Bait Ball: Unusual Fish Behavior Avoids Predator Fish Feeding at Night

Trick or Treat?

October 31, 2013

Written by Andrew Bruckner, PhD

Several hours after dark on Halloween, a large school of bait fish attracted to the lights given off by the Golden Shadow, congregated near the aft deck to feed on plankton. This fish behavior (and the lights) also attracted other predators, including remoras, jacks, sea snakes and squid.

Remoras, predator fish feeding at night.

The predators made repeated rushes at the fish, forcing the bait fish to the surface. As a defensive behavior, they formed a tightly packed spherical bait ball. In this last ditch effort to avoid being eaten, the bait fish swam rapidly in circles, moving from the surface of the water to several meters below, and disbanding and reforming the bait ball in rapid succession.

Bait fish forming three different bait balls. This lasted for over an hour; quite unusual fish behavior.

The bait ball lasted for over an hour, which is quite unusual. This gave several brave scientists the opportunity to enter the water for a closer look at the bait fish behavior.

João Montiero photographing the bait fish.

http://www.youtube.com/watch?v=9lWNpviVF6Y&width=550&height=309

Fish feeding at night.

Photos: 1-5 by Nick Cautin

Video by João Montiero

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