Peemoeller and Stevens: Age, size, and sexual maturity of Busycotypus cana/iculatus in Buzzards Bay, Massachusetts 
271 
Table 1 
Number and proportion of each sex by interval of shell length (SL) for 
channeled whelk ( Busycotypus canaliculatus ) collected in August 2010 
and July 2011 in Buzzards Bay, Massachusetts. Lower and Upper SL 
describe the range for each interval and is measured in millimeters. 
For the age and gonad analyses in our study, we used 112 males and 
115 females. 
Proportion Proportion 
Lower SL 
Upper SL 
Males 
Females 
male 
female 
70 
80 
3 
0 
1.00 
0.00 
80 
90 
7 
1 
0.88 
0.13 
90 
100 
9 
6 
0.60 
0.40 
100 
110 
7 
8 
0.47 
0.53 
110 
120 
13 
5 
0.72 
0.28 
120 
130 
16 
2 
0.89 
0.11 
130 
140 
20 
1 
0.95 
0.05 
140 
150 
20 
2 
0.91 
0.09 
150 
160 
16 
3 
0.84 
0.16 
160 
170 
1 
11 
0.08 
0.92 
170 
180 
0 
19 
0.00 
1.00 
180 
190 
0 
19 
0.00 
1.00 
190 
200 
0 
16 
0.00 
1.00 
200 
210 
0 
18 
0.00 
1.00 
210 
220 
0 
4 
0.00 
1.00 
whelk. Males dominated the size range of 110-160 
mm SL and ages of 7-9 years, and females dominated 
the size intervals above 160 mm SL and ages of 10- 
14 years (Tables 1 and 2). For the 137 dissected male 
channeled whelk, the maximum SL recorded was 175.0 
mm and the maximum Wt was 490.6 g. Females typi- 
cally grew larger than males, reaching a maximum SL 
of 214.2 mm and a maximum Wt of 930.0 g (n=155). 
Penis length increased with SL in males (Table 3). 
The single exception was a 199.3-mm male that was 
removed from the study because histology showed that 
this whelk’s gonad was nonfunctional. Its gonad was 
empty of any gonadal precursors and contained only 
connective tissue. The sex of the whelk could not be 
determined on the basis of the gonad. It was recorded 
as a male only because a small penis (15 mm in length) 
was detected; a mature male at 165 mm SL normally 
would have a penis approximately 37 mm long. 
There was an exponential relationship between SL 
and Wt and a linear relationship between SL and LW. 
Covariance analysis of log 10 VW to logi 0 SL and sex (Ta- 
ble 4) showed that the male intercept and male slope 
were not significantly different from the female inter- 
cept and female slope. The results of this covariance 
analysis of log 1( )Wt indicate that log 10 VF^ regression 
equations for males and females are similar (Table 3). 
Because sex was not a significant factor, a combined 
regression equation that included both sexes was calcu- 
lated and indicated that logioWt was significantly re- 
lated to logio SL (Tables 3 and 4). Covariance analysis 
of LW versus SL and sex showed that slopes differed 
between sexes and that male and female 
intercepts were similar (Tables 3 and 4). 
The LW covariance analysis indicates 
that males and females have a similar 
initial size, but male LW may differ from 
female LW as SL increases. 
Growth rate 
The von Bertalanffy growth models 
for the sexes were significantly differ- 
ent (Table 5; Fig. 4, A and B). The old- 
est female was 14 years old, and males 
reached a maximum age of 12 years. 
Males and females had similar SL until 
about the age of 4 years, after which the 
curve for males started to plateau (Fig. 
4C). Females reached a larger maximum 
size and had higher annual growth rates 
than males (Fig. 4, C and D). The growth 
rates for males and females decreased as 
age increased (Fig. 4D). Covariance anal- 
ysis of sqrt (SL growth) versus sqrt (age) 
and sex indicated that the intercepts 
were not significantly different, and the 
male slope was significantly less than 
the female slope (Table 4). The sqrt (SL 
growth) covariance analysis indicates 
that males and females had a similar initial size, but 
male and female growth rates differed over time. 
Size at 50% maturity 
Females classified in stage I of gonad development did 
not exceed 130 mm SL (Fig. 5A) and 8 years of age 
(Fig. 5C). Females identified as ED did not exceed 160 
Table 2 
Number and proportion of each sex by age in years for 
channeled whelk (Busycotypus canaliculatus) collected 
in August 2010 and July 2011 in Buzzards Bay, Massa- 
chusetts. For the age and gonad analyses in our study, 
we used 112 males and 115 females. 
Age 
Male 
Female 
Proportion 
male 
Proportion 
female 
4 
1 
1 
0.50 
0.50 
5 
5 
5 
0.50 
0.50 
6 
12 
10 
0.55 
0.45 
7 
27 
5 
0.84 
0.16 
8 
26 
5 
0.84 
0.16 
9 
27 
8 
0.77 
0.23 
10 
9 
21 
0.30 
0.70 
11 
3 
34 
0.08 
0.92 
12 
2 
15 
0.12 
0.88 
13 
0 
5 
0.00 
1.00 
14 
0 
6 
0.00 
1.00 
