GRAHAM, CHENOWETH, and DAVIS: LARVAL HERRING 



Table 1. — Methods of sampling larval herring in the western Gulf of Maine, 1962-67. Volume sampled in 7'/2-min 



tow = given volume -^ 4. 



Area 



Stations 



Season 



Gear 

 type 



Tow 



Depth 



Duration 



Water 

 strained 



Towing 

 velocity 



Coastal 



21-43 



Autumn 

 Winter-spring 



Gulf 111 



Boothbay 

 Depressor 

 trawl 



No. 1 



No. 2 



No. 4 



0-10-20 



0-10-20 

 0-10-20 

 0-10-20 



30 



30 (or 71/2) 



30 



30 (or 7'/2) 



200 



4,200(1,050) 

 17,000 

 8,000 (2,000) 



knots 

 6 



6 



4'/2 



5 



Inshore 



Autumn 

 Winter-spring 



Gulf III 



Boothbay 

 Depressor 

 trawl 



No. 1 



0-mid-depth- 

 bottom 



0-mid-depth- 

 bottom 



30 



30 



135 



12,800-4,200 



41/2 



' Dependent on mouth opening of liner. 



tained were adjusted to the number of larvae 

 captured per 100 m^ of water strained during 

 a tow. During the coastal cruises the gear was 

 towed obliquely for 30 min at each station (10 

 min each at the surface, at 10 m, and at 20 m) 

 except on the coastal cruises after autumn 1966, 

 when each of the 46 quarters was sampled with 

 two oblique ly^-min tows (21/2 "lin ^t the sur- 

 face, at 10 m, and at 20 m). The direction of 

 these two tows was selected randomly and 

 catches were averaged to obtain an estimate of 

 abundance. Filtration efficiencies of the sam- 

 pling gear approached 100%. Comparisons be- 

 tween catch rates of the Gulf III and the Booth- 

 bay Depressor trawl differed on individual sta- 

 tions during tests covering the period of their 

 exchange within the sampling program. How- 

 ever, the catch rates were similar for the two 

 gear when they were averaged for stations or for 

 an entire cruise. Experiments also showed dif- 

 ferences in catch rates between short and long 

 tows, between tows of different depths, and be- 

 tween tows made during nighttime and daytime. 

 Only the differences between rates during night- 

 time and daytime were sufficiently important 

 to the analyses of this report and they are given. 

 Information on the length and depth of tow and 

 comparisons of catch rates between the two gear 

 are being prepared for publication. 



Larval herring, preserved in 10% Formalin, 

 were measured from the tip of the jaw to the 



end of the caudal peduncle (standard length). 

 Conversion of this measurement (SL) extended 

 to total length (tip of jaw to the tip of the longest 

 lobe of the caudal fin) (TL) may be made for 

 larvae from 20 to 45 mm SL by: 



TL = — 3.47 + 1.24 SL 



RESULTS 

 HATCHING 



Catches of recently hatched herring (4-9 mm) 

 provide evidence that there are several spawning 

 areas along the western coast of the Gulf of 

 Maine, but that the time of hatching differs be- 

 tween the eastern and western sectors of the 

 coast. Recently hatched larvae were captured 

 throughout the coastal sampling area from late 

 September until early November.  Some of these 

 larvae had yolk sacs, especially those obtained 

 near the headlands of the Boothbay area, where 

 the occurrence of hatching was monitored each 

 year. Relatively large numbers of larvae were 

 captured east of Cape Small in the early autumn 

 and to the west of this Cape in late autumn (Ta- 

 ble 2) . The autumnal hatch along the coast was 

 expected, since Boyar (1968) found that the go- 

 nads of most adult coastal herring reached 

 spawning condition by late September in this 

 area. Also Goode (1884) and Bigelow and Welsh 



309 



