FISHERY BULLETIN VOL, 77. NO 3 



overlapped. Significant differences (P = 0.05) were 

 found between the v-intercepts of either sex for 

 both the complete and partial regressions, so 

 males and females were treated separately. Plots 

 of the predictive regressions show that male Jonah 

 crabs averaged about 8% heavier than females of 

 the same CW over the range 115-130 mm (Figure 

 8). 



SUMMARY 



FromJuly 1968 through March 1978, 419 male 

 (67-168 mm CW) and 535 female (74-136 mm) 

 Jonah crabs were collected from research traps 

 and commercial fishermen. Even though male 

 Jonah crabs attain larger sizes (mean sample 

 113.7-141.1 mm CW) than females (mean sample 



104.8-114.0 mm), many female Jonah crabs are 

 harvested commercially whereas, rock crab land- 

 ings are chiefly composed of males. 



No Jonah crabs <67 mm CW were caught and 

 only 2.79^ of the total catch were <90 mm CW. 

 This with other evidence indicates that small 

 Jonah crabs inhabit greater depths (>20 m) than 

 those sampled. 



Catch per unit of effort values for Jonah crabs 

 caught with research gear generally increased 

 during summer, peaked in fall, and then declined 

 sharply. Fluctuations in the catch were attributed 

 primarily to movement. Catches were highest at 

 the deeper, more seaward sampling sites where 

 the substrate was predominantly rocky. In con- 

 trast, rock crabs were more abundant at those 

 relatively shallow estuarine stations having soft 



BOOr 



550- 



500 



X X 



Figure 8.— Carapace width-weight rela- 

 tionships calculated for 110 male and 90 

 female Jonah crabs from the Boothbay 

 Harbor region. Standard errors of the re- 

 gression coefficients are 0,1793 (a) and 

 0.0850 (b) for males and 0,2023 (a) and 

 0.0984 (6) for females. 



95 100 105 110 115 120 125 130 135 140 145 150 155 

 CARAPACE WIDTH (MM) 



692 



