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Fish Behavior. Animal Behavior. Action or re-action to stimuli Happens in the brain (non-motor) and can be manifested through muscular response, but often involves both There can be a temporal component to the actual behavior (learning, e.g. feed training)

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Fish Behavior

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Fish behavior

Fish Behavior

Animal behavior

Animal Behavior

  • Action or re-action to stimuli

  • Happens in the brain (non-motor) and can be manifested through muscular response, but often involves both

  • There can be a temporal component to the actual behavior (learning, e.g. feed training)

  • Short-term trigger for behavior, or effect on the organism

  • Long-term evolutionary significance/adaptation: behavior is selected for.

  • Animals behave in ways that maximize their fitness

Genetic vs environmental factors

Genetic vs environmental factors

  • Nature/nurture? On-going debate

  • Behaviors have phenotypic variation: studies on problem solving

  • Due in part to genetic propensity: ‘ability’ to learn

  • Due in part to environmental pressures and variability

  • The two: genes and environment, work in concert

  • Innate behavior: less subject to environmental variation. Developmentally fixed

Genetic and environmental components of behavior a case study

Genetic and environmental components of behavior: a case study

Okinawa rubble goby

Trimma okinawae

Fixed action patterns

Fixed Action Patterns

Fixed Action Patterns: stereotypical innate behavior. The organism will carry it out almost no matter what, even if it doesn’t seem appropriate. These are all part of a category of behaviors very important to survival and/or fitness.

Fixed action patterns1

Fixed Action Patterns

Male three spined stickleback: attacks other males with red bellies – attacks anything red

Three-spined stickleback

Gasterosteus aculeatus

Innate behavior

Innate behavior

  • Brood parasitism is a classical example (Cichlid/catfish)

  • Ability to confront novel stimuli, learn about them and adjust behavior is indicative of intelligence and self awareness. Intelligence is ‘costly’: brain development, parental investment etc.

Fish behavior

Haplochromis nubilus

Synodontis punctatus



  • Change in behavior based on experience

    • Maturation is behavior change based largely on ability due to development (eg. Use of tool)

  • Habituation

    • Loss of responsiveness due to repetition

  • Imprinting

    • Learning in a critical time period (tightly correlated with innate behavior) (e.g. bluehead wrasse young females, salmon inprint on stream)

  • Conditioning: Pavlov

    • Associating a stimulus with punishment or reward (can also be trial and error) (visual experiments)

Fish behavior

Use of a rock as an anvil

Coyer, 1995

Halichoeres garnoti

Yellowhead wrasse

Associative learning conditioning

Associative learning/conditioning

  • Associating one stimulus with another

  • Pavlov: classical conditioning. Associating an arbitrary stimulus with reward or punishment

  • Operant conditioning: learning through trial and error. BF Skinner’s experiments. This has formed the basis for much animal training.

  • Classical and operant conditioning often work together



  • Problem solving studies

  • Consciousness and awareness

  • The connection between nervous system function and behavior

  • Spatial orientation and mapping

    • Migration: Piloting, orientation (directional headings), navigation (relative location)

    • The role of learning in migration

Fish behavior




  • Spatial orientation and mapping

    • Migration: Piloting, orientation (directional headings), navigation (relative location)

    • The role of learning in migration

    • (magnetite, light, etc..)

Reproductive behavior

Reproductive behavior

  • Sexual selection

    • Courtship

    • Female choice

    • Male aggression

  • Leks

Fish behavior


Pseudotropheus zebra

Lake Malawi


Mating strategies

Mating strategies

  • Promiscuous

  • Monogamous

  • Polygamous: polygynous, polyandrous

  • Certainty of paternity matters!

Fish behavior

Hexagrammos decagrammus

Kelp Greenling

Multiple paternity

Fish behavior

Hippocampus barbiganti

Pigmy seahorse

Fish behavior


Trumpetfish / herbivores

Fish behavior

Clownfishes / Anemones

Fish behavior

Vendellia cirrhosa

Urinophilus diabolicus

Behavioral ecology

Behavioral ecology

  • Animals behave in ways that maximize their fitness

    • Reproductive behavior = more successful offspring

    • Feeding behavior = maximum energy gain

  • Research examples:

    • Sparrows and cuckoldry

    • Cheetahs and prey selection

    • Elephant seals and polygyny

    • Humpback whale songs

Feeding behavior

Feeding Behavior

  • Example - Sunfish, provide predator with prey of different sizes and different densities, fish respond by foraging optimally (taking the most energetically rich prey under the appropriate conditions)

Fish behaviors

Fish Behaviors

• Migration • Shoaling • Feeding • Aggression • Resting • Communication  

Fish migration

Fish Migration

• Fish migrations are usually round-trip • Reasons for migration – Food gathering – Temperature adjustment – Breeding

Timing of migrations

Timing of migrations

– Annual – Daily – generational

Classification of fish migration

Classification of Fish Migration

  • Diadromous – Travel between sea & fresh water

    – Anadromous – most of life at sea, breed in fresh water – Catadromous – most of life in fresh water, breed at sea – Amphidromous – migrate between water types at some stage other than breeding

    • Potamodromous – Migrate within a fresh water system

  • Ocenodromous – Migrate to different regions of the ocean

Reasons for migrations

Reasons for Migrations

• Take advantage of different habitats – Feeding – Protection • Avoid adverse conditions • Meet requirements for reproduction

Orientation during migration

Orientation During Migration

• Orientation to gradients of temperature, salinity, and chemicals • Orientation by the sun • Orientation to geomagnetic and geoelectric fields

Disadvantages of migrations

Disadvantages of Migrations

• Expenditure of energy – Most must store energy before migration • Risk from predation

Adjustments required due to migrations

Adjustments Required Due to Migrations

• Adjusting physiologically to new water conditions – Temperature – Light – Water chemistry • Many migratory species are now rapidly declining due to changes caused by man

Fish behavior communication

Fish Behavior & Communication

  • Comparison of Migrations • Some stream species migrate a few yards from feeding to spawning grounds • Some species travel hundreds of miles just to spawn

Fish behavior communication1

Fish Behavior & Communication

  • Shoals and Other Aggregations • Forms of fish grouping – Solitary – Shoal – School – Pod • Reasons for grouping – Traveling – Feeding – Dealing with predators – Reproduction



  • Shoal - any group of fishes that remains together for social reasons

  • School - a polarized, synchronized shoal (has coordinated, directed movements)

How do schools work

How do Schools Work?

  • Requires great deal of coordination among individuals in the school

  • Vision is primary sensory cue for coordinating movement

  • Use of optomotor reaction - individual movement is coordinated with movement of some other visually distinctive object - e.g. a spot or a stripe

Functions of schooling behavior

Functions of Schooling Behavior

  • Hydrodynamic efficiency

  • Reduced predation risk

  • Feeding

  • Reproduction

Functions of schooling behavior1

Functions of Schooling Behavior

  • Hydrodynamic efficiency

    • individuals obtain reduction in drag by following in “slip-stream” of neighbors

    • limited evidence in support of this

Functions of schooling behavior2

Functions of Schooling Behavior

  • Reduced predation risk

    • creates patchy distribution of prey - large areas with no prey

    • once school is found, individual risk of being captured is reduced by dilution

    • confusion of prey by protean displays, encirclement, other behaviors

Functions of schooling behavior3

Functions of Schooling Behavior

  • Feeding

    • increases effective search space for the individual (more eyes, separated by greater distance)

    • coordinated movements to help break up schools of prey - analogous to pack behavior in wolves - by tunas, jacks

Functions of schooling behavior4

Functions of Schooling Behavior

  • Reproduction

    • increases likelihood of finding a mate

    • facilitates coordination of preparedness (behavioral and pheromonal cues)

    • facilitates arriving at right spawning site at right time

Fish behavior communication2

Fish Behavior & Communication

  • Shoaling • A social grouping of fish • Occurs throughout life in about 25% of fish species • Half of all fish shoal at some time

  • Benefits of Shoaling • Gives a predator many moving targets – Confuses predators – Increases chances at the individual level – Increases food finding ability • Keeps potential mates in close proximity

Fish behavior communication3

Fish Behavior & Communication

  • Pods • Tightly grouped school • Move as a single unit (including making quick turns) • Makes the school appear like one large organism – Protection from predators

Liabilities of grouping behavior

Liabilities of Grouping Behavior

• Increased likelihood of disease & parasite transmission • Becoming more conspicuous to some predators – Harvested more easily by man

Feeding behavior1

Feeding Behavior

• Morphology is often a key to feeding behavior – many fish have specialized habits • Actual feeding may depend on what is available

• Optimal foraging – Take whatever is closest, as long as it is suitable food – Highest quality of food for the least amount of effort

Optimal foraging

Optimal Foraging

• All else being equal, take the largest prey • Don’t choose prey that takes more energy than it provides • Be in a habitat that provides the type of food you are looking for

Risk sensitive foraging

Risk Sensitive Foraging

• Foraging is sometimes restricted because of undo risk – It does not make sense to look for prey where you will become the prey – Must balance energy gain possibility with risk of obtaining the energy

Finding food

Finding Food

• Visual detection – Diurnal feeders – Means being in the open in bright light • Olfaction – Common in bottom dwelling species • Taste

Agressive behavior

Agressive Behavior

• Direct charges – Often includes biting • Ritualistic displays – Modified swimming – Flaring gill covers – Color changes – Threatening movements

Reasons for aggressive behavior

Reasons for Aggressive Behavior

• Defense of territory – Usually connected with reproduction – Sometimes to keep food source • Defense of brood • Repelling competitors for mates

Resting behavior

Resting Behavior

• Inactive state• Some fish spend a large part of the day not doing anything • Many species change color patterns • Most fish rest on or near the substrate • Many fish have a specified time of day when resting takes place • Some fish never rest (Sleep swimming?)

– Must keep moving (sharks)



  • Visual signals • Auditory signals • Chemical signals • Electric signals



  • Visual Signals • Most important communication signal • Large variety of signals – Different species use different “languages” – Some cues are recognized between species

How visual signals are produced

How visual signals are produced

• Types of coloring – Pigments • Colored compounds • Located in chromatophores – In mostly in skin, but also in eyes & organs • Controlled by hormones & nerves – Structural colors • Reflection of light

Kinds of pigments in fish

Kinds of Pigments in Fish

• Carotenoid pigments – Bright reds & yellow – Green when they overly blue structural color • Melanins – Dark red, brown, black • Purines (guanine) – Colorless crystals responsible for some structural colors

Purpose of color patterns

Purpose of Color Patterns

• Thermoregulatin – Probably not very significant • Intraspecific communication • Evasion of predators

Common color patterns

Common Color Patterns

• Red coloration • Poster colors • Disruptive colors • Countershading • Eye ornamentation • Lateral stripes • Polychromatism

Red coloration

Red Coloration

• Red fish are common • Cryptic color in low light • Blends in to red algae • Used in spawning fish – Recognized at short distances – Does not attract predators at long distance

Fish behavior

Poster Colors

• Bright, complex color patterns – Some fish use this to advertise when protecting territories – May serve to signal shoal – In some cases it may be used for predator avoidance • Blending into a complex background – Flash effect to avoid predators – May serve as a warning to others

Fish behavior

Disruptive Coloration (Camo!)

• Disrupt the outline of the fish – Make them less visible – Often associated with beds of plants

Also known as “protective resemblance” or “aggressive resemblance”...depends on state of animal.

Fish behavior


• Being dark on top, light on bottom – Look like substrate from above – Look like water surface from below

Eye ornamentation

Eye Ornamentation

• Either to disguise the eye or emphasize it – Disguising the eye • Minimize contrasting color • Field of spots around eye to disguise pupil • Eye lines that match pupil – Emphasizing the eye • Pattern or colors in eye • Usually used for interspecific signaling

Eye spots

Eye Spots

• Usually at base of caudal fin – Usually used to confuse predators • Common in some fry – Sometimes used for species recognition

Late ral str ipes

Lateral Stripes

• Mid-lateral band usually • Best developed in schooling fish – Keep school oriented while confusing predators – Makes it hard to pick out individuals

Fish behavior


• Dominant members are often more brightly colored – Makes it easier to attract mates – But, makes them more conspicuous to predators

Auditory signals

Auditory Signals

• Most fish produce sounds • Uses for sound – Courtship singing – Territorial defense – Signaling shoal

Sound production

Sound Production

• Stridulation – Rubbing hard surfaces together – Low frequency sounds • Vibration of swimbladder – Can give loud croaking • Incidental to other activities

Chemical signals

Chemical Signals

• Pheromones released into the water – Reproductive cues – Recognition • Schreckstoff = fear scents – Predator avoidance – Produced in epidermal cells

Electrical signals

Electrical Signals

• Muscle contractions give off a weak -Some fish have electric producing organs – Used to locate prey or conspecifics

Fish behavior

Dr. Craig S. Kasper

Aquaculture Program Manager

Hillsborough Community College

10414 E. Columbus Dr.


Tampa, FL 33619-7856

Phone: 813-253-7881

FAX: 813-253-7868


Photo used with permission of Dr. Craig S. Kasper

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