Schooling Behavior
1
SCHOOLING BEHAVIOR
[Part of the material and experimental design in this exercise have been adapted from Keenleyside (1975,101-104) and
some material has been adapted from Brooks & Yasukawa (n.d.)]
Objectives:
1.
2.
3.
4.
Application of the scientific method to testing specific hypotheses in animal behavior.
Begin to think about variables and how they are controlled in an experiment.
Begin to design proper controls in an experimental situation.
Learning to write the hypothesis, results, discussion, and literature cited sections of a
lab report.
5. Continued development of critical writing skills.
6. Continue learning how to properly present and interpret data.
Things To Do Before Coming to Lab:
1. Read this laboratory exercise.
2. Read the “GUIDELINES FOR WRITING LAB REPORTS”
3. Read Lewis, Gaffin, Hoefnagels, & Parker (2004, pp. 828-835).
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INTRODUCTION
Organisms can be found living in a myriad of situations, from solitary living to living in large groups
of very well organized conspecifics (members of the same species). For example, many species of
snakes lead a mostly solitary life and only come together to reproduce or when hibernating. Other
organisms, such as honeybees, live in large, well-organized groups with a high degree of division of
labor among its members. In honeybees, for example, there are hive cleaners, workers, and foragers,
and even reproduction is relegated to a few individuals in the hive. [What name do you think is given
to a group composed of members of different species?]
You probably already know many terms used to describe various degrees and types of groupings of
organisms; such as solitary, aggregations, packs, herds, flocks, schools, prides, and gaggle. On one end
of the spectrum of social groupings are the “aggregations,” which can be thought of as groupings of
conspecifics that lack any well-organized societal structure. However, it is generally assumed that
aggregations would not exist unless the organisms involved were deriving some sort of benefit from that
grouping, even if it is not a well-developed society. Often such benefits are not obvious and may be
something as simple as “safety in numbers.” On the other end of the spectrum of social groupings are
groupings such as the honey bee society, in which there is a very well defined division of labor and a
highly organized “societal structure.” In fact, the term “eusocial,” which refers to the highest form of
societal development in insects, is used to describe honeybee organization. This lab exercise studies one
such grouping, namely SCHOOLING behavior in fish.
Schooling Behavior in Fish
What is schooling behavior and what are the characteristics of a school?
Keenleyside (1975, 101) defines a fish school as “…a group in which the animals stay together
because they are showing positive social responses to each other, not because they are responding
similarly to a common external factor.” Below is a partial list, compiled from Maier (1998, 327-328)
and Keenleyside (1975, 101), of characteristics of fish schools.
1. A school is made up of conspecifics of very similar size.
2. Members of a school exhibit precise spacing among themselves.
3. There is no particular leader of a school.
4. Members of a school are “…mutually attracted to each other.” (Maier, 1998, 327). This
“mutual attraction” is probably what Keenleyside (1975, 101) calls “positive social responses.”
5. Two of the senses that fish use to maintain a school are visual cues and their lateral line systems,
which sense movements in the water. (What other sensory cues do you think fish might use to
form and then maintain a school?)
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What benefits might a fish derive from being a member of a school?
Maier (1998, 327-328) and Brooks & Yasukawa (n.d., 1) both talk about the benefits that may
accrue to individual members of a school. They agree (see the next two paragraphs) that two of the
major benefits of schooling are (1) escaping from predators and (2) foraging success.
Schooling behavior helps individuals to escape predation. The basic premise is that there is “safety
in numbers.” In other words, the likelihood that a particular fish will be caught by a predator goes down
when it is a member of a school and goes up when it swims as an individual. Why? Also, in a school
there are many individuals watching for a predator and, in some cases, perhaps the size of a school
dissuades a predator from attacking.
Schooling behavior also seems to increase foraging success. Since a school consists of many
individual fish, the likelihood that prey will be found increases as compared to food finding success by a
solitary fish.
Schooling Behavior and the 4 Categories of Behavioral Questions
During last week’s lab exercise, you learned the four categories of questions that animal behaviorists
commonly ask about particular behaviors being investigated (Dewsbury 1978, 5-7). Those four
categories have been listed below with a couple of sample questions pertaining to fish schooling in each
category. (Can you add questions to each category?)
1. Immediate Causation
-- What senses (e.g. sight, hearing, touch, etc.) do fish use to maintain a school?
-- Do schools only consist of conspecific fish of the same size?
2. Development
-- Do juveniles school as effectively as adults?
-- Is schooling an “instinctive” behavior or is it learned over time?
3. Evolution
-- What selection pressure(s) might have led to the evolution of schooling behavior?
-- Why isn’t schooling behavior exhibited by all species of fish?
4. Function
-- Does schooling behavior affect an individual’s success at escaping predators?
-- Is foraging behavior improved by schooling?
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LAB ACTIVITIES
I. Ethogram
Sometime, either during the lab period or on your own time, watch the schools of fish in the large
stock tanks and see what you can come up with for a few behaviors that could be used to construct an
ethogram. Also think about how you would describe and name those behaviors. (No formal assignment
is due, but this would be good practice in reinforcing what you learned on pp. 5-7 in last week’s lab
exercise.)
II. Experiments
A. General Information
YOU WILL BE WRITING SECTIONS OF A FORMAL LABORATORY REPORT
BASED ON THESE EXPERIMENTS. THEREFORE, BE SURE TO RUN THE
EXPERIMENTS AND COLLECT THE DATA CAREFULLY.
1. There are many questions one could ask about schooling behavior in fish, from which
hypotheses may be formulated, such as;
Does a particular species of fish exhibit schooling behavior?
What senses are fish using to form a school?
Is a school made up of a particular sex and/or age group?
Are schooling fish better able to escape predation than non-schooling fish?
Are the members of a school more successful at finding prey than is a solitary fish?
And many other such questions
2. However, the hypotheses you will be testing in lab today have to do with school size and
species composition of schools. Specifically you will test the following two hypotheses.
a. Hypothesis I: An individual fish of a schooling species of fish will select to be a
member of (near) a large school of conspecifics, rather than be a
member of (near) a small school of conspecifics.
b. Hypothesis II: An individual fish of a schooling species of fish will select to be
a member of (near) a conspecific school, rather than be a member of
(near) a school of heterospecifics.
3. The two species of fish available in the lab are Zebra fish and Tetras, both of which exhibit
schooling behavior. The two stock tanks are labeled as to which species each contains, but the
two species are also visually distinctive. AS THE EXPERIMENTS PROGRESS, BE SURE
NOT TO MIX THE FISH IN THE TWO STOCK TANKS TOGETHER!
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B. General Procedures:
1. Selecting the Experimental Species. This has been done for you.
a. To test Hypothesis I, one half of the class will use Zebra fish and the other half of the
class will use Tetras. (Your instructor will tell you which groups are to use which fish.)
b. To test Hypothesis II, both species of fish will be used by all groups in the class.
2. The Experimental Apparatus
a. At each table are the following pieces of equipment:
-- one 10 gallon aquarium with the two long sides divided into two equal regions by
having vertical black lines drawn on the glass on the outside of the aquarium. (See
Fig.1 on p.6.)
-- two, one gallon glass jars
-- one meter stick
These will only be needed if the lines on the sides of the
-- one glass marker
aquarium become faded during the experiments.
-- one or two fish nets
-- one stop watch
-- one glass, “release cylinder”
-- one 3” square piece of plexiglas
Fig. 1: Side view of a 10 gal. aquarium, partitioned into two equal regions
X
Y
10A
1A
2A
A = a particular species of fish (either Zebras or Tetras)
b. Other pieces of equipment available in the lab for use in these experiments:
-- Two large stock tanks, one containing zebra fish and the other containing tetras.
-- A smaller tank beside each larger stock tank. The smaller tank is to keep the test
fish of each species that have been used in prior experiments.
CAUTION: Due to the nature of the experiments in the lab exercise, the lab floor may become
wet in places, which may make walking slippery. (When wet, cement floors become very
slippery.) Therefore, BE VERY CAREFUL AS YOU WALK AROUND THE LAB.
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C. Experiment A:
Hypothesis I = An individual fish of a schooling species of fish will select
to be a member of (near) a large school of conspecifics,
rather than be a member of (near) a small school of
conspecifics.
1. A good experimental test of Hypothesis I would be to place 10 fish of species A in a one
gallon jar and place that jar in the center of “region X” in the aquarium; then place 2 fish of
species A in the second gallon jar and place that jar in the center of “region Y” of the
aquarium. Then release a “test” fish of species A into the center of the aquarium and record
how much time the test fish spends in each of the two regions of the aquarium for a 6 minute
period. If the test fish does prefer a school of larger size, then it should spend most of its time
in “region X” of the aquarium. What follows are the procedures you should follow in order
to set up this test and, regardless of which species you will be using, it will be referred to
as “species A” during the following outline of specific procedures in “#4” below.
2. As a group, be thinking about the variables in this experiment and about a proper control
group. Also be thinking about what senses and/or cues the test fish might be using to
determine where it will spend its time. (What senses could the test fish be using? What
senses could the test fish NOT be using?)
3. Determine who in your group is going to do what in setting up and running the experiment.
For example:
a. Who is going to do the timing of how long the test fish spends in each of the 2 regions of
the aquarium?
b. How is this going to be timed?
c. How will it be determined that the test fish has changed from one section of the aquarium
to another, and who will determine that?
d. If a test fish does change from one section of the aquarium to another, that means the
timer must stop recording the time for the section the fish left and start recording the time
for the new section. HOW?
e. What else is your group going to have to work out ahead of time?????
4. The Procedures For Testing Hypothesis I.
a. Fill the two one gallon jars and the one “release cylinder” with water from the aquarium
at your table. (Never fill these jars from the stock tanks because that will add too much
volume to the aquarium at your table.) Fill each gallon jar to a height just below the
bottom thread on the jar’s neck and fill the “release cylinder” to a level of about one inch
from its open top.
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b. Take the two filled gallon jars and the “release cylinder” to where the stock tank for
“species A” is located. Using a fish net, put 10 fish of species “A” in one of the gallon
jars, 2 fish of “species A” in the other gallon jar, and one fish of “species A” in the
“release cylinder.”
CAUTION --- These gallon jars and “release cylinder” can become quite
slippery and difficult to carry. Therefore, when carrying one, be sure you have
a firm grip (with a hand underneath it) before attempting to carry it to or from
the stock tank.
c. Return to your table with the gallon jars and the “release cylinder.”
d. Place the gallon jar with 10 fish of “species A” in the center of “section X” of your
aquarium and place the second gallon jar with 2 fish of “species A” in the center of
“section Y” of your aquarium.
CAUTION: The jars are slippery so be careful. Also, DO NOT bang the jars
against the sides of the aquarium and do not drop the jar on the bottom of the
aquarium. Doing so could easily break the glass sides or bottom. Lower each
jar into the aquarium slowly and with great caution and with one hand under
each jar.
e. Place the square of plexiglas over the open end of the “release cylinder.” Hold one hand
around the cylinder and hold the plexiglas tightly over the opening of the “release
cylinder” with your other hand. As you lower the “release cylinder” into the middle of
of the aquarium, carefully invert it so that the plexiglas end of the “release cylinder” ends
up on the bottom & center of the aquarium. When the “release cylinder” is on the bottom
of the aquarium, carefully slide the plexiglas out and remove the plexiglas from the
aquarium, leaving the “release cylinder” containing the one test fish “A” in place.
f. For about two or three minutes do nothing else to the aquarium. This will give the fish
some time to acclimate to the situation and will also give the test fish in the “release
cylinder” time to view all areas of the aquarium. Use this 2-3 minutes to be sure each
member of your group knows exactly what she/he is going to be doing during the
experiment once the test fish is released.
g. When you are ready to begin the experiment, slowly lift the “release cylinder” a couple of
inches off of the bottom of the aquarium and then wait for the test fish to swim out of the
cylinder. Then tilt the "release cylinder” slightly and VERY SLOWLY completely
remove it from the aquarium(See the CAUTION below). As soon as the test fish swims
out of the “release cylinder” start timing the experiment and recording data.
CAUTION --- When lifting the “release cylinder” out of the tank DO SO
SLOWLY AND AT A SLIGHT ANGLE. If you were to just pull that cylinder
straight up very fast, the test fish could literally get sucked out of the aquarium.
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h. The experiment consists of recording the amount of time during a 6 minute test period that
the test fish spends in each of the 2 regions of the aquarium. This can get a bit tricky,
especially if the test fish frequently swims from one region to another. Therefore, be sure
you have worked out ahead of time how you will handle such timing.
i. At the end of the 6 minute test period you are to run a replication of this experiment by
doing the following:
(1). Net the test fish from your aquarium and place it in the small tank set aside for
housing the “used” test fish. (It is okay to carry the fish in the net from your table
to the “used” test fish tank; the fish will not be out of the water long enough to be
harmed by such a procedure.)
(2). Fill the “release cylinder” with water from your aquarium, net another test fish
from the appropriate large stock tank, and put the test fish in the “release cylinder.”
(3). Place the plexiglas square over the mouth of the cylinder, and lower the cylinder to
the bottom of the middle of the aquarium, as described in “e” previously, removing
the plexiglas square once the cylinder is on the bottom.
(4). Wait a couple of minutes to give the new test fish in the “release cylinder” a chance
to acclimate to the situation. Then follow the same procedures as outlined in steps
“f-h” previously.
j. When the experimental test and its replication are completed, do the following:
(1). Remove both of the one gallon jars from the aquarium and set them on the bench
top. (Be sure to get one hand under each gallon jar before attempting to lift it
out of the aquarium and be very careful not to bump the jars against the sides
of the aquarium.)
(2). Capture (net) the test fish in the aquarium and return it to the proper “used” test
fish tank.
(3). Holding the net over your aquarium, SLOWLY pour the contents of one of the
gallon jars through the net. This lets all the water return to your aquarium and all
the fish get caught in the net. (Do this carefully so as not to injure the fish.)
Return these fish to the proper stock tank (not to the “used” test fish tank.) Return
to your aquarium and repeat this procedure with the second gallon jar and its
contents.
k. You are now ready to perform some other experiments necessary to fully test Hypothesis I
in order to eliminate the possibility that other factors (variables) besides school size in the
jars caused the results that you found. The procedures will be exactly the same as just
described; all that may change is the number of fish in each gallon jar, the species of fish
being used, or the end of the aquarium in which the jars are placed.
(1). In order to test Hypothesis I (that fish prefer large schools to small schools), you
must determine what control(s) should be run to be compared with the results you
have obtained. (What is a “Control” group? What is an “Experimental”
group?)
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(2). As a group, and in consultation with your instructor, determine what control(s)
need to be run. You may discover that not only is a control necessary, but that more
than one control may be necessary, and even more than one experimental group may
be necessary.
(3). Once you have worked out the control(s) and any other experimental group(s) you
think may be necessary, and have received the “green light” from your instructor,
perform those tests and their replications. (NOTE: It might be wise to figure out
the controls PRIOR to doing any experimentation. This could save you time in
how the manipulations of the gallon jars are to be done.)
D. Experiment B:
Hypothesis II= An individual fish of a schooling species of fish will select
to be a member of (near) a conspecific school, rather than
be a member of (near) a school of heterospecifics.
1. Using the same experimental apparatus as used in testing Hypothesis I, design an experiment
(experiments) and control (controls) to test Hypothesis II. Be sure you have discussed your
tests with your instructor BEFORE proceeding to run the experimental and control
groups.
2. Regardless of the experimental and control groups you decide to run, the procedures will be
the same as discussed in “a- k” for the testing of Hypothesis I. All that may differ are such
things as the species used, numbers used, etc.
WRITING THE LAB REPORT
You are to prepare a formal lab report based on the experimental tests of hypotheses I & II done
during this week’s lab period. Although the experiments are done as a group, each student is to
prepare his/her own lab report as well as construct his/her own graphs. You are encouraged to
discuss the results with members of your group, BUT when it comes time to write the actual lab report,
each student is to do so independently.
In the lab manual, is a handout titled “GUIDELINES FOR WRITING LAB REPORTS.” Be sure to
keep that handout with you while writing your lab report so that you can refer to it often. That handout
does an excellent job of explaining how each of the sections of a lab report is to be written and what
information should be in each section. Follow that handout exactly, except that the information
presented below is in specific reference to the experiments you will do this week and is in addition to
that handout.
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For this first lab report, only include the Hypothesis, Results, Discussion, and Literature Cited
sections.
Hypotheses: These are already stated for you in this lab exercise. (see pp. 6 & 9).
Results:
Tables & Figures
1. All tables and figures (graphs) must be properly formatted. For example, a figure must contain a
figure number, title, labels on the X-axis & Y-axis, and the two axes must be properly calibrated.
Formatting tables and figures is explained in the “GUIDELINES FOR WRITING LAB
REPORTS” and has been modeled for you in the figures and tables in this lab exercise as well
as in last week’s lab exercise.
2. Tables for all raw data and averages are to be in this section.
3. Graphs are to be of the averaged data. For example, since each experiment is run twice,
average those data and then graph them. The graphs may be done by hand, as long as they are
neatly done.
Description of Data
1. Follow the directions in the “GUIDELINES FOR WRITING LAB REPORTS.”
2. Whenever replicates have been done, only describe the averages, unless there are significant
differences between replicates.
Discussion:
1. The “GUIDELINES FOR WRITING LAB REPORTS” does a good job of explaining how to
write this section. FOLLOW THOSE GUIDELINES.
2. The “Conclusions” part of the “Discussion” section needs to be carefully crafted, short, and to
the point. For example, depending on the results from testing hypothesis I, one conclusion
might be a statement such as the following: “The results of this experiment clearly demonstrate
that a conspecific test fish spends most of its time with the school of 10 conspecific fish, rather
than with the school of 2 conspecific fish.”
3. In the “Explanation of Results” part of the “Discussion” section, explain why the results do or do
not support the hypothesis. To do this, direct the reader to the tables and graphs you have
included and carefully interpret for the reader what those data say about the hypothesis tested.
For example, explain how you reached your conclusions from the data and also explain why the
fish behaved as they did.
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Also include some literature that bears on the subject. For example, you should indicate
whether or not your results support the known results in the literature. This will require you to
do some searching for references in the library, although there are some on reserve in the library.
(A list of the references on reserve in the library can be found on pp. 13 & 14 of this lab.)
Use proper literature citations in this section and then proper entries in the “Literature Cited”
section. It is okay to offer conjectures pertaining to why the results do or do not support the
hypotheses tested, BUT be sure it is clear that they are conjectures and that you are not making a
hard and fast statement.
4. In the “Future Experiments” part of the “Discussion” section, explain another experiment that
you think would shed additional light on the results obtained. DO NOT JUST SAY THAT YOU
WOULD REPEAT THE PRESENT EXPERIMENT. Also, propose a new experiment that is not
just intended to support the experiments already done or that merely are changes to experiments
upon which this lab report is based. One way to think about this is to ask yourself the following
question: “Based on the results I obtained in testing the hypotheses, what is the next logical
question to be asked pertaining to schooling behavior in fish?” This section should not be much
more than one paragraph in length.
Literature Cited:
1. Follow the directions given in the “GUIDELINES FOR WRITING LAB REPORTS.”
2. If you are unclear about how to cite literature, talk with your instructor.
Literature Cited
Brooks RL, Yasukawa K. (n.d.). “Schooling behavior in fish.” Laboratory Exercises
in Animal Behavior. http://www.animalbehavior.org/ABS/Educatioon?Lab?index.html (2000,
July20).
Dewsbury DA. 1978. Comparative Animal Behavior. New York; McBraw-Hill Book Company.
(pp. 3-7)
Keenleyside MH. 1975. “Schooling behavior in fish.” Pages 101-104 in Price EO, Stokes AW,
editors. Animal Behavior in Laboratory and Field. New York; W.H. Freeman and Company.
Levine JS, Miller KR. 1994. Biology: Discovering Life. 2nd Ed. Massachusetts; D.C. Health and
Company. (pp.981-986)
Lewis R, Gaffin D, Hoefnagels M, Parker B. 2004. Life. 5th Ed. Boston; McGraw Hill.
Maier R. 1998. Comparative Animal Behavior. Boston; Allyn and Bacon. (pp.327-328).
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Table 1: Results of Testing Hypothesis I that an individual fish of a schooling
species of fish will select to be a member of (near) a large school of
conspecifics, rather than be a member of (near) a small school of
conspecifics.
Aquarium Regions
X End of Tank
# & Species
10A
10A
Seconds
2A
2A
Test Fish
Y End of tank
1A
1A
# & Species
2A
2A
1A
1A
10A
10A
Seconds
Table 2: Results of Testing Hypothesis II that an individual fish of a schooling
species of fish will select to be a member of (near) a conspecific school,
rather than be a member of (near) a school of heterospecifics.
Aquarium Regions
X End of Tank
# & Species
Seconds
Test Fish
Y End of Tank
# & Species
Seconds
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REFERENCES ON RESERVE
Schooling Behavior in Fish
(The following references are on reserve at the main desk in the MC Library. Each of these is on 3
hour reserve, with NO overnight removal. There are also other references in the MC Library that
would be of benefit on the topic of schooling behavior in fish.)
Alexander RD. 1974. The evolution of social behavior. Annual Review of Ecology and Systematics 5:
325-383.
Breder CM Jr. 1967. On the survival value of fish schools. Zoologica: New York Zoological Society
52(4): 25-40.
Drickamer LC, Vessey SH, Meikle D. 1996. Animal Behavior, 4th ed. Dubuque, IA; Wm. C. Brown
Publishers. (Ch. 19 on Evolution of social systems, pp. 353-374).
Griffiths SW, Magurran AE. 1997. Familiarity in schooling fish: How long does it take to acquire?
Animal Behaviour 53(5): 945-949.
Griffiths SW, Magurran AE. 1999. Schooling decisions in guppies (Poecilia reticulata) are based on
familiarity rather than kin recognition by phenotype matching. Behavioral Ecology and
Sociobiology 45(6): 437-443.
Keenleyside MHA. 1955. Some aspects of the schooling behaviour of fish. Behaviour 8: 183-247.
Keenleyside MHA. 1975. Schooling behavior in fish. In Price EO, Stokes AW (editors). Animal
Behavior in Laboratory and Field, 2nd ed. New York; W.H. Freeman and Company, pp. 101-104.
Maier R. 1998. Comparative Animal Behavior: An Evolutionary and Ecological Approach. Boston,
MA; Allyn and Bacon, pp. 327-328 & 335-336.
Niwa H-S. 1994. Self-organizing dynamic model of fish schooling. Journal of Theoretical Biology
171(2): 123-136.
Niwa H-S. 1996. Newtonian dynamical approach to fish schooling. Journal of Theoretical Biology
181(1): 47-63.
Niwa H-S. 1998. School size statistics of fish. Journal of Theoretical Biology 195(3): 351-361.
Peuhkuri N. 1997. Size-assortative shoaling in fish: The effect of oddity on foraging behaviour.
Animal Behaviour 54(2): 271-278.
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Peuhkuri N, Ranta E, Seppa P. 1997. Size-assortative schooling in free-ranging sticklebacks.
Ethology. 03(4): 318-324.
Rowland WJ. 1999. Studying visual cues in fish behavior: a review of ethological techniques.
Environmental Biology of Fishes. 56: 285-305.
Ryer CH, Olla BL. 1998. Shifting the balance between foraging and predator avoidance: the
importance of food distribution for a schooling pelagic forager. Environmental Biology of Fishes
52(4): 467-475.
Shaw E. 1962. The schooling of fishes. Reprinted from: Scientific American, June 1962. California;
W.H.Freeman & Co. pp. 1-10
Slater PJB. 1999. Essentials of Animal Behaviour. Cambridge; Cambridge University Press.
(Ch. 19 on Social organization.)
Williams GC. 1964. Measurement of consociation among fishes and comments on the evolution of
schooling. Publications of the Museum, Michigan State University Biological Series 2(7):
349-382.