Wang Jinn-wang, the head of Taiwan's Coast Guard Administration (CGA), said after signing a fishery agreement with Japan on Wednesday that fishing boats that enter the waters off the Diaoyu Islands from outside Taiwan, including the Chinese mainland, will be expelled. His words triggered anger from the mainland.

Even from the legal perspective of the "Republic of China," such words have loopholes. The laws give a very ambiguous definition of the identities of mainland residents. Wang chose a sensitive time to abandon ambiguity and exclude fishermen from the mainland from the waters off the Diaoyu Islands, which is utterly inopportune.

The waters off the Diaoyu Islands have always been the traditional fishing area of Taiwan fishermen. Due to the restrictions, fishermen from the mainland seldom go there. There has never been a precedent of Taiwan's coast guard authorities expelling mainland fishermen. The CGA this time is more likely making much ado about nothing, seriously hurting the feelings of people on both the mainland and Taiwan.

Although there has been no open cooperation between the mainland and Taiwan on the Diaoyu Islands issue, tacit understandings do exist. The strong stance from the mainland side in safeguarding the sovereignty of the islands has undoubtedly strengthened Taiwan's status in its negotiations with Japan.

Taiwan alone cannot compete with Japan. As Taiwan seeks to maximize its interests, it won't side with the mainland. Taiwan authorities have been seeking a balance among the Taiwan public's demand for sovereignty over Diaoyu, its own politics, and the attitudes of the mainland, the US and Japan.

The latest statement from Taiwan's CGA is widely seen as a move to appease the pan-green camp and show appreciation for Japan's concessions in the fishery deal negotiations. But they obviously neglected the mainland's feelings.

The Taiwanese authorities clearly know that the more tacit understandings they share with the mainland, the more respect Japan will pay to Taiwan's interests. Totally splitting up with the mainland over the Diaoyu Islands issue would be a severe blow to Taiwan's capacity to bargain with Japan.

The mainland will not alter its Taiwan policy because of a false statement by Taiwan's CGA. However, this ludicrous statement should not be tolerated. The mainland public's strong discontent with the statement from the Taiwan CGA should not be neglected by authorities on both sides. Otherwise, the current positive momentum of cross-Straits relations will be undermined.