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Fish schools are one of the best examples of aggregation in animals. Schools are groups of fish that act as a single unit, and are characterized by a streamlined structure and uniform behavior for the purposes of avoiding predators and finding food. Individuals join schools for selfish reasons; therefore, in order for schooling to improve fitness, the schools must offer benefits greater than the costs of increased visibility to predators, increased competition, and energetic instability. These costs are balanced by the benefits of schooling behavior in the presence of predators, altering patterns according to food availability, and engaging in behaviors such as sexual or mixed schooling. Individuals also alter their behavior by competing for the safest spots within the school, jostling to be the first to eat, and leaving the school if does not benefit them as an individual. Study of schools also focuses upon the physical and sensory mechanisms that allow the school to act and respond as a unit, despite being comprised of, sometimes, hundreds or thousands of individuals. This too is evolutionarily relevant as the density, volume, and structure represent the results of selective pressure while maintaining the conflict between those on the outside of the school or unrelated individuals and the rest of the school. As a whole, schools provide insight into aggregate behavior as they can be manipulated, observed and modeled to provide answers.

Author: Aparna Bhaduri

Trinidadian Guppies
The Trinidadian guppy is one of the most studied schooling fish. Its prevalence and ease in breeding both accommodate its study.

Introduction

Humans have been interested in schooling behavior in fish for centuries, often for very practical reasons. Before scientists marveled at schools as perfect examples of aggregation and products of fine tuned evolutionary action, schooling was important to fisherman. Understanding how and when these schools would arise, how they would travel, and where they could be found were important in many coastal cities and civilizations. Aristotle himself once commented that the fish school ought to be what a society strives to be: as such, the human interest in schooling fish is one of the oldest forms of animal behavior study, one that has taken on an increasingly scientific perspective.

As evolutionary theory predicts, each individual within the school competes for resources, survival, and reproductive potential (Hamilton 1970). A school is a group of fish ranging from just a few fish to thousands of fish that acts like a single entity, where the behaviors that it engages in such as swimming, avoiding predation , and foraging benefits each member of the group distinctly (Edelstein-Keshet 1999). Therefore, questions about schooling behavior center on the evolutionary reasons for schools, potential costs and how they are overcome, as well as specific examinations of the school dynamic .

The methods of studying fish are quite diverse: observation , experimentation , comparison , and computer modeling are some of the most common ways fish schools are studied. The schooling fish that are studied range from the easily manipulated Trinidadian guppy, to the common herring, to parrotfish that are found near corals ( [link] ). Hundreds of species of fish school, and many of them have been studied.

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Source:  OpenStax, Mockingbird tales: readings in animal behavior. OpenStax CNX. Jan 12, 2011 Download for free at http://cnx.org/content/col11211/1.5
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