Fisherman would like it to be true that scientific dating methods are just too unreliable. The usual target for claims of inaccuracy is carbon-dating, though scientists actually use various methods, and carbon-dating is only used for samples within a certain timeframe.
However, the Watch Tower Society says carbon-dating is reliable as far back as about 3,500 years ago (Awake!, 22 November 1981, p. 15). Well within that period is the earthquake that occurred during Amos' time. And, naturally, the facts of that event also show JW chronology to be wrong. See Amos' earthquake.