FISHERY BULLETIN: VOL. 71, NO. 1 



study areas attain maturity at smaller sizes 

 (507r mature between 70- to 80-mm carapace 

 length) than Maine females as indicated by 

 results of this present study; thus, I believe 

 this explains why Canadian lobsters exhibited 

 a differential growth rate between sexes, while 

 Maine lobsters (our samples were markedly de- 

 ficient of mature females) appeared to grow at 

 the same rate regardless of sex. 



MOLTING 



Lobsters were classified as shedders (recently 

 molted) when their carapace and/or chelipeds 

 were soft to the touch (lacked normal rigidity). 

 Because molting was observed to be concurrent 

 for males and females, shedding data were com- 

 bined for sexes (Table 1) . While a few lobsters 

 were observed to molt in spring, shedding did 

 not reach a peak until September in 1968 and 

 August in 1969 and 1970. 



Table 1. — Percentage of soft-shelled lobsters in monthly 

 samples from Boothbay Harbor, 1968 through 1970. 



' No sample collected. 



LENGTH-WEIGHT RELATIONSHIP 



The regression of total wet weight on cara- 

 pace length was calculated for 454 lobsters (206 

 males and 248 females) collected from April 

 1968 through March 1969. The equation used 

 was W = aU", where W = wet weight in grams, 

 L = carapace length in millimeters, and a and h 

 are constants. The regression was fitted by the 

 method of least squares using the logarithmic 

 transformation \og\oW = logioa + b logioL. 



Analysis of covariance on the regression co- 

 efficients as described by Steel and Torrie (1960) 



revealed no significant difference between sexes, 

 so data from all lobsters were combined. The 

 calculated regression equation was log W = 

 —2.9052 + 2.9013 log L. This mathematical 

 relationship is represented by the curve in Fig- 

 ure 4. 



700- 



600 



500 



400 



300- 



200- 



100 



50 



60 



5 TO 5 eo 5 



CflRARftCE LENGTH , MM 



90 



Figure 4. — Calculated length-weight relationship for 

 454 lobsters from Boothbay Harbor. The regression 

 equation is log W = -2.9052 + 2.9013 log L, 



SIZE COMPOSITION OF CATCH 



I compiled length-frequency histograms of 

 lobsters collected with wire traps in 1968, 1969, 

 and 1970 (Figure 5) . The effects of availability 

 (term encompassing both vulnerability and ac- 

 cessibility) and the high rate of exploitation by 

 the commercial fishery on our annual catches are 

 manifested by the histograms. 



The stepwise increase in numbers of lobsters 

 with size up to approximately 70-mm carapace 

 length led me to assume that this mode repre- 

 sented the size at which lobsters were fully vul- 

 nerable to our gear. Reduced vulnerability of 

 lobsters smaller than 70-mm carapace length in 

 our samples might best be attributed to the ef- 

 fects of gear selectivity and, possibly, the more 

 seclusive behavior of small lobsters. In ec- 

 ological studies of the lobster being conducted 



168 



