Viducic et al.: Reproductive characteristics for Prionace glauca in the North Atlantic Ocean 29 
for the best fitting model (Burnham and Anderson, 2002). 
Models with A; values <2 are indicative of no evidence of 
a statistical difference between models. Those with A, val- 
ues >10 are indicative of poor fit relative to the best fitting 
model and are generally unsupported. 
On the basis of the selected model, the median size at 
maturity (i.e., Ls) or Ws, the inflection point of the rela- 
tionship where P=0.5) was calculated from the fitted model 
parameters as —},)/B,. Confidence intervals around L;, and 
W;, were bootstrapped from the selected model to 1000 
repeated samplings of the maturity data (Harry et al., 2013) 
by using the boot package (vers. 1.3-20; Canty and Ripley, 
2017) in R. For all models, normalized diagnostic plots of 
the residuals were examined visually to evaluate the appro- 
priateness of model assumptions (Zuur et al., 2010). 
Revisiting Pratt (1979) 
Pratt (1979) did not present a value for median size at 
maturity for females. Using Pratt’s data (TP1) and staging 
the subadult phase as immature, we calculated median 
size at maturity for females. Additionally, for comparison 
to his analysis, we calculated the male median sizes at 
maturity using the TP1 data. 
Median age at maturity 
To improve existing age-structured relationships, age at 
median maturity was estimated by inserting the calculated 
Ls for each sex into the sex-specific von Bertalanffy growth 
functions calculated by Skomal and Natanson (2003). 
Results 
Specimen collection 
A total of 857 blue sharks were dissected for repro- 
ductive analysis (488 males and 369 females) between 
1971 and 2016. Samples were obtained in all months, 
with most of the samples obtained between June and 
September (79.3%, n=680) and the remainder between 
October and May (20.6%, n=177) (Table 1). Recreational 
fishermen caught the majority of sharks (66.6%, n=571), 
followed by commercial fishermen (23.3%, n=201), and 
scientists on research vessels (8.8%, n=75). The source of 
1.3% (n=11) of samples could not be determined because 
the source was not noted at the time of dissection (Suppl. 
Table 1) (online only). Sharks from the entire study ranged 
in size between 62.0 and 300.0 cm FL and between 1.0 
and 213.4 kg, although size ranges of samples and num- 
ber of samples were different in each time period and 
analysis (Table 1). 
Maturity 
Females Data collected from 1971 through 2016 were 
used to examine female reproductive condition (see the 
Table 1 
Number and size range (in centimeters and kilograms) of blue sharks (Prionace glauca) by sex, time period (TP), 
and month of capture per TP in the western North Atlantic Ocean along the northeastern coast of North America 
between New Jersey and the Flemish Cap. Sampling occurred in 2 TPs: 1971-1977 (TP1) and 2003-2016 (TP2). 
Values are also provided for the interim period of 1978-2002. n=number of samples. 
Males Females 
1978-2002 
TP1 1978-2002 TP2 TP1 
155 109 224 183 76 110 
Fork length (cm) 102.0—279.0 62.0—285.0 64.7—300.0 108.0—263.0 114.0-273.0 63.0—257.0 
Weight (kg) 17.7-122.5 1.0-174.0 1.4-213.4 9.1-112.5 8.2-146.0 1.7—110.0 
January 
February 
March 
April 
May 
June 
July 
August 
September 
October 
November 
December 
0 
BP RWNAINUHAANNNO 
SCRPROONOONWN He 
