Why do many gasterosteiform fishes hold a vertical position in their habitats?

Many gasterosteiform fishes adopt a vertical position in their habitats primarily for defense. This posture serves two main purposes:1

• Camouflage: By orienting themselves vertically among corals, plants, or other animals, these fishes effectively blend into their surroundings.1
• Predator Deterrence: This vertical orientation helps present the fish's body spines or shields to predators that are typically adapted to hunt prey oriented in a horizontal plane.1

While most members of the order utilize this vertical stance for protection, there are exceptions. For instance, snipefishes swim both forward and backward in a vertical plane but do not rely on marine growths for shelter. Additionally, seahorses use their prehensile tails to grip corals or plants, and they can further enhance their camouflage by changing color or utilizing long skin filaments to hide in grassy areas.1