FISHERY BULLETIN: VOL. 80, NO. 2 



Growth Curve Compared with 

 Other Field Studies 



Direct observations of herring egg beds by div- 

 ers were made on Jeffreys Ledge, Gulf of Maine, 

 in 1974 by Cooper et al. (footnote 3). Spawning 

 occurred between 29 September and 3 October 

 1974 at about 35-50 m depth when the bottom 

 water temperature was 9.6°C. Larval hatching 

 began on this site on 6 October and was com- 

 pleted by 11 October, a 5-d period. Careful visual 

 examination of the egg bed by the divers sug- 

 gested that major hatching began on 7-8 Octo- 

 ber. Newly hatched larvae collected on the egg 

 bed have already been reported in Table 3 to 

 have a mean Formalin-preserved length of 5.7 

 mm (0.5 mm SD). A special 24-h vertical series of 

 plankton hauls was made slightly downstream of 

 the egg bed 11-12 October (Delaware 7/74-12). 

 The mean Formalin-preserved length of all lar- 

 vae collected by day and night hauls was 6.7 mm 

 (0.6 mm SD) (Lough and Cohen 10 ). Approxi- 

 mately 4 d transpired between the middates of 

 maximum hatching and their collection by the 

 24-h vertical study yielding an average growth 

 rate of 0.25 mm/d. According to the fitted Gom- 

 pertz growth curve (Table 4), 4-d-old larvae are 

 estimated to have reached a mean length of 6.7 

 mm at a mean growth rate of 0.26 mm/d (range: 

 0.25-0.27 mm/d) which are essentially the same 

 as the field estimates. 



Graham and Chenoweth (1973) made direct 

 observations of larval herring over egg beds on 

 northeastern Georges Bank during autumn 

 1973. Submersible observations indicated that 

 hatching occurred between 25 September and 5 

 October, a 10-d period. Larvae hatched in sea- 

 water from eggs brought on shipboard 27 Sep- 

 tember varied in length from 5 to 7 mm with over 

 90% at 6 mm. On 1 October, larvae collected 

 within the vicinity of the egg beds varied from 5 

 to 9 mm in length but the mean was 7.1 mm about 

 4 d from hatching (27 September-1 October). 

 Growth rate of these recently hatched larvae 

 over the 4 d was estimated to be 0.28 mm/d, 

 which is slightly higher but still comparable 

 with the fitted growth curve. 



Growth of larval herring based on the Gom- 



I0 Lough, R. G., and R. E. Cohen. 1982. Vertical distribu- 

 tion of recently-hatched herring larvae and associated zoo- 

 plankton on Jeffreys Ledge and Georges Bank, October 1974. 

 Lab. Ref. 82-10. Northeast Fisheries Center Woods Hole 

 Laboratory, National Marine Fisheries Service, NOAA, 

 Woods Hole, MA 02543. 



pertz curve was 0.25 mm/d at hatch, increased to 

 0.30 mm/d at 20 d, and declined thereafter to 

 <0.15 mm/d after 75 d. The average growth rate 

 over 150 d from hatch was 0.20 mm/d which is 

 similar to average seasonal estimates found in 

 most other studies of herring larvae. By follow- 

 ing length-frequency modes for Georges Bank- 

 Nantucket Shoals herring larvae collected on the 

 1971-78 ICNAF surveys, Lough etal. (footnote 4) 

 found an average rate of 0.195 mm/d as the best 

 compromise to describe average growth over the 

 7-30 mm size classes (163 d). Boyar et al. (1973) 

 estimated larval herring growth in the Georges 

 Bank-Gulf of Maine region, September-June, to 

 average 0.17 mm/d with a range of 0.14-0.25 

 mm/d. The form of the growth curve appears to 

 be universal for herring larvae with a cessation 

 in growth most noticeable during mid-larval life 

 before increasing rapidly again at the time of 

 metamorphosis. When Sette (1943) replotted the 

 Clyde Sea, spring-spawned larval herring data 

 of Marshall et al. (1937), he concluded that two 

 logarithmic curves provided a better description 

 of growth with a decrease in slope at a length of 

 19.5 mm. Graham et al. (1972) also showed a de- 

 crease in growth after about 20 mm for autumn- 

 spawned herring larvae along the coastal west- 

 ern Gulf of Maine. Townsend and Graham (1981) 

 followed two groups of larvae that entered the 

 Sheepscot River estuary of Maine that grew 

 about 0.2-0.3 mm/d from October to early Janu- 

 ary and from late February to early March, but 

 experienced similar cessation of growth from 

 late January to early February. Das (1968, 1972) 

 followed length modes of Bay of Fundy-Gulf of 

 Maine area herring larvae from hatching in Sep- 

 tember and estimated growth rates to be 0.29 

 mm/d in the autumn, gradually declining to 

 <0.14 mm/d during late autumn and winter 

 months, and then increasing geometrically to 

 >0.36 mm/d in the spring and early summer. 

 Messieh and Moore (footnote 9) also reported a 

 rapid increase in growth at metamorphosis for 

 herring larvae collected in the Gulf of St. Law- 

 rence. 



DISCUSSION 



The available data indicate that the age and 

 growth of herring larvae in the Gulf of Maine- 

 Georges Bank region can be accurately esti- 

 mated from otolith microstructure, although we 

 have no direct evidence of the increment-day 

 relation. A Gompertz growth curve fitted to the 



196 



