34 
Number of fish 
~g——- 9-- ---§- 
Fishery Bulletin 120(1) 
60 80 100 180 200 
Fork length (cm) 
Number of fish 
0. 0 
3 0 0 0 
100 120 140 160 180 200 220 2 
Fork length (cm) 
60 80 
Number of fish 
mo. 
160 180 200 
Fork length (cm) 
Figure 3 
Stacked histograms of length and maturity stage, by time period, for male blue sharks (Prionace 
glauca) caught in the western North Atlantic Ocean: (A) time period 1 (1971-1977), (B) interim 
period (1978-2002), and (C) time period 2 (2003-2016). Dark gray bars represent values for juve- 
nile fish, and light gray bars indicate values for mature fish. The number of juvenile or mature 
fish is provided within each bar. 
varied slightly, within 10 mm FL for all time periods, and 
the L;, for males increased from Pratt’s (1979) estimate 
(183.0 cm FL original, or 184.1 cm FL recalculated) regard- 
less of what comparison was used (Table 4). However, it is 
important to determine if this change is real or an artifact 
of sampling method or sample distribution. 
In previous studies on the shortfin mako (U/surus oxy- 
rinchus) (Natanson et al., 2020) and the common thresher 
shark (Alopias vulpinus) (Natanson and Gervelis, 2014), 
comparisons of data over a 40-year period have shown that 
changes in principal dissectors over time did not affect 
the data, indicating that, probably because of intensive 
training and standard protocols, personnel changes were 
not a factor leading to the maturity shift. However, we had 
to consider the possibility that changes in maturity analy- 
ses or personnel conducting the study may have influenced 
these results. For example, Pratt (1979) based maturity 
status on the presence of spermatophores. The current 
standard for male maturity is clasper calcification (Castro, 
2011). Spermatophores have actually been shown to be 
present before clasper calcification in a variety of species 
(Castro, 2011), and such presence of spermatophores may 
have biased the data toward a lower median size at matu- 
rity. We restaged data from Pratt (1979) on the basis of 
