386 



Fishery Bulletin 98(2) 



and would correspond to the seasonal peak in larval 

 extrusion as indicated by the maturity cycle of adults 

 (Ni and Templeman, 1985; St-Pierre and de Lafon- 

 taine, 1995). On the western side of Anticosti Island, 

 the highest larval abundance is associated with a 

 cyclonic residual circulation (El-Sabh, 1976) as found 

 in previous studies (de Lafontaine, 1990; de Lafon- 

 taine et al., 1991). Our data suggest however, that in 

 1991 and 1992 the contribution of the western sector 

 to the entire redfish larval production of the Gulf 

 of St. Lawrence was small and less important than 

 that of the eastern sector. The western sector contri- 

 buted approximately up to 10.2'7( of the S. mentella 

 {MDH*A1A1 +MDH''A1A2) and up to 34.47^ of the 

 S. fasciatus larvae in the 1991 samples. This obser- 

 vation is in agreement with the estimated lower 

 biomass of adult redfish in the western Gulf of St. 

 Lawrence in relation to the eastern sector (Atkin- 

 son, 1984; Morin and Bernier^). The proportionally 

 higher contribution of S. fasciatus in the western 

 sector would be indicative of slightly higher abun- 

 dance of S. fasciatus periodically observed in that 

 part of the Gulf ( Morin^ ). 



The different geographic distributions of the various 

 larval genotypes strongly suggest differences in the 

 preferred extrusion sites of S. fasciatus and S. men- 

 tella (Figs. 3 and 4). Sebastes mentella seems to 

 prefer zones located in the central and deeper parts 

 of the channels whereas S. fasciatus preferably uses 

 shallower zones near the shelf break and along the 

 sides of the channels. This observation is consistent 

 with the reported summer distribution patterns of 

 adult redfish in the Gulf of St. Lawrence (Rubec et al. 

 1991; St-Pierre and de Lafontaine, 1995). The appa- 

 rent low proportion of S. fasciatus in the southern 

 part of the Gulf may be due to the relative lack 

 of shallower stations. Attempts to infer more preci- 

 sely the locations of extrusion sites from the obser- 

 ved larval distributions would, however, require that 

 the size frequency of sampled larvae be considered. 

 In this case, size at extrusion would therefore be 

 the best basis from which to infer the vicinity of 

 the extrusion sites. The size at extrusion for redfish 

 larvae in the Gulf of St. Lawrence is unknown. 

 Penney and Evans ( 1985 ) indicated that newly extru- 

 ded redfish (presumably S. mentella — see Penney, 

 1987' larvae from Flemish Cap (east of Newfoun- 



2 Morin, B., and B. Bernier. 1997. The status of redfish in Unit 

 1 (Gulf of St. Lawrence). Can. Stock Assess. See. Res. Doc. 

 97/112, 23 p. Sciences Branch, Department of Fisheries and 

 Oceans, Maurice Lamontagne Institute, 850 Route de la Mer, 

 Mont-Joli, Quebec, Canada CSH 3Z4. 



■■' Morin, B. 1998. Unpubl. results. Sciences Branch, Depart- 

 ment of Fisheries and Oceans, Maurice Lamontagne Institute. 

 850 Route de la Mer, .Mont-Joli, Quebec. Canada G5H 3Z4. 



dland Grand banks) ranged between 6.2 and 8.9 mm. 

 From the age-length relationships, these authors 

 estimated that the mean size of newly extruded 

 lai-vae was 7.68 and 8.23 mm in two consecutive 

 years. Magnusson and Magnusson"* also reported con- 

 siderable variation in the size at extrusion (5.5-7.2 

 mm) of redfish larvae from the Northeast Atlantic 

 waters. Penney (1985) indicated that the mean size 

 of pre-extruded larvae in gravid females of S. fascia- 

 tus and S. mentella collected in southern Newfoun- 

 dland waters was 7.34 and 7.89 mm, respectively. 

 The size range of larvae in our study was 5.0 to 12.3 

 mm in 1991 and 5.6 to 10.9 mm in 1992. The propor- 

 tion of larvae <8.5 mm was 467^ and 54^7^ in 1991 and 

 1992, respectively, suggesting that a large number 

 of sampled larvae were recently extruded. Assuming 

 an average size at extrusion of 7.5 mm and given 

 the estimated growth rates (0.1 to 0.15 mm/day) 

 reported in the literature (Penney and Evans, 1985; 

 Herra, 1989), the maximum length of larvae in our 

 samples would correspond to larvae of approxima- 

 tely 22 to 45 days old. The majority of larvae being 

 <10 mm long, the sampled population was certainly 

 less than 1 month old. Although the period of time 

 between larval extrusion and time of collection may 

 allow for some horizontal drift of larvae by the sur- 

 face currents, the relatively small size and the presu- 

 mably young age of the larvae would tend to indicate 

 that these larvae did not disperse much (in relation 

 to the large area sampled in our study) and would 

 have been collected close to their extrusion sites. 

 Consequently, the differences in the relative distri- 

 bution of the genotypes of larvae indicate that the 

 extrusion sites of the two species do not overlap to a 

 large extent within the Gulf of St. Lawrence. 



The mean and the range of the size of larvae varied 

 between genotypes where larvae of the MDH'^A2A2 

 were significantly smaller (by 1.5 to 2.0 mm) than 

 those of the two other genotypes (Fig. 6). This fin- 

 ding is consistent with other observations, sugges- 

 ting that the length of S. fasciatus at extrusion is 

 smaller than that of S. mentella, although conside- 

 rable variability exists (Penney, 1985; 1987; Penney 

 and Evans, 1985 ). The similar results obtained in the 

 two sampling years of our study would tend to reveal 

 a species-specific characteristic. In addition, the dif- 

 ference between the mean (and modal) size of each 

 homozygote genotype was larger than that for the 

 reported size at extrusion between the two species 

 (0.5-0.6 mm; see Penney, 1985; Penney and Evans, 



Magniisson, J. V., and J. Magnusson. 1977. On the dis- 

 tinction between larvae of S. marinus and S. mentella: prelimi- 

 nary report. Int. Counc. Explor. Sea (ICES) Council Meeting 

 197'7/F:48. 



