To restock a lake means to put more fish in it because there are very few left. The lake was restocked with roach last year. to bring in more supplies to replace those that have been used
If you restock something such as a shelf, fridge, or shop, you fill it with food or other goods to replace what you have used or sold. I have to restock the freezer Back on Flatbush Avenue, Pong is busy restocking his shelves with cucumbers and coconuts