28 
Fishery Bulletin 11 7(1 -2) 
Table 3 
Proportional measurements of males (in % of total length) from 6 regional populations of Okamejei kenojei and their morpho¬ 
logical differentiation significance among populations. Ranges are followed by mean (±standard deviation in parentheses). 
Numbers under “significance” indicate P values in ANCOVA. Populations separated by < are significantly different. NS=not 
significant. Population abbreviations are given in Table 1. 
EC 
n=13 
YS 
n=3 
SJ 
n= 36 
EK 
n =3 
OS 
n=10 
NP 
n =30 
Significance 
Total length (mm) 
97-408 
428-455 
104-453 
185-390 
323-435 
98-566 
(258 ±99) 
(441 ±11) 
(334 ±97) 
(271 ±87) 
(409 ±31) 
(376 ±154) 
Disc length 
54.0-58.4 
54.2-59.0 
54.0-61.4 
56.6-61.7 
55.1-61.1 
54.5-60.2 
NS 
(56.7 ±1.2) 
(56.2 ±2.1) 
(57.3 ±1.7) 
(59.1 ±2.1) 
(57.6 ±1.8) 
(58.5 ±1.6) 
Disc width 
63.5-69.9 
64.4-70.7 
64.2-73.4 
65.6-73.5 
61.5-72.7 
66.9-74.3 
NS 
(67.9 ±2.1) 
(67.1 ±2.7) 
(68.1 ±2.7) 
(69.6 ±3.2) 
(67.0 ±3.0) 
(70.6 ±2.0) 
Tail length 
48.5-54.4 
46.9-50.2 
46.2-51.4 
45.6-50.8 
45.6-49.1 
45.7-54.1 
NS 
(50.1 ±1.5) 
(49.0 ±1.5) 
(48.5 ±1.2) 
(47.4 ±2.4) 
(47.3 ±0.8) 
(48.1 ±2.5) 
Dorsal head length 
19.4-23.3 
19.0-20.5 
18.9-24.5 
21.6-24.5 
20.4-23.4 
18.0-22.6 
NS 
(21.5 ±1.3) 
(19.8 ± 0.6) 
(21.1 ±1.5) 
(22.7 ±1.3) 
(21.3 ±0.8) 
(20.6 ±1.0) 
Dorsal snout length 
12.9-16.8 
13.0-13.7x 
12.5-17.9 
14.3-18.1 
13.8-16.4 
11.9-16.1 
NS 
(15.1 ±1.3) 
(15.1 ±1.3) 
(14.4 ±1.3) 
(15.8 ±1.7) 
(14.5 ±0.7) 
(14.2 ±0.9) 
Eye diameter 
3.0-5.0 
2.6-3.4 
3.1-4.3 
3.4-3.6 
2.8-3.5 
2.6-4.4 
NS 
(3.7 ±0.6) 
(2.9 ±0.4) 
(3.6 ±0.3) 
(3.6 ±0.1) 
(3.2 ±0.2) 
(3.3 ±0.4) 
Distance between orbits 
4.1-5.2 
4.7-5.0 
4.3-5.2 
3.7-5.1 
4.8-5.6 
4.9-5.8 
< 0.001 [EC, YS, SJ<NP] [SJ<OS] 
(4.6 ±0.4) 
(4.9 ±0.1) 
(4.8 ±0.2) 
(4.6 ±0.6) 
(5.1 ±0.3) 
(5.3 ±0.2) 
Ventral head length 
26.4-30.5 
27.2-29.2 
27.2-31.5 
29.0-32.8 
28.5-31.0 
26.0-30.7 
NS 
(29.3 ±1.1) 
(28.1 ±0.8) 
(29.5 ±1.1) 
(29.5 ±1.1) 
(29.6 ±0.7) 
(29.0 ±1.1) 
Ventral snout length 
14.0-17.8 
13.0-14.2 
12.5-19.1 
14.4-18.5 
14.2-16.7 
11.9-16.5 
NS 
(15.7 ±1.4) 
(13.5 ±0.5) 
(14.9 ±1.5) 
(16.4 ±1.7) 
(14.7 ±0.7) 
(14.4 ±1.2) 
Prenasal snout length 
10.2-14.2 
10.0-10.9 
9.6-15.6 
11.5-15.0 
11.1-13.3 
9.4-13.5 
NS 
(12.3 ± 1.4) 
(10.6 ±0.4) 
(11.8 ±1.5) 
(13.4 ±1.4) 
(11.6 ±0.6) 
(11.6 ±1.0) 
Distance between nostrils 
7.0-8.4 
7.2-8.2 
6.9-8.8 
7.6-8.4 
7.2-8.3 
7.6-9.4 
NS 
(7.8 ±0.4) 
(7.6 ±0.4) 
(7.9 ±0.4) 
(8.0 ±0.3) 
(7.8 ±0.3) 
(8.6 ±0.4) 
Distance between 
14.1-16.1 
13.9-14.8 
13.4-17.0 
14.1-15.7 
13.1-15.1 
14.8-17.5 
NS 
1st gill openings 
(15.0 ±0.6) 
(14.2 ±0.4) 
(15.1 ±1.0) 
(15.1 ±0.7) 
(14.2 ±0.7) 
(16.2 ±0.7) 
Morphological comparisons 
Measurements and count Excluding TL, measurements 
of 12 characters (1 in males and 11 in females) differed 
significantly among some of the regional populations 
(Tables 3 and 4); for example, distance between orbits 
in males, NP individuals was characterized by a more 
widely separated orbits than those of other popula¬ 
tions (Table 3; Fig. 3C). NP females were easily distin¬ 
guished from females of other populations in having a 
broader disc, smaller eye, shorter head and snout, and 
more widely separated nostrils and gill openings (Table 
4; Fig. 3, B, F, H). Furthermore, OS females were also 
characterized by a smaller eye, and by a longer head 
and snout than the corresponding features of females 
of other populations (Table 4; Fig. 3, B and F). Among 
4 regional populations (EC, YS, SJ, and EK), EC fe¬ 
males had longer tails than females of SJ, SJ females 
had a shorter head and snout than females of EK, and 
YS females had a smaller eye than females of EC and 
SJ (Table 4; Fig. 3, B and F). 
Individuals (>ca. 300 mm TL) from NP usually had 
more than 4 nuchal thorns (range: 3-12) in both sexes, 
but similar-size individuals from the other 4 popula¬ 
tions (except OS) usually had 2 or 3 (range: 2-4) (Fig. 
4, A and B). Individuals of both sexes from OS (>ca. 
300 mm TL) usually had 2 nuchal thorns (range: 1-3), 
which were somewhat lower numbers overall than 
those of other populations. Among smaller specimens of 
males and females (< ca. 200 mm TL), NP individuals 
had 2 nuchal thorns, those of other populations having 
only 1. 
Maturity size Clasper length of males fitted a single 
sigmoid curve against TL (Fig. 5). Specimens with 
clasper length >24% TL were considered mature be¬ 
cause they possessed both alar and malar thorns and 
hard claspers. The size of mature NP males ranged 
from 454 to 566 mm TL (average: 493 ±32 mm TL), but 
between 343 and 455 mm TL (average: 410 ±25 mm 
TL) in other populations. The estimated maturity size 
in males differed significantly between NP and other 
three populations, excluding EK and YS (P<0.05). 
Number of rows of tail thorns in females also fitted 
a single sigmoid curve against TL (Fig. 6, A and B) 
and were similar to clasper growth. Individuals from 
