Subject:
A Pygmy Hawkfish (Cirrhitichthys oxycephalus) is nervously hopping around. These little predators of very small fish and crustaceans have no swim bladder. Fish control their buoyancy with this specialised organ. This flexible-walled, gas-filled sac, located in the dorsal portion of the body cavity, allows the fish to stay at its current water depth without having to expend energy in swimming, just like a scuba diver uses their BCD (Buoyancy Control Device) or jacket.
Many species of fish lack a swim bladder and are adapted to a life on the bottom of the sea. Other fish, like some cartilaginous species (rays and sharks), lack a swim bladder but use fat and oil reserves to control their buoyancy. Additionally, many rays and some shark species lose their buoyancy when they stop swimming. These species use dynamic lift as a way to control their buoyancy: by swimming at a certain speed, they generate enough lift to remain buoyant in the water column.
Besides controlling the fish's buoyancy, the swim bladder is important for hearing in some species. The swim bladder interconnects with the fish's inner ear through a series of little bones called the Weberian ossicles. These bones conduct the vibrations of sound to the swim bladder, where the pressure of sound increases the fish's hearing, somewhat like an amplifier.
Amongst those species that lack a swim bladder and are adapted to a benthic life are the hawkfishes (Cirrhitidae), a family of rather small, territorial bottom-dwelling fishes. Their lower pectoral fins are thick and often used to wedge themselves in place on the substrate, rocks, or coral branches.
Hawkfish are sequential hermaphrodites, and males often have a harem of a few females. They are ambush predators of small reef fish and little crustaceans. When hungry, they lie in wait until an unsuspecting victim ventures in their vicinity before suddenly darting for it.
Technique:
The colours in this clip are, though natural, quite bright and striking and may be too vibrant for some. Nevertheless, colours are extremely important in video and film because they create the video’s mood and atmosphere, and can convey emotions and messages to the viewer. Underwater videography presents a unique challenge when it comes to capturing colours, as water filters out different wavelengths of light and alters the way colours appear. This is why underwater videographers often use special equipment like orange filters and underwater video lights and techniques to enhance and correct colours in their footage.
One of the most common techniques used in underwater videography is colour correction. This happens during the editing process and involves adjusting the colour balance and saturation levels of the footage to compensate for the loss of colour caused by water. By adjusting the levels of red, green and blue colours, a underwater videographer can bring back the natural colour tones of the underwater environment and make the footage look more vibrant and realistic.
Another technique used in underwater videography is the use of artificial lighting. By using powerful underwater lights, the underwater videographer can bring out the natural colours of the underwater environment and illuminate the subject of the footage. Artificial lighting can also be used creatively to highlight specific areas of interest in the footage or to create a certain mood or atmosphere.
Ultimately, the colours in underwater videography play a critical role in creating a compelling and immersive video experience. Whether the colours are bright and vibrant or muted and subdued, they help to communicate the beauty, complexity and diversity of the underwater world to the viewer.
Reducing the colour’s vibrancy would make this clip less playful.
For another in-depth description about hawkfish please go to our vlog post 34 or click on this link: https://www.beyondscuba.com/post/juvenile-lyretail-hawkfishes
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