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)• 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

• 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

Okinawa rubble goby

Trimma okinawae

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 Patterns

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

Three-spined stickleback Gasterosteus aculeatus

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.

Synodontis punctatus

Haplochromis nubilus

Learning• 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)

Halichoeres garnotiYellowhead wrasse

Use of a rock as an anvil Coyer, 1995

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

Cognition

• 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

Migration

Migration

• Spatial orientation and mapping– Migration: Piloting, orientation

(directional headings), navigation (relative location)

– The role of learning in migration– (magnetite, light, etc..)

Reproductive behavior

• Sexual selection– Courtship– Female choice– Male aggression

• Leks

Pseudotropheus zebra

Lake Malawi

male

female

Mating strategies

• Promiscuous• Monogamous• Polygamous: polygynous, polyandrous

• Certainty of paternity matters!

Multiple paternity

Hexagrammos decagrammus Kelp Greenling

Hippocampus barbiganti Pigmy seahorse

Trumpetfish / herbivores

Symbiosis

Clownfishes / Anemones

Vendellia cirrhosa

Urinophilus diabolicus

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

• 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

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

Fish Migration

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

Timing of migrations

– Annual – Daily – generational

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

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

Orientation During Migration

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

Disadvantages of Migrations

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

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

• 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 & Communication

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

Definitions

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

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

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

• Hydrodynamic efficiency

• Reduced predation risk

• Feeding

• Reproduction

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 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 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 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 & 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 & 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

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

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

• 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

• 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

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

Agressive Behavior

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

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

• 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)

Communication

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

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

• 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

• 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

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

Common Color Patterns

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

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

• 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

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

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

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

Eye Ornamentation

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

EyeEye Spots Spots

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

LateLateral Strral Stripesipes

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

• Dominant members are often more brightly colored Dominant members are often more brightly colored

– Makes it easier to attract mates – Makes it easier to attract mates

– But, makes them more conspicuous to predators– But, makes them more conspicuous to predators

Auditory SignalsAuditory Signals

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

Sound ProductionSound Production

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

Chemical Signals Chemical Signals

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

Electrical SignalsElectrical Signals

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

Photo used with permission of Dr. Craig S. Kasper

Dr. Craig S. KasperAquaculture Program ManagerHillsborough Community College10414 E. Columbus Dr.BSCI 207ETampa, FL 33619-7856Phone: 813-253-7881FAX: 813-253-7868Email: ckasper@hccfl.edu