KROUSE: SIZE OF AMERICAN LOBSTERS 



metric relationship was based on Templeman's 

 (1935) observation that the female's abdomen 

 markedly increases in width during maturation. 

 I applied Templeman's method to my data on 

 482 females from inshore Boothbay Harbor 

 (1968-71) and 31 berried Canadian lobsters 

 (1970) as well as data on 217 females from in- 

 shore Boothbay Harbor collected in 1966 by 

 Herbert C. Perkins of the National Marine Fish- 

 eries Service, West Boothbay Harbor, Maine. 

 Carapace lengths were grouped by 5-mm size 

 groups, and then abdominal widths of each size 

 group were averaged. Ratios of abdominal 

 width to carapace length were plotted against 

 carapace length, and resulting curves were fitted 

 by eye (Figure 9). Inflection points, which in- 

 dicated size where maturity began, occurred at 

 approximately 80-mm carapace length for both 

 sets of Boothbay Harbor data. For the offshore 

 population of American lobsters, Skud and Perk- 

 ins (1969) reported an inflection point of 77 mm. 

 Asymptotes, which denoted the size where all 

 lobsters were assumed to be mature, appeared 

 at about 115 mm for Perkins' Boothbay Harbor 

 data, while an asymptote was not reached for 

 my Boothbay Harbor data. I believe the asymp- 

 tote at 115 mm was probably deceptively higher 



s 

 I" 



".70 



S 



s 

 I" 



h- 

 O 



^.60 



.50 



OFFSHORE 



(SKUD a PERKINS) 



N- 1.700 



BOOTHBAY HARBOR 



(PERKINS) 



N'2I7 



BOOTHCAY HARBOR 

 (KROUSE) 



N'4e2 



30 



40 50 60 70 80 90 



CARAPACE LE^GTH, MM 



OO MO 



120 



Figure 9. — Ratio of abdominal width to carapace length 

 plotted against carapace length for Boothbay Harbor 

 female data collected by Krouse and Perkins, berried 

 Canadian female data, and Skud's and Perkins' study, 

 1969. 



because of an insufficient number of lobsters 

 sampled for sizes above 105 mm, which consti- 

 tuted less than 5'^? of the total sample. This con- 

 clusion was maintained both by Skud's and Perk- 

 ins' (1969) data that demonstrated an asymptote 

 at 100 mm and by the following section on length 

 frequencies of ovigerous females from Maine. 

 The relatively early maturity of Canadian fe- 

 males, particularly those inhabiting warm water 

 of the southern part of the Gulf of St. Lawrence 

 (Templeman, 1944) , is demonstrated in Figure 9. 

 The length-frequency distribution of berried 

 females taken along the Maine coast (Figure 10) 

 disclosed that a few females began extruding 



5 100 5 no 

 CARAPACE LENGTH, MM 



130 



Figure 10. — Length-frequency distribution of native 

 Maine berried females, 1966 through 1970. 



eggs at 83-mm carapace length while the per- 

 centage of ovigerous females gradually increased 

 to the first peak at 91 mm. The most pronounced 

 mode occurred at about 105 mm, which was con- 

 sidered to be the size when nearly all females 

 were mature. It should be mentioned that the 

 modes at 91 and 105 mm corresponded with as- 

 sumed age or molt class modes determined by 

 Thomas (1971, see footnote 3) from commercial 

 catch data. 



The length-frequency distribution of berried 

 females becomes particularly meaningful when 

 compared with percent frequencies of female 



171 



