Being an east sider, what is/when is a slack tide.
Slack tide is generally that period in the tide cycle when the tide reaches it's full stage -either full high or full low- prior to shifting back the other direction. For a short period (depending on location) the tide goes "slack" and doesn't really flow in or out for a bit before it reverses direction.
In the case above, I would like to know if that pile of perch were caught at high slack or low slack; there's often a big difference between the two for fishing purposes.
edit:
Being an east sider, what is/when is a slack tide.
The pause between tides. He didn’t say wether it was high or low slack. 
That's the concise version.
