An Estuary or Common Seahorse (Hippocampus kuda) uses a solitary Fan Green Seaweed (Avrainvillea erecta) leaf as its anchor. Seahorses use their elongated snouts to feed on small drifting by prey. They are slow to digest their food due to their extremely simple digestive systems. The absence of a stomach means that they must eat continuously to stay alive.
These toothless and stomachless fish can devour up to 3000 little crustaceans, such as brine shrimp, in a single day. In addition to shrimp, which is their favourite food, they also feed on zooplankton and and fish larvae.
Their long trumpet-like snout acts a bit like the aspiration pipe of a vacuum cleaner, with their mouths resembling a one-way trapdoor. When a little shrimp comes close enough, the seahorse opens its mouth fast enough to create a vacuum and sucks in its prey so quickly that there is almost no escape possible for the crustacean. The very small mouth of this intriguing animal means that the sucking force is very small, and for the seahorse to catch its prey, it must be very close to the seahorse's mouth. Because seahorses lack teeth, the little shrimp is swallowed whole and quickly passes through an inefficient digestive system that tries to absorb as much nutrition as possible in a relatively short period.
Filming this scene was quite easy. The subject was small and almost immobile, with little chance of fleeing the scene. However, seahorses have a very annoying habit when they are confronted by a photographer or underwater videographer; they tend to turn their heads away in a way that makes them nearly impossible to film.
The seahorse in this underwater video clip has a rather large leaf of solitary Fan Green Seaweed behind it, making a smooth turning impractical unless the seahorse were to push the leaf away, which would be rather unlikely.
A trick to prevent a seahorse from turning its head away from your lens or underwater dome would be to have your dive buddy take a position on the opposite side. By doing so, you actively obstruct the seahorse from turning away from the filmmaker or underwater photographer. Make sure to set your aperture wide enough to create a shallow depth of field so that everything more than 30cm/1ft behind your subject is blurred, including your buddy.
When filming a subject close to or on the bottom, it's best to position your camera in a stable, immovable manner and film horizontally (avoid filming from above). Set up your lights so that you do not overexpose any parts of the scene. Start filming and keep the camera rolling. After a minute or two, you will likely have more than enough decent footage to broadcast.
In post-production, you need to add the sounds of the seahorse gulping down the poor little shrimps. Although this process is probably silent, it's nice to find a matching sound in a sound database. Use your imagination, but keep it credible; the sound of, for example, a noisy vacuum cleaner would be really out of place.
This short underwater videoclip has been filmed in Bali, Indonesia 🇮🇩
Bring the beauty of the ocean to life with our online Marine Wildlife Videography course!