Notes: We like seeded multigrain bread for these appetizers; assemble them up to 1 hour ahead; drizzle avocado with lemon juice to retain color.
Toast bread. Spread pesto on one side of each slice. Pit, peel, and thinly slice avocado. Arrange avocado on bread slices, then cut each slice into quarters. Top with shredded lettuce or sprouts (optional), and smoked salmon or trout. Sprinkle with salt and pepper.