Fish Tacos With Watermelon Salsa

4 cups diced seedless watermelon

1/2 small red onion, finely diced

1/2 cup roughly chopped fresh cilantro

Juice of 2 limes, plus lime wedges for serving

1 jalapeno pepper, seeded and finely diced

1 tablespoon plus 2 teaspoons extra-virgin olive oil, plus more for brushing

Kosher salt

1 pound skinless wild striped bass fillets

1 teaspoon chipotle chile powder

1 romaine lettuce heart, thinly sliced

8 corn tortillas

1 avocado, sliced