DUTIL AND COUTU: EARLY LIFE OF ATLANTIC SALMON 



62 mm stretched mesh nets (range 57-70 mm); 

 mesh size is regulated. The nets used in 1983, 

 1984, and 1985, had 5 sections of increasing 

 stretched mesh sizes: 50.8, 57.2, 63.5, 69.9, and 

 76.2 mm. Catches were recorded for individual 

 mesh sizes in 1983 combining the 4 stations. 

 Modal length increased only slightly as mesh size 

 increased. Furthermore, the distribution for the 

 69.9 mm mesh was skewed to the right, indicat- 

 ing no larger sized postsmolts were present. 

 There was also no catch in the 50.8 mm mesh, but 

 this may have been because of the small mesh 

 section being made of a coarser material in 1983. 

 Postsmolts were frequent in = 49) in the 57.2 mm 

 mesh, but the distribution for this mesh does not 

 suggest the existence of smaller postsmolts as the 

 size range is similar to that of the 63.5 mm mesh 

 and covers the size range for the 5 meshes com- 

 bined. Catches declined from a maximum in the 

 63.5 mm mesh (56) to 40 and 9 in the 69.9 and 

 76.2 mm mesh, respectively. Therefore it is un- 

 likely that there was any bias except perhaps 

 against smaller postsmolts. 



Fall Movement out of Coastal 

 Reaches 



Postsmolts gradually left the nearshore area in 

 late-September. Fishermen in 1982 started col- 

 lecting postsmolts in mid-August. Their bycatch 

 declined from mid-September and was low in Oc- 

 tober. The catch declined partly because most 

 commercial fishermen were asked to return no 

 more than 20 salmon each, and they reached this 

 limit early (Table 7). Fishing was initiated later 

 in 1983 and took place over a shorter period (23 

 September-11 October), but a 68^ decline in the 

 catch was observed between the period 29 Sep- 

 tember-5 October and the period 5-11 October. 

 Finally in 1984, postsmolts came near the coast 

 near the end of August and moved out in mid- 

 September (Table 8) so that no salmon were 

 caught in the period 20 September-20 October. 



This movement out of the nearshore zone was 

 associated with decreasing near-surface tempera- 

 tures in autumn. Temperatures measured near 

 the surface closely followed the mean air temper- 

 atures recorded in Sept-Iles (Fig. 5). Since most 

 postsmolts travelled near the surface, mean air 

 temperatures were assumed to reflect prevailing 

 conditions for postsmolts. In 1982, postsmolts 

 were abundant until mean air temperatures de- 

 clined below 5°C, i.e., in early October. The situa- 

 tion was similar in 3 stations out of 4 in 1983, 



particularly in the Bay of Matamek River near 

 Sept-Iles and in Riviere Pentecote, 2 stations 

 closer to our monitoring station. In 1984, this de- 

 cline in mean air temperature occurred earlier 

 (26 September), but surface temperatures were 

 also lower than air temperatures, and the catch 

 declined (Table 8) as soon as surface tempera- 

 tures fell below 5°C (mid-September.) Hence, low 

 temperatures were associated with a movement 

 of postsmolts out of the nearshore zone. However, 

 the reverse is not true: results for 1983 and 1984 

 suggest that postsmolts do not necessarily move 

 towards nearshore zones when prevailing tem- 

 perature conditions are favorable. 



Variations in seasonal abundance are masked 

 by a general decline in salmon abundance near 

 shore from 1982 to 1985. Fishing effort could not 

 be assessed in 1982, but the incidence of 

 postsmolts in coastal herring nets in 1982 was 

 such that it can reasonably be concluded they 

 were more abundant than in 1983, 1984, or 1985. 

 Relative abundance can be assessed for 1983, 

 1984, and 1985. Bale Trinite and Port Cartier 

 stations were operated in 1983 and 1984 using 

 similar nets at the same locations each year and 

 showed that postsmolts were more abundant in 

 1983 than in 1984 (Table 9). Finally, a station 

 was monitored near Sept-Iles in 1985 in an area 

 where the best catches were made in 1982, using 



Table 7. — Time distribution of the commercial 

 bycatch of Atlantic salmon postsmolts in 1982. 



Period 



Number 



10-31 August 

 01-15 September 

 16-30 September 

 01-15 October 

 16-31 October 



210 



118 



21 



24 



8 



Table 8. — Catch of Atlantic salmon postsmolts by 

 period and locality in 1984. 



205 



