Misawa et al.: Population structure of Okame/ei kenojei 
33 
Figure 7 
Typical coloration of 4 regional populations of Okamejei kenojei. (A) FAKU 140518, 384 mm 
total length (TL), adult female, East China Sea (B) BSKU 116603, 289 mm TL, immature 
male, Sea of Japan, (C) FAKU 140521, 430 mm TL, adult male, Osaka Bay, (D) BSKU 112173, 
462 mm TL, adult male, Pacific coast of northern Japan. 
route of the Kuroshio Current has been stable at least 
since the last glacial period (Kojima et ah, 2000), shap¬ 
ing the distributional range of various coastal species 
along the Japanese Archipelago (Matsuura, 2012). 
The genetic and morphological divergence of ocel- 
late spot skate populations between the Sea of Japan 
and East China Sea, suggested by significant F ST val¬ 
ues (Table 2) and measurements (Table 4), is mirrored 
in several coastal marine species. For example, Liu et 
al. (2007) disclosed 3 mtDNA lineages in redlip mul¬ 
let {Chelon haematocheilus )—lineages that diverged 
among the Sea of Japan and the East and South China 
seas during Pleistocene glaciations. In addition, genet¬ 
ic and morphological divergence was also detected be¬ 
tween EC and YS, which are separated by the Tsushi¬ 
ma Strait and Tsushima Current (Fig. 1). Similarly, ge¬ 
netic divergence between the Yellow Sea and Japanese 
coast of the East China Sea has been noted in several 
marine fishes, including the white croaker ( Pennahia 
argentata), spotted halibut ( Verasper variegatus), and 
gizzard shad ( Konosirus punctatus) (see Han et ah, 
2008; Sekino et al., 2011; Gwak et al., 2015). As noted 
in the above examples with C, haematocheilus and K. 
punctatus, 3 regional populations (EC, YS, and SJ) of 
O. kenojei also diverged on account of Tsushima Strait 
and the Tsushima Current, which act as geographical 
barriers. 
Implications for fisheries management Small and ben¬ 
thic (or benthopelagic) elasmobranch species tend to 
exhibit more distinct population structures at smaller 
spatial scales than those exhibited by large pelagic 
species (Larson et al., 2017). In fact, movement pat¬ 
terns of some skate species investigated in tagging 
studies, have shown that most had a small home range 
(within a 100-km 2 area) (Walker et al., 1997; Hunter 
et al., 2005; King and McFarlane, 2010; Neat et al., 
2015; Farrugia et al., 2016; Vargas-Caro et al., 2017) in 
spite of their potential ability to migrate hundreds of 
kilometers (King and McFarlane, 2010). Regarding O. 
kenojei, a lack of tagging studies has meant no insights 
on migratory range, although the extensive population 
structure found in this study suggests that the species 
has a small home range. 
Because fish populations have a unique set of dy¬ 
namics, such as recruitment, growth, and mortality 
that influence current and future status, it is impor¬ 
tant, even within the same species (Pope et al., 2010), 
to define management units (MUs) based on population 
structure and to execute subsequent assessment and 
management of stocks according to each MU. Clearly, 
MUs for O. kenojei need to be set according to the pop¬ 
ulation structure of the species because of the genetic 
and morphological differentiation of populations among 
the investigated regions. We suggest at least 6 MUs for 
