FISHERY BULLETIN: VOL. 81, NO. 2 



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0.6 



0.4 



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36 31 39 23 10 1 



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• 38 36 19 4 

 24 39 



a= 1.00 + 0.034 

 b= 15.305 ±0.366 

 c= -0.248 t 0.006 



2 5 3 8 8^X 



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o 

 a. 



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B 



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27 26 16 17 1 



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3- 1.00+ 0.024 

 b= 10 751 ± 0.207 

 c= - 0.221 + 0.004 



20 



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40 



~l >" 



60 



80 



"> I - 



100 



120 



140 



Carapace Length (mm) 



FIGURE 3. — Relationship between proportion mature based on 

 gonad development and carapace width (CW) for (A) male and (B) 

 female rock crabs from the Bay of Fundy and southwestern Nova 

 Scotia. Values next to dots are numbers of crabs examined at every 

 5 mm CW class, a = asymptote, b and c = empirical constants 

 followed by the 957c nonlinear confidence intervals for the logistic 

 curve (see text for formula). 



mm C W. Most males in the 34.2-134.0 mm C W range 

 had stage-3 gonads and in the 61.9-137.8 mm CW 

 range had fully developed stage-5 gonads. The 

 smallest female with mature ovaries (stage 3) was 

 20.2 mm C W and the largest female with immature 

 ovaries (stage 2) was 72.2 mm C W. Many females had 

 stage-3 ovaries in the 39.4-99.6 mm CW range, and 

 many females had fully developed stage-5 gonads in 

 the 44.7-105 mm CW range. 



Size at 50% maturity for male rock crabs, estimated 

 as the inflection point in the CW-chela height data, 

 was 64.9 mm CW (Fig. 4A), which was similar (61.7 

 mm CW) to the estimate obtained by the gonadal in- 

 spection technique (Fig. 3A). Since only one regres- 

 sion line, using the best fit method (Somerton 

 1980a), could be obtained for the female CW-chela 

 height data (not shown in this paper), this relation- 

 ship could not be used to estimate sexual maturity in 



360 



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I I I I 1 I I I I 1 I I I I 



20 40 60 80 100 120 140 



Carapace Width (mm) 



FIGURE 4. — Maturity estimation using rock crab morphometric data 

 in relation to carapace width (CW) for (A) male chela height (Y) 

 (arrow indicates inflection point of two regression lines or 50% matu- 

 rity; r= correlation coefficient; N = number of individuals), and (B) 

 female abdomen width/carapace width ratio (dots are means, verti- 

 cal lines are ± 1 standard deviations, numbers above each dot are the 

 number of individuals measured for each 5 mm CW group). 



female rock crabs. The abdomen width/C W ratio was 

 linear for males (not shown in this paper), but cur- 

 vilinear for females (Fig. 4B), indicating that 

 broadening of the abdomen is a female secondary 

 sexual characteristic. The inflection and asymptote 

 showing onset and 100% sexual maturity, respective- 

 ly, occurred at about 37 and 77 mm CW (Fig. 4B) 

 which is similar to that derived by gonadal inspection 

 (Fig. 3B). Abdominal width and chela length (not 

 height) have been used to estimate onset of sexual 

 maturity of rock crabs by Shotton (1973) and Terret- 

 ta (1973). The abdominal width/CW ratio has not 

 been previously used for rock crabs, although com- 

 monly used for lobsters in estimating sexual maturity 

 (Templeman 1935; Aiken and Waddy 1980). The 

 results suggest that external morphological secondary 

 sexual characteristics generally coincide with physio- 

 logical maturity in C. irroratus females and males. 



The presence of external eggs on females is an ob- 

 vious indicator of functional maturity. The smallest 

 ovigerous female was 41.1 mm CW, whereas most 

 ovigerous females caught were >65 mm C W (Fig. 5), 

 which generally agrees with the maturity curves 

 based on gonad development (Fig. 3B) and ab- 



