Mackerel were in large numbers as far north as Nootka Sound in 1997 where they were entertaining to catch with trout gear off the resort's floating dock. But they were hell on outbound smolts to include virtually all released from Barkley Sound hatcheries: http://www.spokesman.com/stories/1997/jun/23/mackerel-wreaking-havoc-with-salmon/.

The article also references an El Nino of 1992/1993 with a similar mackerel invasion.

As far as this year I have to believe if there was to have been such an invasion it would have already occurred and in any case outbound smolt have already dispersed.
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Remember to immediately record your catch or you may become the catch!

It's the person who has done nothing who is sure nothing can be done. (Ewing)