Boothroyd and Ennis: Reproduction iri Homarus amencanus transplanted northward 



661 



and the extent of pleopod cement gland development 

 (Aiken and Waddy 1982) were determined. In 1989 and 

 1990, pleopod setal development (Aiken 1973) was 

 determined for 47 nonovigerous females and 93 males. 

 Eighty-four ovigerous females were included among 

 the 392 females sampled over the 6 years. Egg 

 numbers were determined for nine collected in Indian 

 Arm in 1987 and 1988. Five of these were small egg 

 masses that were counted directly, the other four were 

 estimated by drying and weighing the entire mass, then 

 weighing and counting a subsample representing about 

 10% of the total. Yolk content of eggs (to the nearest 

 tenth, i.e., 0.1) was determined for 17 ovigerous 

 females carrying old, eyed eggs collected from 1986 

 to 1991. Perkins Eye Indices (PEI), which provide a 

 measure of embryonic development (Perkins 1972), 

 were determined for four of the latter. 



From July 1986 to September 1988, a continuously 

 recording thermogi'aph was maintained in St. Michael's 

 Bay at 7 m within the depth range occupied by the 

 transplanted lobsters. Mean daily temperature was ob- 

 tained from the tapes. These were averaged for the 

 first and second half of each month, with data for the 

 different years combined. Temperature during most of 

 June each year was not obtained because the recording 

 tape expired in 1987 and the instrument malfunctioned 

 in 1988. The June portion of the annual temperature 

 regime was approximated by extrapolating from tem- 

 peratures which were rising in a near-linear fashion 

 before and after. 



Results 



Changes in size composition 



Indian Arm Mean CL of all the lobsters transplanted 

 to St. Michael's Bay in the summer of 1982 was 89.1 

 mm (range 81-1 14 mm, N 987) for males and 88.9 mm 

 (range 81-1 12 mm, A^ 1001) for females (Fig. 2). We 

 assume that these are also representative of the 

 lobsters released at the Indian Arm site. When first 

 sampled in the summer of 1986, mean CL of lobsters 

 in Indian Arm had increased significantly (Tukey test; 

 P<0.001) to 107.2mm for males (A^ 87) and 97.5mm 

 for females (N 109). There were further shifts to larger 

 sizes each year, especially among males, and in the 

 summer of 1990, mean CL was significantly larger 

 (P<0.001) than in all previous years at 132.5mm (range 

 116-153mm, N 17) for males and 109.6mm (range 

 98-116mm, A^ 22) for females. 



Goose Island Mean CL of all the lobsters trans- 

 planted to St. Michael's Bay in the summer of 1985 was 

 84.1mm (range 81-95mm, N 687) for males and 84.4 

 mm (range 81-92 mm, N 811) for females (Fig. 3), 



MAIIS 



JiL. 



i>=?B7 

 1=89.1 



FEMALIS 



Jh 



1982 



11=1X1 



^jIUii 



ii=!7 

 r-Wl 



Jl 



1987 

 ipIO 

 1=1110 



JIL 



tf=32 

 i=ll*i 



130 140 150 



80 90 IW 



120 130 1« 150 



CARAPACE l£NGTH (mm) 



Figure 2 



Size-frequencies for all male and female lobsters Homarus 

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

 1982, and when sampled at the Indian Arm release site, 

 1986-90. 



significantly smaller (^test; P< 0.001) than for those 

 transplanted in 1982. We assume that these means are 

 representative of the lobsters released at Goose I. At 

 Goose I., annual shifts to larger sizes were small until 

 1988, when mean CL had increased significantly 

 (Tukey test; P< 0.001) to 96.4 mm for males (N 16) and 

 92.6mm for females (N 38). By summer 1990, mean 

 CL had increased significantly again (P< 0.001) to 

 105.6mm (range 90-131 mm, N 23) for males and to 

 95.9mm (range 89-105mm, N 22) for females. 



Incidence of new-shiell lobsters 



The donor population at Comfort Cove is subjected to 

 a very intensive fishery each spring which removes 

 most of the commercial lobsters (nonovigerous and 

 >81mmCL). Following the summer molting period, 

 the vast majority of commercial-size animals in the 

 population had molted and grown from smaller sizes 



