Adaptations in Fish

Adaptation

Purpose

Examples

Mouth

   
  • Terminal (at the end of the snout)

Feeds throughout the water

Walleye, sauger, northern pike

  • Under the snout/longer upper jaw

Feeds on prey it sees below it; usually feeds off the lake or river bottom

Bullhead, whitefish, carp,sucker

  • Angled upward/longer lower jaw

Feeds on prey it sees above it; small fish, or aquatic insects, often at surface of water

Goldeye, rock bass, smallmouth bass, tullibee

  • Ventral (under the head)

Feeds off the bottom

Sturgeon

  • Sucker-shaped

"Vacuums" up food off the bottom; eats aquatic insects, vegetation

Sucker, sturgeon

  • Strong jaws and well-developed teeth

Feeds on other fish

Northern pike, walleye

  • With barbels

Feeds off the bottom; Can sense food in murky water

Catfish, bullhead, stonecat, sturgeon

Eyes

   
  • Large

Feeds by sight

Walleye, perch, goldeye, bass

  • Small

Likely feeds off the bottom and relies on barbels to detect food

Catfish, bullhead, stonecat, sturgeon

Spines

For protection or to stiffen fins for swimming

Catfish, bullhead, stonecat, perch, walleye, bass, sturgeon

Body Shape

   
  • Rounder, flat bellied

Feeds off or rests on the bottom; less conspicuous to predators

Sucker, catfish, sturgeon

  • Oval, fairly long

Prefers more open water or a few weeds

Walleye

  • Oval, very long, eel-like

Fast-moving in quick bursts; Agile around rocks and weeds

Northern pike, burbot

  • Thin, shorter, disc-shaped

Agile around rocks/weeds; round shape harder for predators to swallow

Bass, perch

  • Torpedo-shaped

Stream-lined for high speed or swimming in currents

Brook trout, rainbow trout, arctic char

Scales

  • Large

Used for protection; speed not needed to catch food

Carp, sucker

  • Small or non-existent

Fish more streamlined and fast-moving to catch prey

Northern pike, catfish, burbot

Colouration

  • Fairly uniform, no markings

Swims in open water

Walleye, goldeye

  • Stripes

Hides in weeds for protection or to ambush prey

Perch, smallmouth bass, rock bass

  • Mottled

Hides in rocks or on bottom

Northern pike, young sturgeon

  • Dark on top

Less visible to predators above it

Catfish, sturgeon, carp

  • Light coloured belly

Less visible to predators below it

Perch, walleye, sturgeon, sucker, catfish