Schooling of Fish:
Advantages and
Disadvantages of the
Buddy System
Taylor Drexinger
Lena Finkel
David Quinn
Caroline Wilkinson
Background
• Schooling vs. Shoaling
• How fish school
• Both advantages and disadvantages
Relevance
• Impact on surrounding species
• Impact on surrounding environment
What Fish School
• Clupeomorpha
• Barracuda
• Larvae
• Some sharks (hammerheads)
• Ostariophysi
Advantage-Social
• When separated from the school, the individuals
become skittish and aggressive
• Lower respiration rate when fish in groups
• Synchronized actions
Advantage-Reproductive
• Easier to find mate
• Decreases chance of larval predation
• Initiation of schooling from environmental factors after
morphological evolution
Advantage-Foraging
• More eyes to seek prey
• Copepods and herring
Advantage-Hydrodynamic
• Schooling placement is not
random
• Draft off of each other
• Back and forth tail movement
“wagging”
Advantage-Predator avoidance
• Reduce probability of capture
• Reduced ease of capture
• Improved detection of
predatory threats
How does schooling decrease risk of
predation?
• 1/N Hypothesis
• Confusion Hypothesis
• Predator Satiation Hypothesis
• Predator Detection
1/n Hypothesis
• Based on a simple mathematical model
P = 1/n
Where a schooling fish’s probability of being consumed by a
predator (P) is function of the size of the school (n)
• Obviously a gross simplification (basic form assumes
predators only consume one prey item per feeding)
• Nevertheless, useful in describing the basic theoretical
relationship between school size and risk of predation.
Confusion Hypothesis
• Schooling may allow fish to exploit perceptual bottlenecks
within a predator’s nervous system, by overwhelming its
ability to process visual and auditory signals.
• Predators unable to isolate/maintain
individual prey
focus on
• results in “relay race” effect, in which predator follows a
prey target for a short time before diverting its attention to
a different target… overall predation reduced as attacker
constantly pursues new prey targets with little success.
• In theory the confusion effect on predator should increase
with relative school size of the prey
Confusion Hypothesis
Vs.
Works on humans too!
Predator Satiation Hypothesis
• There is a maximum amount of prey an
individual predator can consume during an
individual feeding
• By synchronizing behaviors amoung large groups
of individuals, prey fishes can exploit the
inability of predators to consume more than a
set amount of prey… ensures the survival of the
remaining fish
• The Predator Satiation Hypothesis may explain
the synchronized and social behavior of wide
range of other organisms throughout the
Synchronous
Emergence
of Adult
Mayflies from
Larval Stage
Synchronous Acorn
Production Among
Adjacent Oak Trees
Mass Nesting
in Sea Turtles
Predator Detection Hypothesis
• Larger schools… wider collective field of vision
• One hole: schooling obscures vision of individuals located
near the interior of the group
• Possible association with alarm substances to provide net
advantage…. See Ostariophysi
Disadvantages – Ease of Predation
• Easy for underwater predators to spot because of size
• Birds can easily spot large bait balls near the surface
• Normally attracts a lot of birds, not just one
• Cannot effectively hide in reefs or underwater structures
• Move around constantly due to resource demands
• More chances to run into prey
• Whale’s size negate most anti-predator measures
Disadvantages – Concentration of
Pollution
• Very similar to aquaculture disadvantages
• Disease spread quick due to proximity
• Waste is concentrated
• One sick fish can put the entire school at risk
•
•
•
One fish gets out of rhythm
Loses main anti-predator behavior caused by
synchronous movements
Predators can begin to pick off the school
Disadvantages – Use of Resources
• Must move on quickly to new food sources
• Food found during foraging used up
•
quickly due to sheer number of fish
Can get very little food depending on
orientation in the school
• Use large amounts of dissolved oxygen
Predator Adaptations
• Adopted their own schooling behavior
Will yield very high returns especially for predators in
front of the pack
• Sailfish, Dolphins
•
• Force schools into shallow or cluttered waters
• Mass synchronous movement greatly hindered
• Specific adaptations
• Spinner Shark, Sailfish, Swordfish, Thresher Shark
Still, certain questions remain unanswered…
…What aspects of a predatory stimulus actually elicit a
behavioral/defensive response?
…How do schooling patterns change in response to a predatory
attack?
…Who shot Biggie Smalls?
Conservation
•
•
Quantitative analysis of fish schooling can lead to
o better commercial fishing practices
o information on environmental demands for large schools
Better understanding for efficient aquaculture of schooling
fishes
o Resources demand (ex. Oxygen levels)
o Need for Waste Removal
o Combating diseases
Future Research
Windmills!
Summary
• Advantages
• Disadvantages
• Hypotheses
Evaluation of Sources
• Valid conclusions
• Experimental data
• Dated in some cases
References
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Barber, I., & Huntingford, F. A. (1996). Parasite infection alters schooling behaviour: deviant
positioning of helminth-infected minnows in conspecific groups. Proceedings of the Royal Society of
London. Series B: Biological Sciences, 263(1374), 1095-1102.
Bertrand, A., Barbieri, M. A., Gerlotto, F., Leiva, F., & Córdova, J. (2006). Determinism and plasticity
of fish schooling behaviour as exemplified by the South Pacific jack mackerel Trachurus
murphyi. Marine Ecology Progress Series, 311, 145-156.
Eggers, D. M. (1976). Theoretical effect of schooling by planktivorous fish predators on rate of prey
consumption. Journal of the Fisheries Board of Canada, 33(9), 1964-1971.
Major, P. F. (1978). Predator-prey interactions in two schooling fishes,< i> Caranx ignobilis</i> and< i>
Stolephorus purpureus</i>. Animal Behaviour, 26, 760-777.
Ryer, C.H., and B.L. Olla. 1991. Information transfer and the facilitation and inhibition of feeding in a
schooling fish. Environmental Biology of Fishes 30.3: 317-323.
Abrahams, M., Colgan, P. 1985. Risk of predation, hydrodynamic efficiency, and their influence on
school structure. Environmental Biology of Fishes. 13.3: 195-202.
Partridge, B., Pitcher, T., Culler, M., Wilson, J. 1980. The three-dimensional structure of fish schools.
Behavioral Ecology and Sociobiology. 6.4:277-288.
References
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Kils, U. 1992. The esSCOPE and dynIMAGE: Microscale tools for in situ studies of predator-prey
interactions. Arch Hydrobiol Beih 36: 83-96.
Moyle, P.B., Cech, J.J. 2003. Fishes, An introduction to Ichthyology. 5th Ed. Benjamin Cummings.
Hunter, J.R., Coyne, K.M. 1982. The onset of schooling in northern anchovy larvae, Engraulis
mordax. CalCOFI 23: 246-251.
Landa, J.T. 1998. Bioeconomics of schooling fishes: selfish fish, quasi-free riders, and other fishy tales.
Environmental Biology of Fishes. 53.4:353-364.
Alexander, R.M. 2004. Hitching a lift hydrodynamically- in swimming, flying and cycling. Journal of Biology.
3.2:7.
Weiner, Jon. "Ideas for Wind Farming."California Institution of Technology News. CalTech University, 17 May
2012. Web. 25 Nov. 2012. <http://www.caltech.edu/content/schooling-fish-offer-new-ideas-wind-farming>.
Images
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http://www.sharkattackfile.net/species.htm#spinner
http://www.extremescience.com/sailfish.htm
http://dsc.discovery.com/sharks/shark-pictures/pelagic-thresher-shark.html
http://natural-wild-life.blogspot.com/2011/09/barracuda.html