Japanese Wobbegong: Orectolobus japonicus

Family: Orectolobidae
Common name(s)

Japanese Wobbegong.

Identification

A small species of wobbegong with five groups of dermal lobes (skin flaps) on each side of head. Inner group attached to barbells, second group thin and small, third group long and weakly branched, fourth and fifth groups short and wide. Barbells long with fleshy bases.
Two equally sized dorsal fins. First dorsal origin over pelvic fin insertion. Caudal fin has a subterminal notch and a rounded terminal notch at midpoint of terminal margin.
No warty tubercles on head or body. Body light brown with many small pale spots, and 9 dark brown saddles with irregular, corrugated, pale edges formed by clusters of small pale dots.

Size

Maximum length 118cm. Size at birth approximately 21-23cm.

Habitat

Temperate seas. Found on rocky and coral reefs from the intertidal zone to 200m.

Distribution

The Japanese wobbegong is found around the coastlines of Japan, Korea, Mainland China, Taiwan, and Vietnam.

Conservation Status

LEAST CONCERN

The Japanese wobbegong inhabits rocky and coral reefs and as such, is taken mainly by hook and line. Where captured on commercial hook and line it is likely retained for human consumption. The Japanese Wobbegong is reported as taken by set nets, and possibly trawl, in Japan and retained (Compagno 2001, A. Yamaguchi pers. comm. 30/06/2020). In Taiwan, there is a small hook and line fishery in southern waters that may capture this species; elsewhere the hook and line fishery is mostly recreational charters. The charters have increased in effort over the past 10 years with government incentives to convert from commercial fishing (Fisheries Agency 2019, H. Ho unpubl. data 2019). In China, hook and line is mainly used in artisanal and subsistence fisheries which have a high fishing pressure as they account for ~25% of the Chinese domestic catch (Pauly and Le Manach 2015). However, the rocky and coral reef habitat of this species is not prevalent along most of the Chinese mainland which reduces the likelihood of capture in many areas in China. In Viet Nam, this species is also captured occasionally as bycatch by trawl and bottom longline at depths of 50–120 m (V. Quang unpubl. data 2020). Viet Nam fisheries effort has increased markedly over the past two decades and most marine stocks are now considered fully or over-exploited with a lack of adequate enforcement leading to essentially unregulated fisheries (Teh et al. 2014, FAO 2020).
The Japanese Wobbegong’s nocturnal habit provides refuge from daytime fishing pressure. Post release survival when discarded from hook and line fisheries is unknown, but it is high for other wobbegong species taken by gillnet (Ellis et al. 2017). Indirect and sublethal sources of mortality include habitat destruction and degradation. In both the East and South China Seas, there has been degradation of significant areas of coral reef habitat (Heileman and Tang 2009, Heileman 2009). In Viet Nam, dynamite and cyanide fishing, and sedimentation have caused widespread destruction of coral reefs (Jameson et al. 1995, FAO 2020).

Citations and References
Rigby, C.L., Bin Ali, A., Bineesh, K.K., Chen, X., Derrick, D., Dharmadi, Ebert, D.A., Fahmi, Fernando, D., Gautama, D.A., Haque, A.B., Ho, H., Hsu, H., Maung, A., Vo, V.Q., Sianipar, A., Tanay, D., Utzurrum, J.A.T., Yuneni, R.R. & Zhang, J. 2020. Orectolobus japonicusThe IUCN Red List of Threatened Species 2020: e.T161563A124507360. https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T161563A124507360.en. Downloaded on 02 January 2021.

Reproduction

Ovoviparous and lecithotrophic, i.e. the foetus is solely nourished by the yolk within the egg case.

Diet

Feeds on bony fishes, elasmobranchs (skates, sharks, and egg cases), cephalopods, and shrimp.
Wobbegongs are ambush predators that remain motionless while camouflaged against the reef. When an appropriately sized fish swims in front of its disguised mouth, the wobbegong lunges forward simultaneously stretching its mouth open. The process sucks water and fish into its mouth, which immediately snaps shut again, trapping its prey with needle-like teeth.

Behavior

Nocturnal. Rests by day on reef ledges or in crevices.

Reaction to divers

Easy to approach. Remains at rest, relying on camouflage unless harassed.

Diving logistics

The Japanese Wobbegong is quite difficult to find in most areas but it is seasonally common (during the cooler months) at Mikomoto Island on the southeast coast of the Izu Peninsula. Big Fish Expeditions runs a yearly Japanese shark diving expedition that focuses on this species and many other Japanese endemic elasmobranchs.

Similar species

Other Wobbegong Sharks There are no other members of the family Orectolobidae that enter Japanese waters. If the Japanese wobbegong’s range extends to the Philippines, there may be some crossover with the Indonesian wobbegong or perhaps even with un-described species endemic to the Philippines.