McClelland and Melendy: Heminths as tags in delineating stock of Hippoglossoides platessoides 



181 



49°N  



48'N 



47°N - 



46 N - 



65 W 



64 W 



63 W 



62"W 



61 "W 



60W 



59'W 



58=W 



Figure 1 



Map of eastern Canada indicating sites where American plaice {Hippoglossoides plates- 

 soides} were sampled in the southwestern (•) and southeastern (■) Gulf of St. Lawrence, 



and on or near the Cape Breton Shelf (♦). The depth contour ( ) is at 100 m. The pale 



gray lines demarcate North Atlantic Fisheries Organization divisions (4T, 4S. 4R) and 

 subdivisions (3Pn, 3Ps, and 4Vn). 



4Vn) (Swain et al., 1998). Clay (1991), noting the abun- 

 dance of plaice in the Gulf portion of the Channel in 

 January, surmised that southern Gulf plaice, unlike 4T 

 cod, with which they are often closely associated, do not 

 migrate through the Cabot Strait to over-winter in 4Vn. 

 Length-at-age data from commercial landings indicate 

 that plaice taken near the Cabot Strait late in the year 

 are primarily from the slower growing eastern 4T (Cape 

 Breton) stock (Tallman, 1991). A few older plaice tagged 

 on Bradelle Bank, northwest of the Magdalen Islands, 

 however, have been recovered in the Cabot Strait area 

 in fall and winter (Powles, 1965). Clearly, tagging data 

 and information on seasonal distributions from research 

 surveys and commercial fisheries have provided little 

 insight into the movements of 4T plaice stocks in the 

 Laurentian Channel in winter and have not dispelled 

 the possibility that 4T stocks may be exploited during 

 the winter fishery within 4Vn. 



Parasites as biological tags have often proven advan- 

 tageous over more costly mark-recapture methods in 

 studies offish stock structure and migration (Williams 

 et al, 1992) and are useful as markers in surveys for 

 allocating quotas and combating illegal landings (Pow- 

 er et al., 2005). Parasite markers have shown potential 

 in stock delineation of numerous demersal fish species 

 (Marcogliese et al., 2003; MacKenzie and Abuanza, 



2005; Melendy et al., 2005), including flatfish species 

 such as Greenland halibut (Reinhardtius hippoglossoi- 

 des) (Arthur and Albert, 1993; Boje et al, 1997), Pacific 

 halibut (Hippoglossus stenolepis) (Blaylock et al., 2003), 

 and winter flounder (Pleiironectes americanus) (McClel- 

 land et al., 2005). Although there have been no prior 

 attempts to use parasite assemblages in describing the 

 stock structure of American plaice, parasitological sur- 

 veys of plaice in the Northwest Atlantic have identified 

 a number of potential parasite tags. Scott (1975), for 

 example, concluded that the enteric digeneans Sterin- 

 gotrema ovacutum, Zoogonoides viviparous, and Fel- 

 lodistomum furcigerum might prove useful as tags for 

 plaice stocks from the southern Gulf of St. Lawrence, 

 Scotian Shelf, and northeastern Gulf of Maine. Zub- 

 chenko (1985) remarked that species compositions and 

 infection parameters of 20 protozoan and metazoan 

 parasites of plaice from the Grand Bank, Flemish Cap, 

 and northeastern Newfoundland and Labrador are 

 peculiar to their geographic origin. Finally, studies 

 of the temporal and geographic distributions of larval 

 sealworm {Pseudoterranova decipiens) (Nematoda) in 

 Atlantic Canadian groundfish have revealed significant 

 disparities in prevalence and abundance of sealworm 

 in neighboring plaice stocks (McClelland et al., 2000; 

 McClelland and Martell, 2001b). 



