(replying to myself) Some googling says that it was layoffs in general, in all sectors there (not just canning), including Chicken Of The Sea closing a plant there entirely. There were a lot of articles written on the subject at the time, all of them quite critical of the wage increase, citing it as the primary factor. So yes, even if automation wasn't involved, it looks like the wage increase was a factor in that particular microcosm.

Still not convinced that it means we shouldn't raise the minimum wage on the mainland.