their ovaries and internal egg size. These 

 lobsters, captured in May and June 1967 from 

 Hudson, Veatch, and Oceanographer Canyons, 

 had carapace lengths of 7.6 to 10.7 cm. The 

 developmental stage of the ovary was cate- 

 gorized according to (1) color (white indicated 

 immature ovaries; yellow, maturing; and green, 

 mature) and (2) mean egg diameter (less than 

 0.4 mm. indicated an immature ovary; 0.4 to 

 0.8 mm., a maturing ovary; and larger than 

 0.8 mm., a mature ovary). Egg diameter was 

 determined from a sample of 10 eggs taken 

 from the surface of the ovary. The width and 

 length of each egg were measured, and an 

 average of the two measurements was used as 

 the "size." Lobsters with immature eggs had 

 carapace lengths of 7.6 to 8.4 cm.; females 

 with developing eggs were 7.6 to 9.1 cm.; and 

 those with mature eggs were 8.0 to 10.7 cm. 



Measurements of the width of the second 

 abdominal segment had been taken for 41 of 

 these females from Hudson, Veatch, and Ocean- 

 ographer Canyons. When the measurements of 

 the ovarian eggs of these 41 individuals were 

 plotted against the corresponding width of the 

 abdominal segment, a definite relation was 

 apparent (fig, 6). The highly significant corre- 

 lation between the egg size and the abdominal 

 width (r = 0.897, P < 0.01), and between egg 

 size and carapace length confirms the relation 

 of morphometric changes and maturity. Though 

 exceptions can be anticipated, on the basis of 

 our samples all females over 10 cm. in length 

 (carapace) and/or with an abdominal width 

 greater than 6 cm. are mature. 



WIDTH OF SECOND ABDOMINAL SEGMENT {MM.) 



Figure 6. — Relation between width of second abdominal 

 segment and size of internal eggs. 



SUMMARY 



The trawl-fishery for lobsters in the off- 

 shore waters of the North Atlantic is de- 

 scribed and the increase in landings during re- 

 cent years is discussed. This fishery con- 

 tributed less than 1 percent to the U.S. lobster 

 landings before 1948, but accounted for 17 

 percent of the total in 1968. 



Samples of lobsters were obtained during 

 research cruises and from commercial catches 

 in five fishing areas --Hudson, Veatch, Ocean- 



ographer, Lydonia, and Corsair Canyons. The 

 size composition, sex ratio, and number of 

 egg-bearing lobsters are summarized by can- 

 yon. 



Lobsters were smaller and apparently more 

 numerous in the areas of the Continental Shelf 

 west of and including Veatch Canyon than in 

 areas to the east. At several canyons the 

 average size of lobsters and the ratio of fe- 

 males to males increased with depth, and at 

 some canyons there were striking differences 

 between the numbers of lobsters caught in 

 shoal waters (100-182 m.) and those taken in 

 deep waters (over 182 m.). At Veatch Canyon, 

 more lobsters were taken in shoal waters, 

 whereas at Lydonia catches were much better 

 in deep water than in shoal areas. There were 

 also differences of day and night catches at 

 the various canyons. 



Females dominated the catch, at times ac- 

 counting for 70 percent of a sample. The ratio 

 of females to males was about 1:1 at sizes 

 below 8 cm. carapace length. From 9 to 15 

 cm. the proportion of females increased but 

 declined thereafter; at the largest sizes, 19 to 

 21 cm., males predominated. Skud (in press) 

 examined the size composition and sex ratio by 

 canyon area and hypothesized that the dif- 

 ferences were due mainly to the effects of 

 fishing. 



Molting occurred from spring through fall 

 in most areas. July appeared to be the month 

 of peak molting at Veatch Canyon, and there 

 was an indication that greatest molting activity 

 occurs later in the areas east of Veatch Can- 

 yon. 



The number of egg-bearing females in each 

 size group was tallied on the researchcruises, 

 and these data, coupled with measurements 

 of the second abdominal segments and ovarian 

 eggs, showed that maturity may be attained at 

 a carapace length of 8.0 cm. and indicated that 

 all females are mature at a carapace length 

 of 10.0 cm. or at an abdominal width (second 

 segment) greater than 6 cm. 



LITERATURE CITED 



BRUCE, ROBERT A. 



1967. North Atlantic trawl nets. U.S. Fish 

 Wildl. Serv., Fish. Leafl. 600, 23 pp. 



COL TON, JOHN B. JR., ROBERT R. MARAK, 

 SAMUEL R. NICKERSON, and RUTH STOD- 

 DARD. 



1968. Physical, chemical, and biological ob- 

 servations on the Continental Shelf, Nova 

 Scotia to Long Island, 1964-66. U.S. Fish 

 Wildl. Serv., Data Rep. 23, 189 pp. 



FIRTH, FRANK E. 



1940. Giant lobsters. New Engl. Natur. 9: 

 11-14. 

 PERKINS, HERBERT C., and BERNARD E. 

 SKUD. 

 1966. Body proportions and maturity of fe- 

 male lobsters. Amer. Zool. 6: 615. 



