1) collected in summer (bootstrap ad- 

 justed P<0.05), but no difference could be shown between 

 those collected in winter versus summer from unit 2, nor 

 between those collected in the summer compared to winter 

 within the Cabot Strait-Laurentian Channel (Table 5). 



Discussion 



Criteria for the use of parasites as biological markers 

 of fish populations have been reviewed by Williams et 

 al. (1992). In this study, we employed the following four 

 criteria for biological markers: geographic variation in 

 prevalence or abundance, longevity of infection, absence 

 of reproduction directly in or on the host, and ease of 

 detection and enumeration. First, geographic variation 

 in prevalence and abundance was observed in the various 

 parasites. Second, the parasites or their remains have a 



