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2. energy
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Fish Conservation and
Management
CONS 486
Fish bioenergetics
Diana Chapters 2, 4, 5
Fish bioenergetics topics
• Ration
• Energy fates
• Balanced energy equation
– Scope for growth example
– Budgeting analogy
• MAJOR THEME ALERT! Linking science and
management
Major theme: Linking science to
conservation & management
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Physiology
Behaviour
Population ecology
Ecosystem ecology
Habitat data
(limnology,
oceanography)
• Life history
• Protecting
populations &
habitats
• Restoring
populations &
habitats
Basic science
Applied
science
Conservation
Management
• Fisheries
exploitation data
• Applied life history
data
• Human
dimensions: socioeconomic data
• Harvest regulations
• Managing fisheries
& habitats
Bioenergetics introduction
• Energetics: the study of the processes involved in energy
conversion
• Bioenergetics: the study of energy flow through living
systems
– biochemistry of cellular processes and metabolism
• Energy is a big deal: essential to all biological processes
– Growth
– Development
– Metabolism
• Goal of today: to discuss energy flow, energy fate, energy
budget, and why it all matters!
Rations!
• Energy input is only possible through consumption
of food
– Unlike plants, fish are not photosynthetic! But think of
the possibilities…
• Food consumption is measured as a ration (usually
percent of body weight)
– Typically ranges from 0-7% of body weight
• SURPRISE! Temperature is one of the most
important abiotic features affecting ration
Scope for Growth
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Difference between maintenance and maximum rations
Maintenance ration – min ration so that weight remains same
Maximum ration – max amount of food that can be eaten/digested
When scope > zero, fish are gaining weight
In this example, fish lose weight at temps > 24 °C
Analogous to Scope for Activity (Topt for Scope for Growth – 11-12 C)
Diana fig 5-7
The long arm of the law…
• Animals function as closed systems and follow the
first law of thermodynamics: the conservation of
energy
• Energy cannot be created nor destroyed
– Simply converted from one form to another
– So all energy ingested must be accounted for
Energy fates 1: Waste
• Waste products are eliminated through:
– Egestion (feces and urine)
– Excretion (gill ion exchange)
• The amount of energy eliminated is proportional to
that ingested
– About 20-30%of ingested energy is lost
Energy fates 2: Metabolism
• Standard: rate of energy use by fasting fish at rest
• Active: rate of energy use by fish as a result of
sustained aerobic swimming activity
• Specific Dynamic Action (SDA): costs of processing
of food in the stomach and intestines
– Tends to increase with temperature and quality/quantity
of food
– This can be relatively expensive
• Requiring 12-16% of ingested food to cover its costs
Energy fates 3: Growth
• Growth is simply the synthesis of tissue
– Includes energy diverted to somatic (non-reproductive)
and gonadal (reproductive) tissues
Energy fate
Schematic
(approximate percentages)
SDA
Active Metabolism
Diana fig 2-1
Energy budget
• Partitioning of energy into different uses can
be thought of in terms of a balanced energy
equation
• The equation describes how an animal makes
a living
• How it uses accumulated food energy for:
– Metabolism
– Maintenance
– Growth
– Reproduction
Energy budget
• For an animal to survive, it has to consume at least enough
to account for metabolism and maintenance needs
– For growth and reproduction to occur, it has to have
surplus energy
– Balancing the energy budget is essential for survival and
reproduction
– Thus the equation is shaped by natural selection!
Energy budget (c)
C = Metabolism + Waste + Growth
OR
C = St Met + Act Met + SDA + Eg + Ex + Somatic gr + Gonad gr
SDA
Applying an energy budget: Scope for growth
• Growth is bounded by Cmax (max consumption)
and the sum of all the energetic costs and losses
G = Cmax - M - SDA - Egest- Excret
• Can rearrange to solve for other vars (i.e., C or G)
• Can add additional parameters (e.g., temp, size)
Hartman and Hayward 2006 AFS
G = Cmax - M - SDA - Eg - Ex
• Below is an example of actual sizes of a fish and model predictions of size
• Note how well the bioenergetics model predicts actual growth for any given life
stage or age group
Juvenile European flounder
(Platichthys flesus)
Stevens et al. 2006 J App Ichth
Energy budget prioritization
• Consumed energy is first allocated to
1. Metabolism
– Standard, active & SDA
2. Waste
– Feces and urine
3. Storage (remaining energy only)
– For body growth and/or gonad development
Energy equation analogous to practical economics
• The first costs paid are those for rent or mortgage (metabolism) that
sustain the organism
• The second set of costs (waste losses) are like taxes and they are
proportional to income (food consumption) and must be paid
• Remaining money would be allocated to savings in your bank account
(growth), and if you have enough, you might invest for the future
with stocks/bonds (gonad development)
• If money was limited, future investments would be first sacrificed,
then savings would be second sacrificed; same goes for fish energy
allocation
E=
Ecological and evolutionary context
• Selection favours behaviours that maximize benefits
and minimize costs
– Growth rate or gonad development
• Like an account balance…
– Growth record indicates how the organism resolves the
complexities of its environment!
– Fish otoliths record growth like tree rings
Ohio.gov
Linking science and management
• Many applications of bioenergetics!
• Estimate growth for purposes of aquaculture
• Evaluate impacts of introduced fish on prey or on
competitors or predators
• Studying life history strategies
• Estimate rates of pollution uptake
• Evaluate impacts of changing food resources due to
habitat alteration
• Predicting migration mortality in salmon – in high
flow years they can run out of energy