Boothroyd and Ennis Reproduction in Homarus annericanus transplanted northward 



663 



Table 4 



Ovary color and ova diameter among nonovigerous female 

 lobsters Hoviarus americanus transplanted to St. Michael's 

 Bay, Labrador (Indian Arm in 1982, Goose I. in 1985) during 

 sampling, 1987-90. 



"The high proportion with medium-green ovaries in the 

 1987-88 sample is probably due to a different observer than 

 in 1989-90. 



■^'Includes one specimen with yellow specks throughout the 

 ovary, indicating resorption underway. 



in color, with ova 0.8-1. 5mm in diameter (Table 4). All 

 these ovaries were developing for extrusion in the 

 summer they were sampled; one had yellow specks 

 characteristic of an ovary being resorbed. However, of 

 these nonovigerous females, only 2 of 24 sampled in 

 1989 (2 out of 111 overall) had sufficient pleopod 

 cement gland development (Stage 3) to indicate egg 

 extrusion would occur (Table 5). The seminal recep- 

 tacles of all of the nonovigerous females examined from 

 1987 to 1990 were full, which means each had mated 

 at the last molt and was capable of fertilizing a clutch 

 of eggs. Pleopod setal development indicated 25% of 

 24 and 100% of 23 nonovigerous females sampled in 

 1989 and 1990, respectively, would molt (Table 3). 

 While molting does not preclude egg extrusion in the 

 same summer, this is unlikely to occur among lobsters 

 in St. Michael's Bay. This phenomenon probably in- 

 volves only animals extruding for the first time and 

 <81mmCL (Ennis 1984a). 



Incidence of ovigerous females 



The reproductive cycle in female lobsters normally 

 covers 2 years. Molting and mating occur one summer, 

 egg extrusion one year later, followed by hatching of 

 eggs, molting, and mating again in the third summer 

 (Aiken and Waddy 1980a). Departures from this 2-year 

 cycle known to occur in the wild include molting, 

 mating, and extrusion in the same summer (mentioned 

 in the preceding section) and resorption of ripe ovaries 

 just before extrusion (Aiken and Waddy 1976 and 



1980ab, Ennis 1984b). While variability in the incidence 

 of these phenomena may contribute somewhat, the in- 

 tensity of the commercial fishery and its timing in rela- 

 tion to the spawning season exert by far the greatest 

 impact on the incidence of ovigerous females in a 

 lobster population. 



At Comfort Cove, most of the nonovigerous com- 

 mercial-size females in the population are removed by 

 the spring fishery just before the summer spawning 

 period. In autumn sampling from 1986 to 1990 an 

 average 6% of commercial-size females were ovi- 

 gerous, excluding those that molted and grew from 

 subcommercial sizes and extruded as well during the 

 summer (Ennis, unpubl. data). Not being fished and 

 being more likely to spawn as well because of their 

 larger size, the percentage of females ovigerous among 

 St. Michael's Bay lobsters by comparison should be 

 quite high. 



In St. Michael's Bay, the percentages of females that 

 were ovigerous vWth old eggs each summer (i.e., ex- 

 truded previous summer) were very low, particularly 

 in 1986-88 samples, considering all nonovigerous 

 females examined the previous summer had ripe 

 ovaries. In the 1986 Indian Arm sample, 19.3% of the 

 females were ovigerous, including both new- and old- 

 egged females which were not distinguished at the 

 time. In subsequent years, the incidence of ovigerous 

 females with old eggs increased from 4.0% in 1987 to 

 33.3% in 1991 (Table 6). No ovigerous females were 

 included in Goose I. samples until 1989, when 10% of 

 the females carried old eggs. In 1990 and 1991 samples, 

 however, there were none with old eggs (Table 6). 



