Most fish species, like these Longfin Spadefish (Platax teira) face the current while swimming underwater primarily for different reasons: maintaining stability and maximising efficiency in locomotion.
Swimming against the current allows fish to maintain stability in the water. When fish face the current, the water flows directly over their gills, ensuring a constant supply of oxygenated water. This positioning enables them to extract oxygen efficiently, which is crucial for their survival. If fish were to swim with the current, they would experience a reduced flow of water over their gills, potentially leading to oxygen deprivation and suffocation.
Additionally, facing the current provides fish with better control over their position and movement in the water. By swimming against the current, they can counteract the pushing force of the water and maintain their position or move more precisely. This is particularly important for fish that inhabit environments with strong currents.
Another reason why fish face the current is to maximise their efficiency in swimming. Swimming against the current reduces the resistance the fish experiences, allowing them to move more easily through the water. Fish have streamlined bodies and are adapted to minimise drag as they swim. By facing the current, they take advantage of the reduced resistance, enabling them to conserve energy and swim more efficiently.
Facing the current also helps fish with their foraging and feeding activities. Many fish species rely on their ability to swim against the current to maintain their position while searching for food. By facing upstream, they can remain stationary or slow their movement, making it easier to detect and capture prey items that are carried by the current towards them.
It's worth noting that while most fish face the current, some species have adapted to different swimming orientations depending on their ecological niche and environmental conditions. For example, bottom-dwelling fish may face downstream to take advantage of the flow of food particles or to avoid being swept away by the current. Ultimately, the swimming behaviour of fish is influenced by a combination of ecological factors, including water currents, habitat structure, and specific adaptations of each species.
This school of Longfin Spadefish was filmed in a deeper section of a Maldivian Thila (a completely submerged pinnacle covered in corals and often exposed to strong currents). During this particular dive, no underwater video lights were used. To compensate for the limited amount of light, I adjusted the aperture to a larger than normal size (small f-stop) and increased the ISO (higher sensitivity of the camera's sensor). Consequently, this resulted in more noise (a decrease in quality, often seen as small specks in the image) and darker footage. However, in post-production, it is relatively easy to reduce most of the noise in the footage by utilising noise-reducing software. The images were color corrected using the exposure and saturation settings of the editing software. Additionally, the yellow colour of the Longfin Spadefish's pectoral fins was enhanced using a colour mask. It is generally easier to correct underwater footage that is underexposed compared to overexposed images. Overexposed material is often challenging to colour correct since most of the colours have been washed out. Overexposed footage can be identified by bright white patches in the video.
This short underwater videoclip has been filmed in the Maldives 🇲🇻
For another in-depth description about Longfin Spadefish please go to our vlog post 23 or click on this link: https://www.beyondscuba.com/post/spadefish-in-the-blue
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