Pieter Claesz

I've recently become intrigued with food in an historical context. Therefore, I'd like to explore why there is so much food in art. Is the food on display something the artist actually ate, or does it represent something else? What did the food actually taste like? How was a meal composed? By whom? The picture above is by dutch artist Pieter Claesz (1597-1660), around 1642. The meal consists of bread, a herring and a glass of wine. The wineglass is very prominently displayed, the fish is on a pewter plate, and there's also a stoneware jug in the background. Is this a display of wealth, or is it just a meal?
(I also wonder if that really is a herring. Looks like a european perch (Perca fluviatilis) to me...