Here is a great Apple/Android Seafood Watch App for a quick reference guide on seafood choices and seasons.

For the pico de gallo:
4 Beefsteak tomatoes, diced
1 large red onion, diced
2 jalapeños, seeded and diced
1 bunch cilantro, roughly chopped
4 garlic cloves, diced
1 tbsp Kosher salt
1 tsp cumin

For the black bean puree: 
1-15 oz can black beans, drained
½ cup freshly squeezed lemon juice
½ cup extra virgin olive oil
1 tsp freshly ground black pepper

For the tacos:
8-6 inch corn tortillas
16 oz yellow tail flounder fillet, cut into strips
Kosher salt
Freshly ground black pepper
2 tbsp canola oil
4 cups shredded little gem or romaine lettuce
1 avocado, sliced
1 cup crème fraîche
2 red radishes, shaved
4 lime wedges

Directions for the pico de gallo: In a food processor, pulse together tomatoes, onion, jalapeños, cilantro, garlic, 1 tbsp Kosher salt and cumin until incorporated; set aside.

Directions for the black bean puree: In a food processor, process together beans, lemon juice, olive oil and pepper until smooth; set aside.