664 



Fishery Bulletin 90(4), 1992 



The percentages of females that were ovigerous with 

 new eggs (i.e., extruded within the preceding 2 or 3 

 weeks) ranged from 4% in 1987 to 50% in 1990 in the 

 Indian Arm samples, and increased from 10% in 1989 

 to 32% in 1990 in the Goose I. samples (Table 6). Of 

 64 ovigerous females included in the combined 1987-91 

 samples, 73% had new eggs and, overall, there was a 

 substantially higher incidence of ovigerous females 

 among St. Michael's Bay lobsters in 1989-91 than 

 previously. 



The low incidence of ovigerous females in samples 

 up to 1988 indicates most of the nonovigerous females, 

 all of which had ripe ovaries in summer, failed to ex- 

 trude eggs. In subsequent years, however, the propor- 

 tion of nonovigerous females extruding increased 

 substantially. There was no evidence of hatching of old 

 eggs prior to our sampling each summer, which might 

 have accounted for the scarcity of old-egged relative 

 to new-egged females. This indicates that many 

 females that extruded lost their entire clutch of eggs 

 sometime prior to the following summer. 



Fecundity and egg development 



Egg numbers were determined for 9 ovigerous females 

 included in the 1987 and 1988 samples from Indian 

 Arm. Four of these egg counts were <0.1% of expected 

 numbers as determined from a size-fecundity relation- 

 ship for a population on the south coast of New- 

 foundland, one had 2%, and the others had 30-105% 

 of the expected number of eggs (Table 7). The extreme- 

 ly low numbers in 5 of the 9 specimens cannot be at- 

 tributed to high variability generally associated with 

 such data, but rather indicate a high incidence of 

 massive egg loss. Although egg numbers were not 

 determined for any of 21 ovigerous females included 



Table 7 



Egg numbers for nine ovigerous female lobsters Homarus 

 americanus transplanted to St. Michael's Bay, Labrador, in- 

 cluded in 1987 and 1988 samples from Indian Arm. 



* Expected number of eggs was calculated from a CL-feeun- 

 dity relationship (log,,, F = 3.0984 log,,, CL - 1.8963) for 

 a population in Placentia Bay on the south coast of New- 

 foundland (Ennis 1981). 



in the 1989 and 1990 samples, cursory examination 

 indicated that most had what appeared to be full 

 clutches, although one had just a few hundred eggs. 

 The extent of embryonic development for 17 ovi- 

 gerous females with old, eyed eggs collected from 1986 

 to 1991 ranged from 0.8 to 0.3 yolk content (Table 8). 

 Only 6 had less than half the yolk remaining when ex- 

 amined. Perkins Eye Indices (PEI) were determined 

 for four specimens. One with 0.3 yolk content had a 

 mean PEI of 470 on 29 June 1988. At an assumed con- 

 stant developmental temperature of 10°C, it was 

 estimated, using Perkin's (1972) formula, that hatching 

 would have occurred by 4 August. Another with 0.4 

 yolk content had a mean PEI of 431 on 1 August 1986, 

 for which hatching by 21 September was estimated. 



