Rising Sea Temperatures Off the Southern Coast of Japan Linked to Increased Shark Incidents
Despite experts indicating that tiger sharks in the waters surrounding Kyushu Island generally do not pose a significant threat to humans, they warn of a surge in the population of “aggressive” tiger sharks in the area this summer.
The Japanese Ministry of the Environment issued a heatwave warning for 21 out of 47 prefectures on July 5, highlighting the impact of the El Niño phenomenon on ocean temperatures.
Rising sea temperatures are pushing sharks into shallow waters of Japan, creating issues for fish farms. (Photo: Shutterstock).
A television report from All Nippon News on July 3 showcased the consequences of changing ocean temperatures and currents, depicting sharks breaking through nets surrounding an aquaculture farm in Kinko Bay.
At least two sharks, each approximately 3 meters long, consumed groupers that were awaiting transport. Ultimately, the two sharks died after getting entangled in the nets, but around 1,700 groupers were either eaten or swept out to sea through gaps in the nets.
The fish farm owner, Yosuke Fukami, estimated the incident caused his company about 10 million yen in losses. “We have seen sharks offshore, but never thought they would come so close or eat fish in the nets. Fortunately, no one was injured,” he stated.
Experts believe these sharks could be bronze whaler sharks or sand sharks, typically found in tropical and subtropical regions, including around Okinawa and southern Kyushu.
According to the International Shark Attack File, among the 16 recorded attacks by bronze whaler sharks, only one resulted in a fatality, while sand sharks are attributed to five global attacks with no fatalities.
Dr. Taku Horie, a marine biology professor at Tokai University, noted: “These sharks are not commonly found in these waters and are very rare in Kinko Bay.”
“Sand sharks typically approach shallow, sandy areas like coastal zones and bays, and they may have gotten caught in the nets while hunting what appeared to be a tasty morsel inside the fish farm’s nets. Rising sea temperatures could be a factor, but tidal currents and abundant offshore food sources could also play a role“, he explained.
Dr. Horie mentioned that sand sharks are primarily nocturnal and rarely attack humans, and it would be “excessive to restrict people from swimming in the sea during the day” as the summer vacation approaches. However, if a shark is spotted, he advises to keep a safe distance and exit the water immediately.
He added that there are still many more dangerous predatory species lurking offshore. “The number of aggressive tiger sharks seems to be increasing in the waters around Kagoshima, but larger specimens remain offshore and are rarely seen in coastal areas. Nonetheless, surfers should still exercise caution in the early morning and evening,” he cautioned.
