EGG LOSS DURING INCUBATION FROM OFFSHORE 

 NORTHERN LOBSTERS (DECAPODA: HOMARIDAE) 



Herbert C. Perkins' 



ABSTRACT 



Egg loss during incubation from offshore northern lobsters, Homarus americanus Milne Edwards, was 

 estimated by counting the eggs of 196 females. The lobsters were captured along the continental shelf 

 off southern New England during October (eggs recently extruded), April, and June (eggs nearly 

 ready to hatch). Egg loss during the period October to June averaged 36% for females of all sizes 

 studied. 



The exploitation of northern lobsters in the off- 

 shore canyons of the continental shelf is steadily 

 increasing (Skud, 1969). Owing to this in- 

 creased effort, the National Marine Fisheries 

 Service (formerly the Bureau of Commercial 

 Fisheries) has initiated a study of the biology 

 and population dynamics of the stock. As ac- 

 curate estimates of fecundity are useful for 

 studying population dynamics, the present study 

 was undertaken to determine the extent of egg 

 loss from female Homarus ame7'iccu)us during 

 embryonic development and the consequential 

 magnitude of error in estimating fecundity if 

 any loss occurs. Brunei (1962, 1963) has shown 

 that female sjiider crabs, Chionoectes opilio, may 

 lose over half their eggs during the incubation 

 period. The present paper shows the extent 

 of egg loss from the northern lobster and the 

 difference in fecundity estimates depending on 

 the time during the development period when 

 the eggs are counted. 



according to carapace length. The mean num- 

 ber of eggs and the range for each 5-mm group 

 are recorded in Table 1. Carapace length was 

 measured from the posterior edge of an eye 

 socket to the distal edge of the carapace. 



The females were frozen at sea, later thawed 

 in the laboratory and their eggs removed from 

 the pleopods by stripping with small forceps. 

 The eggs were hardened in Formalin for 24 hr, 

 then soaked in fresh water before being dried 

 in an oven at 150° C. Drying time lasted 1 to 2 

 hr depending on the size of the egg mass. After 

 drying, the individual egg masses were rubbed 

 over a 1-mm screen to break up any clusters and 

 eliminate non-egg material, then counted with 

 an electronic counter (Boyar and Clifford, 

 1967). Test runs with the counter produced 

 a maximum error of ± 29^r. The counts given 

 represent numbers of viable eggs only (non- 

 viable eggs are rarely observed in masses of 

 developing eggs). 



METHODS AND MATERIALS 



The lobsters were captured with otter trawls 

 during research and commercial cruises at Hud- 

 son, Veatch, Oceanographer, Lydonia, and Cor- 

 sair Canyons. These canyons are located along 

 the edge of the continental shelf, south and east 

 of New England. The 196 female lobsters used 

 in this study were divided into 5-mm groups 



' National Marine Fisheries Service Biological Lab- 

 oratory, West Boothbay Harbor, Maine 04575. 



Manuscript received January 1971. 



FISHERY BULLETIN: VOL. 69, NO. 2, 1971. 



RESULTS AND DISCUSSION 



A curvilinear relationship was apparent when 

 the number of eggs was plotted on the corres- 

 ponding carapace length. The same result was 

 noted by Saila, Flowers, and Hughes (1969). 

 In order to employ covariance analyses in this 

 study, the data were transformed to natural 

 logarithms. The lines presented in Figure 1 

 were plotted from the antilogarithms of the val- 

 ues calculated from the linear regression equa- 

 tions (Table 2). 



451 



