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How Crappies Feed.

Fish Biology--Fish feed using various strategies, which are often classified as ambush or cruise feeding behaviors. In ambush feeding, predators wait motionless for long periods for prey to swim by, before repositioning. Cruise feeding is constant swimming in search of prey. Pike often, but not always, feed using an ambush strategy, while fish like tuna, or perhaps walleyes following a school of shiners in open water, are cruisers.

Scientists studying feeding behaviors in fish have identified a third, intermediate type of foraging strategy called saltatory. In this type of feeding, fish behave in a stop-and-go manner, scanning for brief periods while motionless, and if prey isn't detected, they swim a distance and stop again to scan, and repeat.

Scientists have discovered that young white crappies are saltatory feeders, stopping to scan for Zooplankton and repositioning and moving again before stopping again to scan* These young planktivorous crappies stop to scan for an average of 0.3 to 1 second, depending on prey size.** Young bluegills feeding on Zooplankton also have been identified as saltatory feeders, pausing for an average of 0.1 to 0.4 seconds to scan. Grayling is another saltatory feeder.

The search space for predators generally has a maximum pursuit angle (horizontal), height (vertical), and distance. Researchers found that for saltatory feeding crappies, prey location ability is greatest in the "forward-facing hemisphere." Most pursuits occur in the 0- to 30-degree wedge of the visual field (0 degrees being a line straight forward from the eyes). Pursuit distances also are longer in this area, and are progressively shorter farther out to the sides of the field toward 180 degrees.

Saltatory foraging also is seen in ground-foraging birds, the researchers explain, as well as in birds foraging on flying insects, as they fly from perch to perch. Lizards also are saltatory feeders. Saltatory feeding behavior is often studied in the laboratory with larval and juvenile planktivorous sizes of fish, but some of these species don't remain planktivores as adults. Crappies, for example, often switch to eating small fish as adults, but wether they retain a saltatory strategy is unknown. But old habits can be hard to break. Just in case, it might be a good idea to give crappies a second or two to scan for your presentation, detect it, and begin pursuit, before you pull it away. Don't give up the pursuit before they have a chance to pursue.

Dr. Rob Neumann

* Browman, H., and three co-authors. 1990. Correlation between histological and behavioral measures of visual acuity in a zooplanktivorous fish, the white crappie (Pomoxis annularis). Brain Behav. Evol. 35:85-97.

** O'Brien, J. W., B. I. Evans, and H. I. Browman. 1989. Flexible search tactics and efficient foraging in saltatory searching animals. Oecologia 80:100-110.

by DR. ROB NEUMANN, STEVE QUINN, DR. HAL SCHRAMM & RALPH MANNS

Caption: Most pursuits occur in the 0-to 30-degree wedge of the visual field on either side of 0 degrees.

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Title Annotation:Bits & Pieces: Blending Fishery Science with Everyday Fishing
Author:Neumann, Rob
Publication:In-Fisherman
Date:Oct 1, 2018
Words:487
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