FISHERY BULLETIN: VOL. 70, NO. 2 



SHEEPSCOT 



^ 20 



64 65 66 67 68 69 

 YEAR CLASS 



Figure 12. — A comparison among year classes of winter 

 mortality of larvae in the Sheepscot estuary (upper 

 panel), the decline in condition of larvae in the Booth- 

 bay area (center panel), and the subsequent spring 

 catch rates in the Sheepscot (lower panel). 



sources, and the resulting changes in their dis- 

 tributions have received attention from other 

 investigators. 



Spawning grounds of herring were located in 

 the past by surveying the distribution of recently 

 hatched larvae (Tibbo et al., 1958), and more 

 recently by collecting eggs off the spawning 

 grounds (Noskov and Zinkevich, 1967). Migra- 

 tions of larvae from these grounds were traced 

 by assuming that they were transported simi- 

 larly to a particle of water. Thus, their paths 



of migration from the grounds were located with- 

 in the residual currents at the surface. Boyar 

 et al. (1971) reviewed such evidence for the 

 Georges Bank-Gulf of Maine area and decided 

 that larvae may enter the eastern sector of our 

 sampling area from the spawning grounds off 

 southwestern Nova Scotia, and that some larvae 

 from Nova Scotia may be carried along the coast 

 of Maine as far as Cape Cod, Mass. In a con- 

 current paper, lies (1971) reported on the dis- 

 persion of larvae from southwest Nova Scotia 

 and concluded from his data that the larvae were 

 transported into the Bay of Fundy where they 

 were retained during the winter. Boyar et al. 

 (1971) also suggested that larvae entered the 

 western sector of our coast from Jeffreys Ledge, 

 Cashes Ledge, Stellwagen Bank, and other 

 areas collectively just offshore of the coastal sec- 

 tor. 



The larvae from these two sources, Nova Sco- 

 tia and the ledges and banks in the southwestern 

 Gulf of Maine, possibly contributed to the coastal 

 larval population in the spring. Such a contri- 

 bution would partially explain the high catch 

 rates obtained in the Boothbay area where larvae 

 accumulated in the autumn and spring. The 

 autumnal movements of larvae into the area sub- 

 sided by early December. The catch in the area 

 at that time was less than the peak catch ob- 

 tained in the subsequent spring, indicating that 

 larvae present in autumn could not account for 

 all of the larvae found in the same area in the 

 spring. Much of the spring catch, therefore, 

 may be formed by emigrants. Das (1968, see 

 footnote 2) also discovered a similar emigration 

 by examining length-frequency distributions of 

 larvae in the coastal area of southwest Nova 

 Scotia. And Sameoto (1971)^ reached a similar 

 conclusion from catches of larval herring enter- 

 ing St. Margaret Bay on the southeastern coast 

 of Nova Scotia. 



Another explanation for the differences in the 

 early winter and the spring catches in our sam- 



* Sameoto, D. D. 1971. The distribution of herring 

 (Clupea harengus L.) larvae along the southern coast 

 of Nova Scotia with some observations on the ecology 

 of herring larvae and the biomass of macrozooplankton 

 on the Scotian Shelf. Fish. Res. Board Can., Tech. Rep. 

 252, 72 p. 



318 



