FISHERY BULLETIN: VOL. 70, NO. 2 



10 



8 



UJ 



o 



< 



6 - 



NIGHT 

 N = 6,650 \ 



DAY J 



N = 2.874 



20 30 40 



LENGTH (MM) 



50 



Figure 10. — Length-frequency curves of larvae captured 

 in the Boothbay area at night and during the day. 



those larvae larger than 36 mm occurred earlier 

 in the year and their peak in abundance occurred 

 later than that of larvae captured during the day 

 ( Figure 11). In 1964, losses by avoidance began 

 in December. Failure to catch larvae began 

 later the following year (in January) because 

 the larvae that initially entered the Boothbay 

 area were smaller than those that entered in 

 1964 (Figure 7) . Catches of larvae larger than 

 36 mm in length in the Boothbay area were si- 

 milar to those obtained with buoyed and an- 

 chored nets set in the Sheepscot estuary at night 

 during 1966. This similarity indicated the ease 

 with which larvae were captured at night. The 

 buoyed nets strain water at a much lower velo- 

 city than the trawl. 



In late April larvae were occasionally observed 

 schooled in shallow coves. By late May large 

 numbers of these fish were frequently observed 

 in the shallow coves whereas the numbers cap- 

 tured at our sampling stations had declined. 

 This change in distribution was coincident with 

 the period of metamorphosis (about 41-50 mm 

 SL) from larval to juvenile form. Metamor- 



phosed herring were found in the Boothbay and 

 other inshore areas but not in the outer coastal 

 waters during the summer (Davis and Graham, 

 1970). 



Variations in the lengths of larvae in our 

 samples related to their shoreward movements, 

 avoidance of gear, and departure from our sam- 

 pling stations, caused discrepancies when esti- 

 mating the real growth of larvae in their envi- 

 ronment. Some estimate of growth rate may be 

 obtained, however, from changes in modal length 

 at certain times of the year. During 1965, the 

 modal lengths of a single abundant group of 

 larvae may be traced from the autumn into De- 

 cember. This group was not greatly influenced 

 by mixing with other groups of different sizes 

 and avoidance of our gear was not yet important. 

 From late September to early December, the 



E 

 O 

 O 



oc 



UJ 



a. 



JAN. 



FEB. 



MAR. 



APR. 



MAY 



Figure 11. — Monthly progression of larval catches (lar- 

 vae 36 mm and larger) in the Boothbay area from trawl 

 tows at night and during the day and in the upper 

 Sheepscot estuary from buoyed and anchored nets at 

 night. 



316 



