Experts said Chinese trawlers catch a large amount of squids that head south from North Korean waters, resulting in a decline in South Korea's catch.

A yearly migratory species, squids are known to spawn in waters off South Korea's southernmost island of Jeju and the southeastern port city of Busan, head north in spring and return to their spawning grounds between July and September.

The number of Chinese fishing ships operating in North Korean waters surged to up to 1,900 in 2014 from 140 a decade ago. South Korea's Ministry of Oceans and Fisheries puts the number at 700 ships as of October this year.

Most are vessels over 200 tons and are allowed to operate in North Korean waters if they pay fees for fishing, sparking fears over the depletion of North Korean fish stocks.

Chinese fishing vessels are also said to damage fishing nets and other gear set by South Korean fishermen while sailing through open seas south of Jeju toward North Korea waters.

The ministry said it has been steadily calling on Beijing to ensure that Chinese fishing boats make a detour so as not to inflict damage on the South Korean fishing equipment.

There are high tensions between Seoul and Beijing after a Chinese boat illegally fishing in South Korean waters sank a 4.5-ton Coast Guard speed boat in a collision 10 days ago. The speed boat was on a mission to capture a Chinese fishing ship poaching there when another Chinese boat rear-ended it. The incident has worsened a bilateral conflict over the long-drawn issue of Chinese boats operating illegally in South Korean waters. (Yonhap)