FWIW, a couple of comments on Lima restaurants. First, if you're into fish, you should aim to dine at lunch, not dinner. Traditionally, seafood in Lima is eaten when still fresh, which means off the boat at dawn and consumed before the sun goes down. Which is not to say you can't get seafood in the evening, but most of the good "cevicherías" are only open for lunch, which means from noon until around 5pm (it's a relaxed affair). There are a lot of excellent lunch-only seafood restaurants in Lima, with new ones opening all the time. You can try El Mercado, La Mar and Pescados Capitales to start, all three are located in Miraflores on or near Av. La Mar.

Second comment, IMHO Astrid y Gastón is past its prime. Gastón Acurio no longer owns or directly manages the place, and I think frankly they have gotten a little stale, and they're kind of stuck in the 90s, so to speak. Two places that I would recommend more for dinner in Lima are Los Cavenecia, in Barranco (a district well worth a visit anyway) and Capital, in Miraflores. There are many others too, Lima being a gastronomic paradise.