Natanson et at: Gestation period and pupping seasonality of Squalus acanthtas off southern New England 
475 
the tip of the snout to the upper lobe of the caudal fin 
pulled downward to align with the body) to the nearest 
millimeter on each specimen. A girth measurement was 
taken behind the pectoral fins of each specimen. Each 
fish was weighed to the nearest tenth of a kilogram. 
After external measurements were taken, an inci¬ 
sion was made from the cloaca through the pectoral 
girdle along the ventral surface to retract the belly flap 
and expose the abdominal cavity. Organ terms follow 
those of Hamlett and Koob (1999). Both sides of the 
female spiny dogfish reproductive tract are functional; 
therefore, both sides of each specimen were dissected 
and measured. Measurements were taken to the near¬ 
est millimeter and weights to the nearest tenth of a 
gram in the following order: ovary weight, diameter of 
each of the largest group of oocytes and at least 1 of the 
next size group. In pregnant females, all embryos were 
measured (FL and STL, in centimeters along a straight 
line), weighed (in grams) (without external yolk which 
was weighed separately [in grams]) and visually ex¬ 
amined for developmental stage of the litter (i.e., ac¬ 
cording to the condition of the umbilical scar). If there 
was no external yolk, the embryo was weighed and the 
internal yolk was removed and weighed (in grams). Lit¬ 
ter sizes and sex of an embryo were also recorded. In 
many cases it was clear that pups had been aborted 
before dissection and these instances were noted. De¬ 
velopmental stages were the following: mature ovarian 
oocyte, candled embryo (embryo and yolk covered by a 
membranous envelope (stage 1 in Hisaw and Albert, 
1947), free-living embryo (no longer candled), embryo 
with external yolk, and embryo with no eternal yolk 
and with healing umbilical scars. 
Fecundity 
Three estimates of fecundity were calculated: 1) by 
counting the number of oocytes in the largest group 
of oocytes in the ovaries, which were presumed to be 
the next litter; 2) by using total embryo count (candled 
and free-living embryos), and 3) by using counts of only 
free-living embryos. Mean number of all 3 indices per 
female were plotted against maternal size. Addition¬ 
ally, the data were presented by 5-cm maternal size 
increments for comparison with data from previous 
studies. Fecundity measures for each 5-cm maternal 
size class and female spawning stock biomass, esti¬ 
mated by using a 3-point moving average (Rago and 
Sosebee 3 ), were plotted over time to determine poten¬ 
tial signs of density dependence. Fecundity data from 
1998 through 2002 were obtained from Sosebee (2005) 
and data from 2006 to 2009 were obtained from Bub- 
ley (2010). Data summaries that included only aver¬ 
ages across years were plotted at the midpoint of the 
time series. Additionally, correlation analyses were 
conducted to determine correlations between the mean 
fecundity of each 5-cm maternal size class and spawn¬ 
ing stock biomass (SSB), estimated by using a 3-point 
moving average (Rago and Sosebee 3 ), and with relative 
abundance estimates based on mean number of mature 
females caught per tow during the NOAA Northeast 
Fisheries Science Center spring bottom-trawl survey 
(Silva, 1993). 
Reproductive seasonality 
Gestation period was determined by plotting the size 
of the embryos over time, assuming samples were from 
the same stock. The concurrent increase in follicle size 
with embryo size (see the Results section) also allows 
one to infer the mating period on the basis of the in¬ 
crease of follicle size in the ovaries followed by a sud¬ 
den decrease and presence of fertilized eggs in the 
uterus. Each shark was also examined for evidence of 
mating scars. 
Size of full-term embryos 
The determination of the size that the embryos were 
considered full term was based on observation of um¬ 
bilical scars, size of internal yolks, and maximum sizes 
of embryos in relation to minimum sizes of free-living 
swimming individuals. These data were confounded by 
the differences in size of term embryos in relation to 
maternal size (see the Results section). 
Results 
Between July 2013 and June 2015, 622 mature fe¬ 
male dogfish ranging in size from 75.3 to 104.2 cm 
STL (mean 88.5 cm STL; 66.8-94.5 cm FL [mean 79.2 
cm FL]) were sampled. Between July 2013 and June 
2014, spiny dogfish were obtained from SNE between 
Massachusetts and Rhode Island in all months, except 
October, when a federal government furlough preclud¬ 
ed sampling (Table 1, Fig. 1). Between July 2014 and 
June 2015, samples were obtained in in this region in 
6 out of 12 months (Table 1). In October and Decem¬ 
ber 2014 samples were obtained from off shore of New 
Jersey in an attempt to maintain the monthly sam¬ 
pling time series. No samples were available during 
September 2014 and March and May 2015 as a result 
of the establishment of a gear-restricted area as an ac¬ 
countability measure for windowpane (Scophthalmus 
aquosus) in 2014 and 2015 (GARF0 67 ). This measure 
restricted fishing in the areas where spiny dogfish are 
6 GARFO (Greater Atlantic Regional Fisheries Office). 2014. 
Greater Atlantic Region Bulletin. Northeast multispecies 
common pool fishery fishing year 2014 regulations, 7 p. 
Greater Atlantic Regional Fisheries Office, NOAA, Glouces¬ 
ter, MA. [Available from website.] 
7 GARFO (Greater Atlantic Regional Fisheries Office). 2015. 
Greater Atlantic Region Bulletin. Groundfish fishermen: 
NOAA Fisheries approves Framework 52 to the Groundfish 
Plan—southern windowpane flounder restricted gear area 
reduced in size, 3 p. Greater Atlantic Regional Fisheries 
Office, Greater Atlantic Regional Fisheries Office, NOAA, 
Gloucester, MA. [Available from website.] 
