Manipulating Fish Behaviour
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Transcript Manipulating Fish Behaviour
FBE201: Summer 2012
Manipulating Fish Behaviour
Introduction
• Economically driven culture systems attempt
to maximize yields by maintaining fish at high densities,
minimizing husbandry requirements
keeping the fish farm environment as
basic as possible
using feeds which are artificial both in
appearance and composition
Introduction
• Some aspects of natural behaviour of the fish
are retained and there are changes in
behaviour
• Either improvement or optimization of
efficiencies could be expected.
• Integrating the behavioural requirements of a
culture species with other biological aspects
of the management protocols
Environmental control
Cage/tank design
• Constrain swimming behaviour of fish in the farm
environment
• Square cages slow fish down as they adjust their
course when encountering corners
• Circular cages may enhance schooling behaviour
and uninterrupted swimming action
• Practical considerations of cages should join
together in a more cost-effective way (i.e. units of
square or rectangular cages).
Environmental control
Cage/tank design
• Reduce surface exposure by high-density
feeding strategies or the development of subsurface feeding.
• Provide cages with shading for a more effective
utilization of cage volume
• Artificial lighting is a general modifier of
behaviour, like foraging, sexual maturation,
nocturnal schooling
Environmental control
Water quality
• Farmed fishes exhibit strong thermal
behaviour, by maintaining relatively constant
body temperatures
• Temperature; maximize food conversion and
growth
• Temperature & salinity; influence position in
water column
Feeding patterns
• Any feeding protocol seeks to optimize FCR
through the modification of feeding regimes, and
by maximizing the amount of food being taken,
thereby minimizing waste.
• Commercial feeding schedules through daylight
hours
• Diel rhythmus apparently driven by photoperiod
• Strongly influenced by temperature variation
• May cause a switch from diurnal to nocturnal
feeding pattern.
Feeding patterns
Presentation control
• Spatial and temporal distribution
• Hand-feeding, where a visual judgment of fish
behaviour is used to assess hunger level.
• Most farmed fish species show an adaptive
flexibility in their feeding behaviour.
• Demand feeders are controlled by the feeding
behaviour at either the individual or the group
level.
• Self-feeders are so termed because they rely on
the individual feeding activity of the fish
actuating a manual or electronic trigger.
Feeding patterns
Dietary characteristics
• Visual characteristics such as shape, size,
colour and movement,
• Gustatory properties such as texture, taste
and smell.
• Artificial diet capture and ingestion can be
improved by enhancing the fish’s visual
perception of pellets
Feeding patterns
Dietary characteristics
• Fish offered diets which contrast well with
background colours will capture proportionately
more pellets and, as a result, grow faster.
• Shape may also be of importance, but
manipulating shape will also affect the movement
profiles of pellets through water.
• Long pellets tend to tumble in the water column,
whereas round ones sink much faster in a rolling
motion.
Feeding patterns
Dietary characteristics
• Addition of gustatory stimulants (e.g. proteins,
amino acids, vitamins, minerals, fish oils) to
diets, enhance the dietary perception of a
pellet.
• Other dietary constituents can be used as
chemo-attractants, enhancing both attraction
and taste, and several amino acids now
incorporated in to commercial diets for these
reasons.
Feeding patterns
Photpperiod
• If the fish are reliant on visual stimuli then the
photoperiod provides a finite window for
feeding but it also contributes information
relating to time of day and time of season.
• Continuous illumination has effect on
schooling behavior and sexual maturation.
• It also can provide enhance feeding times,
resulting in faster growth rates.
Feeding patterns
Dominance regulation
• Social hierarchy formation may lead to depressed
feeding in subordinates, resulting in growth
suppression.
• Temporal (localized) feeding enables domination
of some fish over lower ranking individuals
• Rate of aggression increase as the number of fish
per tank or cage increase
• Adoption of a feeding protocol combining a high
fish density and moderate food dispersal within
limits