Competition is heating up among fishermen from South Korea, North Korea and China to catch blue crabs during the month of June in waters near the military-sensitive Northern Limit Line(NLL) de facto maritime border.

According to Seoul's Korea Coast Guard on Saturday, 300 Chinese fishing boats, 190 from North Korea and a hundred from South Korea were operating near the NLL so far this month.

Chinese fishermen are known to be operating across the NLL as they move up and down while the North Koreans mainly operate in waters north of the NLL and South Korean boats in designated waters south of the line.

June is considered the best month to catch blue crabs as they're the most plump ahead of the natural spawning season. Crabs caught this time of the year have a higher commodity value.

Near the NLL, which is akin to a maritime version of the Demilitarized Zone on ground, a rich fishing ground for blue crabs is naturally created as the area is banned from fishing and passage of vessels.

Amid rising demand and prices of blue crabs, Chinese fishermen are going out of their way to sweep them up.

In China, a kilogram of the crab cost 35-hundred South Korean won in 2014. This jumped to ten-thousand won last year and to 30-thousand in recent days.

North Korean fishermen are said to be exporting their entire catch in the Yellow Sea to China as a means of earning cash.