FISHERY BULLETIN: VOL. 86, NO. 2 



of smolts released in spring in New England and 

 caught in summer in Canada (Meister 1984). Ru- 

 mors of bycatch in herring nets along the coast of 

 the northern Gulf of St. Lawrence in autumn pro- 

 vided an occasion to acquire some knowledge con- 

 cerning the elusive postsmolt. Production of 

 salmon in the sea may well be limited by the 

 success of smolts in the marine environment. 



Materials and Methods 



Postsmolts were collected between Bale Trinite 

 and Riviere-au-Tonnerre in the northern Gulf of 

 St. Lawrence, in 1982, 1983, 1984, and 1985 (Fig. 

 1). Fishermen contacted in summer 1982 col- 

 lected postsmolts in late summer and autumn as 

 bycatch in herring gill nets. Four of them were 

 asked in 1983 to monitor the catch of postsmolts 

 in experimental gill nets in late-September in 4 

 locations (Bale Trinite, Riviere Pentecote, Port 

 Cartier, and Sept-Iles). We also monitored sta- 

 tions in Bale Trinite in 1983 (23 September-11 

 October), in Baie Trinite and Port Cartier in 1984 

 (21 August-20 October), and in Sept-Iles in 1985 

 (20 August-4 October). Finally, smolts and early 

 postsmolts were collected in seines in June and 



July, during an eel marking program in the estu- 

 ary of Grande Trinite River at Baie Trinite (Fig. 

 1). 

 Fishermen used standard herring gill nets in 



1982, but custom-made gill nets were used in 



1983, 1984, and 1985. Custom-made gill nets had 

 5 sections of increasing mesh sizes (50.8, 57.2, 

 63.5, 69.9, and 76.2 mm stretched) covering the 

 range in mesh sizes of herring gill nets in the 

 northern Gulf of St. Lawrence. Stretched mesh 

 sizes were determined by measuring 10 meshes 

 per section. Sections were 6 m deep and 10 m long. 

 In 1983, 1984, and 1985, postsmolts were 

 recorded by section individually. In 1984 and 

 1985, their position in the nets was recorded more 

 precisely: floating lines had numbered buoys and 

 a string divided the nets into 2 halves horizon- 

 tally. Time of the catch was also recorded. The gill 

 nets were usually visited at 2-h intervals be- 

 tween 0600 and 1800, as sea conditions allowed. 

 They were left fishing overnight. Gill nets were 

 all set at the surface and near shore (<2 km). 

 Mean air temperatures for 1982 to 1985 were 

 drawn from Environment Canada meteorological 

 summaries for Sept-Iles airport. Temperature 

 recorders were also tied to nets in 1983, 1984, and 



R.MOISIE 



SEPT-ILES 

 PORT CARTIER. 



R.PENTECdTE*/ 



NORTH SHORE 



GULF 

 OF 

 ST. LAWRENCE 



Figure 1. — Locations of the areas investigated in the northern Gulf of St. 

 Lawrence (shaded area). 



198 



