382 



Fishery Bulletin 98(2) 



52° 



Belle Isle Strait 



Quebec 



Figure 4 



Geographic distribution of the larval genotypes MDH*A1A1 characteristic of S. men- 

 tella (white), MDH*A2A2 caracteristic of S. fasciatus (black) and MDH*A1A2 (gray) in 

 1992. Sampling station numbering does not correspond with that for 1991. 



group comprised stations 26-29 and 33-34 where 

 the MDH'*A2A2 genotype is generally the most fre- 

 quent. The frequency of allele MDH'^A2 at stations 

 26-29 within the Gaspe current system along the 

 north shore of the Gaspe peninsula was very high, 

 ranging from 0.860 to 1.0. At the northernmost sta- 

 tion (33), the allele MDH*A2 predominated and the 

 frequency of both alleles was equal (0.500) at station 

 34. There was no significant deviation from Hardy- 

 Weinberg expectations at the stations of this group. 

 The second group comprised the central stations (30 

 31, 32). At theses stations, the three genotypes were 

 represented but there was an abrupt inversion of the 

 most frequent allele. At these stations, the frequency 

 of allele MDWAl ranged from 0.500 to 0.782. The 

 frequency of this allele never equaled 1.0. Significant 

 departure from Hardy- Weinberg expectations was also 

 observed at these three central stations (Table 1). 



On the eastern side of Anticosti Island, the geno- 

 type MDH*A1A1 was most frequent in a group of 

 stations located at the south-east end of the island 

 near the junction of the Laurentian and Esquiman 

 channels. The three genotypes were observed at each 

 site except for station 22, where only MDH*A1A1 

 was observed, and at station 21, where the hetero- 



zygous genotype was absent (Fig. 3; Table 1). Devia- 

 tion from Hardy-Weinberg expectation was observed 

 at stations 19 and 21 only (Table 1). The northern 

 stations (8, 9, 10, 13, 14, 15) at the north-eastern end 

 of Anticosti Island formed a distinct group where the 

 genotype MDH''A2A2 dominated. The frequency of 

 allele MDH*A2 varied from 0.417 to 1.0 (Table 1). 

 The three genotypes were observed at stations 9, 13, 



14, and 15 where significant deviation from Hardy- 

 Weinberg was observed at all but sampling station 

 15 (Table 1). 



In 1992, the genotype MDH*A1A1 was also the 

 most frequent genotype observed throughout the 

 study area, except for stations 22, 29, and 33. where 

 the genotype MDH*A2A2 was dominant ( Fig. 4 ). The 

 allele MDH'^Al was thus the most frequent except at 

 these three sampling stations (Table 2). Stations 29 

 and 33 were the northernmost stations where larvae 

 were found during our study. The frequency of the 

 genotype MDH'''A2A2 increased towards the north 

 within the sampling area although it was not the 

 most frequent genotype. This trend was also obser- 

 ved in 1991 (Fig. 3). In general, the three genotypes 

 were represented at all stations except at stations 3, 



15, 16, 27, and 33, where only one or two genotypes 



