360 
Fishery Bulletin 118(4) 
The objective of this study was to estimate median length 
at maturity (L;,) of the Pacific angel shark in the eastern 
GOC. Differences in life history characteristics have import- 
ant management implications if they result in different 
population responses to fishing pressure. 
Materials and methods 
The artisanal elasmobranch fisheries of Sonora and Sinaloa, 
Mexico (Fig. 1), operate open-hulled fiberglass boats 
that are 5.5-7.6 m long and have outboard motors with 
55-115 hp. Pacific angel sharks were collected at fishery 
landings during 1998-2005 (for details, see Bizzarro et al., 
2009). Length, sex, and maturity stage of specimens were 
recorded. Total length (TL) was measured in centimeters 
from the tip of the rostrum to the end of the stretched cau- 
dal fin. Length-frequency distributions were constructed to 
examine the structure of the sample. Normality of length 
distributions was verified by using the Kolmogorov— 
Smirnov (K-S) test. If normality data were rejected, the 
nonparametric Mann—Whitney test was used to compare 
mean lengths of each sex. A chi-square test was used to 
compare the observed sex ratio of the entire sample and the 
United States 
Mexico | 
5 
Sonora 
< SS 
~ Sa 
NS Vata 
} % ‘California 
Sinaloa. > 
ie S \ 
PacificOcean [| As 
0 80160 320km 
(Lon nnd} 
116°W 114°W 112°W 110°W 108°W 
Figure 1 
A map of the study area, showing the fishing grounds 
(black areas) in the Gulf of California off Sonora and 
Sinaloa, Mexico, where Pacific angel sharks (Squatina 
californica) were captured between 1998 and 2005. 
ratio of maturity stages (immature to mature) against the 
expected value of 1:1. Reproductive status was assessed 
through macroscopic examination following Clark and von 
Schmidt (1965) and Castro (2000). Mature males had hard- 
ened claspers that could rotate from the base by directing 
the claspers anteriorly on the inner side of the shark. The 
inner clasper length was measured from the point of inser- 
tion of the clasper to the clasper tip. The clasper length 
was plotted against TL to show how the clasper grew as an 
individual approached maturity. Females were considered 
mature when they had ripe oocytes (>20 mm in diameter) 
and a thickened uterus or when they were pregnant. His- 
tograms and box plots of lengths by maturity stage were 
constructed to identify outliers. 
For statistical treatment, the classification of maturity 
stages used 0 for immature individuals and 1 for mature 
individuals. Binary logistic regression between TL and 
maturity data was applied to estimate the regression 
coefficients a and b. The significance of the difference in 
maturity stage between sexes was tested with an analysis 
of covariance by applying a general linear model with a 
significance level of 0.01. With the coefficients a and b, the 
proportion of mature sharks by length was determined by 
using the following logistic function (maturity ogive): 
1 
Pm», = 5 
a Gy Fl 
© 
1+ exe 
where Pm = the proportion of mature fish given the length 
(TL); 
Ls = the median length of the sample when half 
of the individuals had reached maturity 
(L;9=a/b); and 
® = the steepness of the model (®=L,,)/a). 
All the parameters and their 95% confidence intervals 
(CIs) were estimated with Minitab!, vers. 19.0 (Minitab, 
State College, PA). 
Results 
A total of 306 Pacific angel sharks (192 females and 114 
males) were measured (y7=19.9, P<0.05). The mean length 
for females was 72.91 cm TL (standard deviation [SD] 
16.88) with a range of 23-100 cm TL; the mean length for 
males was 80.32 cm TL (SD 13.32) with a range of 
25-99 cm TL (Fig. 2A). For both sexes, the length distribu- 
tions had maximum frequencies in the length class of 
85-90 cm TL, a class that mostly corresponds with mature 
individuals (Fig. 2, B and C). Results of analysis of the 
normality of length distributions with the K-S test indi- 
cate non-normal distributions of length for males (K—-S 
test: D=0.209, P<0.01) and females (K-S test: D=0.174, 
P<0.01). The nonparametric test revealed significant 
' Mention of trade names or commercial companies is for identi- 
fication purposes only and does not imply endorsement by the 
National Marine Fisheries Service, NOAA. 
