Indeed, one of the best dishes in the summer is fish taken fresh from the lakes. It’s usually a speciality of the lakeside restaurants, at least here on the Swiss French side.
Aldi, Lidl and Denner can be your friends as they’re often very much cheaper than Migros, Coop, Manor, etc. I do most of my weekly food shopping at Aldi with only a few purchases from Denner and Migros and very occasionally from Lidl. Lidl can be good though if you insist on “brand” names as they have good offers which come up much more frequently than they do in Migros or Coop.
Another possibility to consider later in the year is Aligro. They’re like the Uncle Sam’s, CostCo warehouse type markets and they are supposed to be opening a store in/near Zurich some time this year. You can get a Gourmand card which gives you a discount if you spend over CHF100. Again, it’s good for bulk buying if you’ve got a large freezer/storage space although I don’t find them particularly cheap when compared to Aldi/Lidl, but they’re a bit cheaper than Migros/Coop etc. Their website is: www.aligro.ch so might be worth having a look at.
AND they stock American Spare Ribs if you’re into BBQ.
Shopping over the border is really worth it imho: on average we buy stuff for two people for about 100chf/week (before even getting the taxes back). This means a shopping cart literally full of whatever we want: food (meat, dairy, vegetables, fruit, pasta, sweets, ice-cream etc), cosmetics, hygiene products, cleaning products, beer...