Nature’s Perfect Design

Fish are among the most efficient movers in the animal kingdom, perfectly adapted for life in water. Their ability to swim relies on a combination of body shape, muscles and specialized fins working in harmony.

Most fish move forward by flexing their bodies from side to side in a wave-like motion. Powerful muscles along the body contract alternately, pushing against the water. The tail fin, or caudal fin, acts like a paddle, generating thrust with each sweep. The faster and stronger the tail beats, the quicker the fish moves.

Fins provide stability and steering. The dorsal (back) and anal (belly) fins prevent rolling, while the pectoral and pelvic fins help with balance, braking and making sharp turns. Some species, such as tuna, have stiff, streamlined bodies built for speed, while others, like eels, rely on more flexible bodies for slithering through narrow spaces.

A fish’s streamlined shape reduces drag, allowing it to glide through water with minimal effort. Scales and a coating of mucus further decrease resistance, making swimming more energy efficient. Gills, located behind the head, allow fish to breathe as water flows past them during swimming.

From the darting movements of minnows to the powerful bursts of salmon navigating upstream, swimming is not only a survival skill but also a key part of feeding, migration and reproduction. In short, fish are master swimmers, shaped by millions of years of evolution to move with precision and grace in their watery world.

Halibut – A Fish Of A Different Speed

When it comes to swimming technique, halibut are a fascinating case because, unlike many fish with symmetrical bodies, they are flatfish that live most of their adult lives on the ocean floor.

Halibut begin life as typical, upright-shaped fish. As they mature, one eye migrates to the other side of the head and they adapt to life lying flat. Despite this unusual body plan, they are strong and capable swimmers.

• Body movement: Instead of using side-to-side body undulations like streamlined fish, such as salmon, halibut rely primarily on their broad, powerful tail (caudal fin). By sweeping the tail back and forth, they generate strong bursts of thrust.
• Fin use: Their large dorsal and anal fins, which run almost the full length of their bodies, also help propel and stabilize them. These fins undulate in wave-like motions, giving halibut an extra push when needed.
• Swimming style: Halibut are not built for long-distance cruising. Instead, they are ambush predators. They lie camouflaged on the seafloor, then swim in short, explosive bursts to capture prey such as herring, cod or squid.

While halibut may look awkward compared to streamlined fish, their flattened bodies are perfectly adapted to a bottom-dwelling lifestyle. They can settle flush against the seafloor to avoid detection, then use powerful, sudden movements to chase down a meal or avoid predators.