Download - Behavioural ecology of fishes
BEHAVIORAL ECOLOGY
OF FISHES
outline Introduction
Interactions and behaviours Feeding behaviour Predation Parasitism Mutualism Commensalism Neutralism Migration Communication Camouflaging Mating and spawning behaviour
Introduction
Behavioural ecology is the study of the evolutionary basis for animal behaviour due to ecological pressures.
It also includes the study of Interactions like,
Feeding behaviour, Predation , Parasitism, Mutualism, Commensalim,Neutralism,Migration, Communication,Camouflaging,
Mating and spawning behaviour
Feeding Behavior Feeding behaviour is a complex behaviour that is
closely associated with food intake. Fish have a wide variety of feeding habits and
feeding patterns making them good experimental models for the study of the regulation of feeding behaviour.
Feeding behaviour is regulated by a number of environmental factors and also by complex homeostatic mechanisms that involve central and peripheral hormonal factors as well as metabolites.
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)
Optimal ForagingIt is a model that helps predict how an
animal behaves when it's searching for food. Although obtaining food provides the animal with energy, searching for and capturing the food require both energy and time.
• All else being equal, take the largest prey • Don’t choose prey that takes more energy than it provides •it will Be in a habitat that provides the type of food which is looking for
Finding Food
• Visual detection – Diurnal feeders – Means being in the open in bright light • Olfaction – Common in bottom dwelling species
Predation Most fish species are
simultaneously predator and prey
Very few strict herbivores, detritivores (and young usually are insectivores)
Better predator, more elusive prey
Porcupine fishes
Predator Strong beak/teeth
Prey Spiny covering,
toxins
Barracudas
Predator Sharp teeth
Prey Sleek bodies
Minnows
Predator Pharyngeal teeth
Prey Fear scents
Herrings
Predator Fine gill rackers
Prey Schooling behavior
Predators control prey
Typical situation E.g., largemouth bass control bluegill -
regulate population abundance, size structure
Prey control predators
A typical situation E.g., bluegill in Lake Winona eat bowfin
eggs, young ones, to control the population density.
Prey switching behaviorOptimal foraging theory
Alternate prey present- switch as needed to maximize energy intake vs. energy expenditure
E.g., bluegill - zooplankton, benthos
Intra specific Predation Competition among members of the
same species is known as intraspecific competition,
while competition between individuals of different species is known as interspecific competition.
Cannibalism - bluegill males may consume eggs, young of nest neighbors
Competition competition can be defined as an
interaction between organisms or species, in which the fitness of one is lowered by the presence of another.
Limited supply of at least one resource (such as food, water, and territory) used by both usually facilitates this type of interaction,
although the competition may also exist over other 'amenities', such as females for reproduction (in case of male organisms of the same species).
Food, habitat, mates,etc..
Competition Resource
partitioning via some approach
Behavioral, morphological
E.g., feed in different habitats, or at different times
Character displacement
Alewife invasion(herring) of Lake Michigan shifted ciscoes sp.from planktonic to benthic feeding (and reduced number of gill racers)
Competition Differential exploitation
One species more efficient than another at using a resource
Brown bullhead and pumpkinseed both prefer benthos, but bullhead more efficient
Forces pumpkinseed to switch to zooplankton
Competition
Predation can both decrease and increase competition among fishes
Decrease by reducing numbers so that resources no longer are limiting
Increase by forcing fish together into restricted habitats
Competition
Habitat imprinting may be an evolved behavior to minimize interactions, allowing greater coexistence among species or subspecies
Intraspecific Competition
Size segregation - large adults in different habitats than small adults, juveniles
Large adults occupy habitats with highest benthos densities
Symbiosis
Living together Mutualism, commensalism, parasitism
Symbiosis Sometimes it is used only for cases
where both organisms benefit; sometimes it is used more generally to describe all varieties of relatively tight relationships, i.e. even parasitism, but not predation.
Mutualism - both parties benefit Commensalism - one benefits, the
other receives no benefit or harm Parasitism - one benefits, the other is
harmed
Mutualism
Mutualism is an interaction between two or more species, where species derive a mutual benefit, for example an increased carrying capacity.
Minnows shoaling together in streams, lakes of eastern North America
Mutualism
Cleaning behavior Cleaner wrasses
Commensalism
Commensalism benefits one organism and the other organism is neither benefited nor harmed. It occurs when one organism takes benefits by interacting with another organism by which the host organism is not affected.
A good example is a remora living with a shark. Remoras eat leftover food from the shark.
The shark is not affected in the process, as remoras eat only leftover food of the shark, which does not deplete the shark's resources.
Neutralism
Neutralism describes the relationship between two species that interact but do not affect each other. It describes interactions where the health of one species has absolutely no effect whatsoever on that of the other.
Amensalism
Amensalism is an interaction where an organism inflicts harm to another organism without any costs or benefits received by the other.
Parasitism
Pearl fishes - leave in sea cucumbers Enter body cavity through anus - feed on
gonads One host per lifetime - stays alive
Parasitism
Bitterling - lay eggs into freshwater mussels
Embryos develop from nutrients within gill cavities
Parasites & Pathogens
Major outbreaks and fish die-offs are regular occurrences
Parasites and pathogens most “evolved” if they do not kill their host
Parasite Generalities
Pelagic fishes tend to have fewer parasites than benthic, near shore species (snails, copepods)
Bigger fish have more parasites (numbers and types)
Fish Migration
• 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
Shoaling and its characteristics Shoal - any group of fishes that
remains together for social reasons School - a polarized, synchronized
shoal (has coordinated, directed movements)
Requires great deal of coordination among individuals in the school
Vision is primary sensory cue for coordinating movement
individual movement is coordinated with movement of some other visually distinctive object - e.g. a spot or a stripe
Benefits of Shoaling
• Gives a predator many moving targets – Confuses predators
– Increases food finding ability • Keeps potential mates in close proximity
•It is the mechanism to escape from predation.
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.
• Being dark on top, light on bottom – Look like substrate from above – Look like water surface from below
Eye Spots
• Usually at base of caudal fin – Usually used to confuse predators • Common in some fry – Sometimes used for species recognition
Lateral Stripes
• Mid-lateral band usually • Best developed in schooling fish – Keep school oriented while confusing predators – Makes it hard to pick out individuals
Auditory Signals
• Most fish produce sounds • Uses for sound – Courtship singing – Territorial defense – Signaling shoal
Sound Production
• Stridulation – Rubbing hard surfaces together – Low frequency sounds • Vibration of swimbladder – Can give loud croaking • Incidental to other activities
Chemical Signals
• Pheromones released into the water – Reproductive cues – Recognition • Schreckstoff = fear scents – Predator avoidance – Produced in epidermal cells
Refrences
http://en.wikipedia.org/wiki/Behavioral_ecology
Behaviour of fishes-A N Shukla. http://en.wikipedia.org/wiki/
Biological_interaction#Neutralism
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