NOTE Marcogliese et al : Use of parasites in the identification of stocks of Sebastes mentello 



187 



long life span in their hosts. Larval anisakid nematodes 

 can survive for a number of years in the fish host; McClel- 

 land and Marcogliese (1994) provided a detailed discus- 

 sion of the use of anisakid parasites as biological tags for 

 fish stocks. They pointed out that although prevalence and 

 abundance of anisakids may vary over longer time scales, 

 they are stable over the time frame (a few years) of a given 

 survey, rendering them suitable for a stock discrimination 

 study. Remarkably, of the 24 studies on biological tags 

 reviewed by Arthur (1997) between 1990 and 1997, eight 

 of them employed anisakid nematodes. Although the cope- 

 pod S. lumpi has a limited life span, the cepahlothorax 

 and scar tissue from previous infections persist for many 

 years (Templeman and Squires, 1960; Sindermann, 1961; 

 Reimer and Szuks, 1989; Bakay, 1988'). Third, none of 

 these parasites multiply directly on the host and thus aug- 



' Bakay, Y. I. 1988. Application of results from parasitological 

 investigations in redfish (Sebastes mentella Travin) popula- 



tional structure studies. 

 35, 14 p. 



Int. Coun. Explor. Sea CM. 1988/G: 



ment their abundance, as in the case of some protozoans 

 and monogeneans. The anisakids are larval stages, and 

 the copepod produces free-swimming larvae. Lastly, the 

 parasites chosen are easily detected and counted. 



We have shown that the parasite fauna of the deepwa- 

 ter redfish (S. mentella) can provide useful information on 

 stock discrimination and definition of stock boundaries, as 

 has been demonstrated for other fishes (see Williams et al. 

 1992; Arthur, 1997). Indeed, fish from all adjacent zones, 

 with the exception of the Labrador Sea and Gulf of St. 

 Lawrence, could be separated on the basis of abundance 

 of at least one species of parasite. Distinction between 

 redfish from the Gulf of St. Lawrence (unit 1) and the 

 Cabot Strait-Laurentian Channel (unit 2) is reinforced 

 by analyses demonstrating differences between the mean 

 abundance of A. simplex in fish collected from the Gulf in 

 summer and those in unit 2 in winter or summer. Further- 

 more, there w^ere no differences in abundance of A. simplex 

 detected in fish from unit 2 between winter and summer. 

 Our results also support those of previous studies that 

 demonstrated differences between redfish from the Flem- 



