Natanson et al.: Gestation period and pupping seasonality of Squalus acanthias off southern New England 
477 
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Figure 1 
Map of locations where spiny dogfish (Squalus acanthias) were sampled off 
southern New England, between Massachusetts and Rhode Island, and off New 
Jersey from July 2013 to July 2015. A gear-restricted area was established as 
an accountability measure for windowpane (Scophthalmus aquosus) in 2014 
and 2015. 
aca, of extra pups in the bottoms of the bags containing 
the samples, and of partly flaccid uteri, with or without 
1 or more embryos. For these reasons the number of 
free-living embryos per female is a biased (and prob¬ 
ably low) estimate of fecundity, whereas the number of 
developing oocytes of the largest group of developing 
oocytes in the ovaries may be an upper estimate, some 
may ultimately not have been fertilized. The number of 
embryos per female was calculated both with total em¬ 
bryos (free-living and candled litters: mean=4.5 embry¬ 
os, range=l-ll embryos, 77=542) and with free-living 
embryos only (mean=4.3 embryos, range=l-9 embryos; 
n=338) for comparison with results of other publica¬ 
tions (Table 2). Because of the similarity in these es¬ 
timates, total embryos were used in relation to female 
size classes. The number of maturing oocytes for the 
next litter was difficult to discern in newly mated fe¬ 
males; therefore the fecundity estimates based on num¬ 
ber of developing oocytes were taken only from females 
with visible embryos (mean=5.3 embryos, range=l-10 
embryos; 77=443). 
The mean values from all 3 types of fecundity es¬ 
timates (developing oocytes, total embryos, and free- 
living (only) embryos) indicate a significant (P<0.0001) 
positive relationship between litter size and maternal 
size (Fig. 2, A-C). This increase in litter size with ma¬ 
ternal size is also evident when the total and free-liv¬ 
ing embryo data are broken down into 5-cm STL size 
Table 2 
Mean number of free-living and total embryos per female spiny dogfish (Squalus 
acanthias) and sample size for each size class of females, defined by 5-cm inter¬ 
vals of stretched total length in centimeters. Values for total embryos (candled 
and free-living embryos combined) are given in parentheses. 
Size class (cm) 
Mean 
Standard deviation 
Sample size 
75-79 
2.25 (3.25) 
1.50(1.58) 
4(8) 
80-84 
3.26 (3.45) 
1.29(1.31) 
57 (95) 
85-89 
4.08 (4.23) 
1.32 (1.31) 
136(203) 
90-94 
4.89 (5.11) 
1.33 (1.31) 
114(184) 
95-99 
4.70(5.20) 
2.20 (2.19) 
20 (40) 
100-104 
6.00 (6.33) 
2.38(2.84) 
7(12) 
All size classes 
4.27 (4.50) 
1.55 (1.59) 
338 (542) 
