FISH ATLASGLOBAL FISH ENCYCLOPEDIA

FISH SPECIES

Long-bodied Fish

Explore fish with elongated, anguilliform or ribbon-like silhouettes, and learn how length changes locomotion and foraging.

FISH ATLAS / FIELD GUIDELong Bodied FishIN THIS CHAPTER01 / Characteristics02 / Lifestyle03 / Species04 / Field notes
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01 / NATURAL HISTORY

Characteristics

Elongated body plans reduce hydrodynamic drag, allow passage through tight apertures, and feature reduced or absent pelvic fins combined with extensive multi-vertebral muscular flexing systems.

  • 01Anguilliform wave propulsion
  • 02Crevice & conduit navigation
  • 03Reduced appendages & low drag
管臀魚（Aulopyge huegelii）
Long Bodied Fish

02 / LIFESTYLE

Lifestyle

True eels swim via full-body anguilliform waves, sending lateral bends down their entire length to push against water, allowing them to reverse direction inside narrow subterranean burrows. Needlefish and pikes maintain a rigid elongated torso, keeping the body straight until their posterior fins and muscular caudal peduncle unleash sudden, explosive forward lunges.

OBSERVATION INDEX

  1. Full-body anguilliform undulation
  2. Reverse movement inside burrows
  3. Rigid body ambush alignment

03 / SPECIES

Representative species

View all species

Discover representative species illustrating the ecological diversity, morphologies and adaptations of this group.

04 / FIELD NOTES

A closer look

Why do eels and morays lack pelvic fins?

Pelvic fins create hydrodynamic drag and easily catch on obstructions when navigating tight crevices, burrows and rock cracks. Over evolutionary time, appendages were reduced or lost in favor of continuous median fins.

How do elongated fish like gar and needlefish hunt?

Rather than undulate their whole bodies, they hold their long torsos completely straight to resemble floating sticks or debris, then unleash rapid lateral head snaps or tail bursts to impale unsuspecting prey on their toothed jaws.