Body Shape Differences between Marine & Freshwater Species

Wart-covered frogfish and the slick tuna have distinct body shapes that help them survive their watery environments. A fish's body shape is a product of its environment. Marine fish must survive harsh ocean conditions; dodging predators and finding food require powerful body shapes. Freshwater fish often have combination body shapes to accommodate feeding in fresh water.

  1. Fusiform

    • A fusiform shape is seen on oval-shaped fish that are taller rather than wider; this shape is primarily seen in marine fish. The tuna's fusiform shape allows it to shoot torpedo-like through ocean waters. A salmon's torpedo shape gives it the strength to make its epic migration against river currents. Salmon lay eggs in freshwater but spend their adult life in saltwater.

    Depressed

    • A depressed fish shape is embodied by the stingray and some bottom feeders. Their flat body allows them to rest on the bottom and feed. In some cases a depressed fish can nestle into the sand to camouflage itself from predators. A depressed shape is found in the ocean with stingrays and flounders and angel shark species.

    Anugilliform

    • The anugilliform is a perfect circle when viewed head-on. The freshwater American eel exemplifies the anugilliform shape. Its long, narrow body allows the eel to hide in small crevices when predators are on the prowl or when hunting a meal. The American eel is a freshwater fish that spawns in saltwater but lives out its life in freshwater.

    Combination Shapes

    • Many fish bodies combine shapes to suit dynamic environments. The fish roaming near coral reef offer examples of these shapes. Puffer fish have spiky armor and the ability to exaggerate their size when threatened. A Seahorse clings to the underwater foliage as it feeds. Covered in armor with an s-shaped body, the seahorse is unlike any other fish in the sea. Freshwater fish combine multiple shapes depending on the lake, river or creek they inhabit. The head of a catfish is slightly depressed to accommodate bottom feeding while the body is rounder with multiple fins to power movement as the fish scours.