"which" refers to "the catch of all wild fish".
Without "of all wild fish", "the catch" is almost meaningless here. The catch of what? Not clear. In another word, "of all wild fish" defines "catch". In turn, "which" modifies the noun "the catch of all wild fish".
-- by 会员 silent7706 (2010/5/26 13:16:04)
恩,有道理,谢谢啦!那是不是这种情况下都是指代中心词呢?