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Fish Behaviour > Final > Flashcards

Final Flashcards

1
Q

Why is temperature important for animals?

A

-biological processes are based on temperature
-proteins function at different rates depending on temp
-chemical and physical properties of water change based on temp (oxygen sat., sold holding capacity, etc.)

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2
Q

why are warm water fish so important?

A

-for fisheries: higher numbers of species and density means easer to catch and feed more people, high catch for low effort
-for aqua: 4 of the 5 top aqua species are warm water and 9 of the 10 top fish groups, most aqua happens close to equator

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3
Q

what does temperature have a large effect on for fish?

A

-growth and feeding rate
-development
-lifespan
-reproduction

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4
Q

what is important to consider for optimizing fish health and growth when it comes to temperature?

A

-effects of temp changes: qualitative factors (metabolic impacts) and quantitative (Q10 effects)
-thermal tolerance: max and min temp in which fish can thrive, function, and reproduce

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5
Q

what are the two ways of classifying thermal biology?

A

-source of body heat (endo or ecto)
-temp variability tolerance: (poikilo and homeo)

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6
Q

what are endo-, ecto-, poikilo-, and homeotherms?

A

-endo: internally produced heat is used to maintain body temperature (regulate)
-ecto: environment determines body temperature (tolerates)
-poikilo: tolerates parable body temperature over a timeframe (doesn’t need controls)
-homeo: needs stable temperature (needs control)

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7
Q

what are the thermal strategies of polar and tropical fish?

A

homeothermic ectotherms: environment is stable temp so they don’t need to have wide tolerance, can invest energy elsewhere

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8
Q

what are the majority of amphibians, reptiles, fish, and invertebrates thermal strategies?

A

poikilothermic, ectotherms

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9
Q

what are tuna, moonfish, and some sharks thermal strategies?

A

poikilothermic, endotherms: they are hight migratory so they need to adjust their temp over drastic temp changes and can use heat they produce to swim fast (regional endotherm- in one area of the body)

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10
Q

what is the thermal strategy for most birds and mammals?

A

homeothermic endotherm

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11
Q

why is it easier to be a large endotherm?

A

they have smaller surface area to volume ratios so they lose less heat to the environment than smaller animals (have large surface areas to volume and must use much more energy to produce enough body heat to maintain stable internal temperatures)

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12
Q

why is it easier to be an endotherm in air vs water?

A

air takes much less energy to heat and takes less heat away

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13
Q

what is the thermoneutral zone for endotherms?

A

temp at which there’s no thermal stress, no mechanisms are initiated to remain normothermic

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14
Q

what is the lower and upper critical limit for endotherms?

A

-lower: point at which mechanism will kick in to keep animal warm - metabolic heat production (shivering, sleeping, etc.)
-upper: mechanism will kick in to keep animal cool - evaporative cooling (sweating, panting, etc.)

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15
Q

what are normothermia, hypothermia, and hyperthermia?

A

-normo: tolerable temp range (between lethal limits)
-hypo: animal is too cold - environment has decreased animals temperature (past lower lethal limit)
-hyper: animal is too warm - environment has increased animals temp. (past upper lethal limit)

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16
Q

for ectotherms, what replaces the thermoneutral zone and upper and lower lethal limits?

A

-range of optimum performance
-incipient lower and upper lethal limits (highest and lowest survivable temperatures

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17
Q

what are some performance indicators for performance optima?

A

-reproduction
-prey capture
-BMR
-FCR
-growth

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18
Q

what is metabolism?

A

the cost of living, energy consumed/time unit
-measured by oxygen consumption or heat production

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19
Q

why can ectotherms grow faster than endotherms?

A
  • can put more energy into growing since they don’t have to spend energy regulating body temp
    -dont need specific tissues to retain heat
    -dont need to fight gravity so don’t need as dense bones and can build more muscle instead
    -these reasons give them good FCR’s
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20
Q

what is characteristic of a homeothermic ectotherm?

A

-not adapted to changes in body temp (narrow temperature tolerance)
-poorly when internal temperature changes
-small performance optima
-use performance optima graph to assess
-ex. ice fish

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21
Q

what is characteristic of a poikilothermic ectotherm?

A

-adapted to changes in internal temp (broad range)
-assessed by thermal polygon for temperature profile because they have a range of tolerance
-shock only occurs if acclimation is not allowed

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22
Q

what is acclimation?

A

short term introduction of different temp

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23
Q

what is acclimatization?

A

long-term more gradual introduction of a difference temperature

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24
Q

why is there diversity of thermal biology?

A

-dirven by challenges (natural selection)
-filling niches
-ancestral states

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25
Q

what are the two types of thermal tolerances?

A

-eurythermic: wide range of temp (adapt well to large seasonal change, occupying broach range of niches, can weather catastrophic events - rapid change), thermal tolerance polygon is large
-stenothermic: narrow range of ambient temp at a time, rapid changes aren’t tolerated but can acclimate, small thermal tolerance polygon

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26
Q

in a thermal tolerance polygon, where does feeding, reproduction, and severe vs less challenging climate survival fit?

A

-feeding: inside regular tolerance
-reproduction- very narrow range of temps
-severe: short amount of time
-less severe: longer

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27
Q

what does Q10 measure?

what can it tell you/used for?

A

-rate of change a biological or chemical system experiences because of increasing temp by 10 degrees
-effect of temp on function
-can tell you if you need fixed thermal conditions
-used for preparing species for release

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28
Q

what Q10 do most biological processes have?

A

between 2 and 3

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29
Q

what is the biggest reason fish die?

A

oxygen limitations

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30
Q

what is the partial pressure of gas?

what does it control

A

driving force for gas in liquid
-controls amount of gas that’s dissolved into the liquid

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31
Q

what is the total amount of gas able to be dissolved in liquid set by?

A

solubility of the gas and the temp of the liquid (total gas pressure %)

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32
Q

what is total barometric pressure?

A

sum of all partial pressure of each gas n a mix

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33
Q

what is atmospheric pressure at sea level?

A

755 Hg (20.9% oxygen, 78.1% nitrogen, 0.03% co2)

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34
Q

what effect does temperature have on oxygen saturation of water?

A

as temp increases, less oxygen can be absorbed (100% oxygen decreases) because of movement of water molecules increasing due to increased temperature which knocks them out of the water into vapour

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35
Q

how does salinity affect oxygen saturation?

A

the higher the salinity, the less oxygen because salt molecules take in space I the water

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36
Q

what is responsible for loading oxygen into the blood?

A

-partial pressure gradients, even when there’s less oxygen in the water, the partial pressure in the blood is always lower so oxygen will always be pushed in

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37
Q

at the same partial pressure, how does air differ from water? what about cold vs warm water? what about freshwater compared to SW

A

-ar has more oxygen
-colder water has more oxygen
-FW has more oxygen

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38
Q

what are the reasons gills are so efficient?

A

-lamellae: pick up oxygen and bring it to capillaries where its taken to rest of body, have phenotypic plasticity meaning they can be filled when oxygen is high so not too much oxygen is taken up or exposed when oxygen is low
-counter-current flow: blood flows in opposite way water does so that equilibrium between partial pressure of oxygen in water and blood won’t ever be reached because blood will always have less oxygen than water flowing past
-need less of a partial pressure gradient to load blood
-better extraction of oxygen from water in gills compared to lungs in air

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39
Q

what is the oxygen cascade?

A

the path that oxygen takes moving through the body to be consumed by tissues

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40
Q

why do water breathers need to be more efficient at obtaining oxygen?

A

-harder to get the same level of oxygen into tissue from water because oxygen moves slow in water so a big partial pressure gradient is needed to move oxygen
-need to overcome low oxygen and higher viscosity

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41
Q

why is the partial pressure of oxygen in the blood lower than the water even though there is more oxygen in the blood?

A

-most of the oxygen in the blood is taken out of the equation because most of it s out of solution, bound with hemoglobin

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42
Q

what is hemoglobin?

A

-a protein that binds oxygen in red blood cells
-almost all vertebrate have it
-carries 80-95% of the oxygen in the blood
-different isoforms of t that have different ending affinity for oxygen
-isoforms can change depending on age, stage, or phase the fish is in

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43
Q

what is the Bohr effect and when does it become important?

A
  • a shift in the oxygen carrying capacity of hemoglobin
    -present during acidosis to promote unloading
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44
Q

how is the root effect different from the bohr effect?

A

root effect reduced loading/promotes unloading even at high oxygen levels

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45
Q

what are oxygen saturation curves?

A

show how much oxygen is bound in hemoglobin on y-axis and partial pressure on x-axis
-left shift of the curve means unloading Is reduced because affinity for oxygen is increased by hemoglobin
-right shift means unloading is increased, affinity for oxygen decreases

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46
Q

what is p50?

A

assessment of hemoglobin oxygen affinity (half saturation value which is the partial pressure of oxygen at which hemoglobin is 50% saturated with oxygen
-low p50: high affinity for oxygen, good binding, bad unloading
-high p50: low affinity, good unloading, bad uptake
-tells us how much oxygen is needed (lower the p50, the less oxygen needed)

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47
Q

what are the products of metabolism used for in a fish?

A

-cells: nerves, ion transport, etc.
-tissues: heart, locomotion, berating, digestion
-organs: kidney, liver
-behaviours

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48
Q

what is an energy budget?

A

-related to substrates (energy from food and molecules)

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49
Q

what is a metabolic budget?

A

-related to oxygen consumption
-goes to BMR, digestion, and activity

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50
Q

what is a basal metabolic rate?

what does it depend on

A

-oxygen used from just maintaining being alive, unstressed, post digestion
-depends on species, size (oxygen consumption decreases with size), and temperature (increases with temp)

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51
Q

what s specific dynamic action (digestion)?

A

-oxygen consumed from breakdown and transport of molecules due to deamination of a.a.’s in liver and cost of nutrient assimilation (more protein=increased SDA)
-peaks after meals
-fish sometimes stop eating to decrease oxygen consumption when needed

52
Q

what is activity?

A

oxygen consumed from physical exertion
-can be altered by training effects

53
Q

what is VO2 and MO2?

A

-VO2 is volume of oxygen consumed (air breathers)
-MO2 is mass of oxygen consumed (water breathers)

54
Q

what is an aerobic scope?

A

the scope of activity
-max amount the rate of oxygen consumed/uptake can increase to support activities beyond resting
AS=MMR-BMR

55
Q

what is factorial aerobic scope and why is it better than aerobic scope?

A

-difference between max and min oxygen consumption rates
-increases as fish grows usually
-better because is can be used to compare two species

56
Q

what are the two reproductive patterns?

A
  1. iteroparous: high probability of adult surviving after spawning, high variable fry survival, high fecundity, low parental investment
  2. semelparous: low prob of adult surviving after spawning, reliable fry survival, high parental investment, low fecundity
57
Q

what is a reproductive guild?

A

-groups fish based on early dev form, function, and behaviours, preferred spawning grounds, and reproductive behaviours (spawning and incubation)

58
Q

what are the broad categories of reproductive guilds?

A
  1. non-guarders: open sub and broad hiders
  2. guarders: substrate choosers and nest spawners
  3. bearers: internal and external
59
Q

what is vitellogenesis?

A

process of yolk protein formation in oocyte of non-mammalian vertebrates during sexual maturation

60
Q

what occurs during primary growth in oocyte development?

A
  1. one nucleolus: foliculogensis completes, follicle is composed of an oocyte with basophilic ooplasm and spherical germinal vesicle contains a nucleus
  2. multiple nucleolus: 2 or more nucleoli that aren’t located around periphery of germinal vesicle
  3. pernucleolar: nucleoli are located around inner vernal vesicle membrane
  4. oil droplets: oil droplets encompass germinal vesicle
61
Q

what occurs during secondary growth in oocyte development?

A

-appearance of oopmasmic yolk globules
-start of vitologenesis
-characterized by change in oocyte size
-3 phases: early, late and full grown

62
Q

what occurs during oocyte maturation in oocyte development?

A
  1. eccentric germinal vesicle phase: coalescing of yolk globules, germinal vesicle displaced
  2. germinal vesicle migration: GV migrates towards exterior, displaced by yolk
  3. preovulatory: loss of GV, yolk coalesced, oocyte is hydrated to see and ready for ovulation (release into ovary)
63
Q

why is it important to understand oocyte development?

A

-iding vitelogenic oocytes allows you to identify method of spawning
oocyte size distribution can tell you spawning style and fecundity
-counting vitelogenic eggs can tell you spawning style and fecundity

64
Q

what happens during spermatogenesis?

A
  1. spermatogonia: presence of undifferentiated germ cells
  2. spermatocytes: gamete cells which undergo meiosis
  3. spermatids: completed second meiotic division
  4. spermatozoa: presence of spermatozoa within testis
65
Q

what is the speed of goal development affected by?

A
  1. photoperiod: control seasonally of spawning with spawning season
  2. temperature: often dictates changes within spawning season (higher temp decreases spawning season, lower temp increases)
66
Q

What are the properties of water?

A
  1. Melting point: 0°C (high)
  2. Boiling point: 100°C (high)
  3. High specific heat capacity
  4. High surface tension
  5. Solid phase is less dense than liquid phase (ice floats)
  6. Universal solvent – many things are soluble in water
67
Q

What are the four Colligative Properties of water?

A
  1. Adding solutes lowers melting point
  2. Adding solutes increases boiling point
  3. Adding solutes lowers vapor pressure
  4. Adding solutes increase osmotic pressure
68
Q

Why is osmosis important for water breathers?

A
  1. Osmosis allows diffusion of water from high concentration to low concentration; water moves into fish body with its concentration gradient (fish gill acts of semipermeable membrane)
  2. Solutes increase osmotic pressure of a solution; fish body has more solutes in FW less in SW, so water is pushed into gills by osmosis or out
69
Q

What is tonicity?

A

tendency of water to create equal osmotic pressure on either side of a semipermeable membrane

70
Q

What does hypotonic mean?

A

less water so water will move in

71
Q

What does hypertonic?

A

more water to start so water will leave

72
Q

What happens if tonicity isn’t maintained?

A

cells can burst or shrink in size (no longer functional)

73
Q

How are cells of animals are adapted to avoid challenge from the environment?

A
  • Protected by extracellular fluid (ECT)
  • Cells exchange nutrients and waste in their own environment
  • ECF is separated from external environment by epithelial cells
74
Q

What is osmoregulation?

A
  • Regulation of water movement/osmotic pressure
  • The technique for this changes depending on what environment the fish is in
  • Saltwater fish need to drink water constantly
  • Freshwater fish need to excrete water constantly
  • Fish can be osmoregulatory (maintain same blood salinity) or osmoconformer (blood salinity changes with water salinity)
75
Q

What are the different tolerances to salinity?

A
  1. Stenohaline: able to tolerate small changes in salinity
  2. Euryhaline: able to tolerate large changes in salinity
76
Q

what is salinity?

A

mass of solute (salts) in saltwater, related to conductivity of water
* Freshwater: 0.5 ppt or less
* Saltwater: around 35 ppt
* Brackish water: from 0.5-30 ppt

77
Q

what is ionoregulation?

A

regulation of ions in body (closely interrelated with osmoregulation)
all fish do this

78
Q

what organs are involved in water transport?

A
  1. Gills: site of passive gain or loss through osmosis, need to be thin so waterproofing is difficult
  2. Gastrointestinal tract: better control over water retention, not a lot of passive transport (in seawater: site of water absorption (costly), in freshwater: passive gain of water)
    * Small role in FW, huge role in SW
  3. Kidney: urine production, good control of water movement here (SW: fish limit water excreted, FW: excrete lots of water)
    * SW fish suffer from water shortage, low urine production, need to excrete Mg and SO4
79
Q

what organs are involved in ion transport?

A
  1. Gill: fairly good control of ion movement, some passive ion movement, most important site of ion movement
    * mostly monovalent ion transport (Na, K, Cl)
    * Occurs at base of lamellae in specialized cells referred to as chloride cells or mitochondrial rich cells
    * Fish are able to migrate from FW to SW because they can change their gill surfaces to reduce passive ion gains
    Ion transports involved in saline water are:
    i) sodium-potassium pumps for Na, K, ATPase, NKA (costs 20-40% of energy stores)
    ii) sodium hydrogen exchangers and sodium channels for sodium transport
    iii) chloride channels and co-transporters for chloride transport
  2. GIT: fairly good control of ion movement, some passive
    * active movement drives digestion, water uptake, other ion uptake, nutrient uptake
    * not a lot of monovalent ion regulation, lots of divalent (Ca and Mg)
  3. Kidney: good control of ion movement, some limitation
    * hard to passively excrete ions in seawater, retain ions in FW by diluting urine compared to blood
    * FW fish suffer from ion shortage, dilute urine, don’t want to excrete ions
80
Q

what are the Signs of dehydration in SW?

A
  • Difficult to assess in teleost (bony fish)
    a) Can results in anorexia, lethargy, hiding, darkened coloration, reduced or absent defecation, weight loss, enophythalmia (sunken eyes), tachypnea (rapid breathing)
    b) Likely due to kidney not retaining water or GIT not taking up water
81
Q

what are the Signs of water retention in FW?

A

a) May present as edema (swelling) – classified as anasarca and is usually end-stage
b) Anemia
c) Likely due to kidney not retaining ions or gills/GIT not taking up ions

82
Q

what are the symptoms of fish with an ionoregulatory challenge due to gill issues?

A

1) Hypo- hyper-natremia (sodium)
a) Muscle weakness, poor swimming, brain function
2) Hyper- hypo-kalemia (potassium)
a) Arrhythmia, reductions in activity, spasms
3) Hypochloremia (Chloride)
a) Dehydration, diarrhea

83
Q

what are the symptoms of fish with an ionoregulatory challenge due to GIT issues?

A

4) Hypocalcemia (calcium)
a) Muscle spasms, fin or spine damage
5) Hypomagnesemia (magnesium)
a) Arrythmia, blood pressure, bone loss

84
Q

what do blood and tissue pH affect?

A
  • Metabolism, cell volume, cytoskeleton, contraction, cell coupling, intracellular messengers, growth and proliferation, membrane conductance, and membrane flow
85
Q

why is pH always dropping in animals?

A

because we are always producing acid (H+)
continuous proton leak in cells from plasma so capacity to acid-base regulate is critical to maintain pH at a steady state

86
Q

why is pH relevant?

A

it affects enzyme function and protein function

87
Q

production

what are two sources of constant acid loading?

A

1) Net acid production through protein metabolism in animals
2) Metabolic waste product CO2 hydration will produce protons

88
Q

what are the common sources of acidosis?

A

1) Metabolic acidosis: due to mismatch between energy supply and demand because of hypoxemia induced by:
a) Exhaustive exercise (increase in metabolic demand)
b) Environmental hypoxia (limits to uptake or supply of oxygen)
2) Respiratory acidosis: due to elevated environmental CO2 levels resulting in hypercapnia (elevated internal CO2 levels)
*Animals have adaptive mechanisms to avoid problems caused by these events

89
Q

what are the causes of alkalosis?

A

-much more uncommon
* Metabolic: pH of tissue elevated from normal range because of increase in HCO3 molecules
* Respiratory: caused by hyperventilation

90
Q

what are the 4 ways acidosis can be compensated for?

A
  1. buffers
  2. CO2 excretion
  3. increase HCO3 or excrete H
  4. consume H
91
Q

how can buffering compensate for acidosis?

A

Buffer: a molecule that grabs H or OH ions so they don’t contribute to pH changes
a) Intrinsic/closed system buffering:
i) Done by proteins with histidine residues - a.a.’s (good at buffering because they bind to structures with side groups that capture H or OH)
ii) Limited by cell wall, can’t cross it, so H in the cell are bound by these molecules, but not shipped out
b) Extrinsic/open system buffering:
i) Done by CO2 and HCO3
ii) Not limited by cell wall so H can be bound and shipped out of the cell
*Buffering alone can’t return pH to normal, only reduces size of pH change (acidosis)

92
Q

how can increasing CO2 excretion compensate for acidosis?

A
  • CO2 is very lipid soluble and diffuses rapidly from tissues to blood
  • Air breathers can module blood CO2 levels by breathing faster or slower
  • Water breathers can’t, CO2 is lost as quickly as possible, no chance to regulation, breathing rate only affects CO2 loss a little
93
Q

how can excreting H or retaining HCO3 compensate for acidosis?

A

a) Excrete acid:
i) In humans: acid is combined with bicarbonate and excreted as CO2, and some is lots in urine
ii) In fish: H ions can be pumped directly out of gill because water is a solvent, sometimes combined with NH3 and pumped out as NH4
iii) Occurs all the time but can be increased

b) HCO3 uptake:
i) Fish use HCO3 uptake more than acid excretion
* Done at the gills
* Levels of Cl decrease in the blood so that HCO3 can increase (makes it electroneutral)
* Cl is exchanged for HCO3
* HCO3 can’t be accumulated to concentration higher than 30mM because chloride levels can’t drop too low because hypochloremia will occur (lethal)
* So, when CO2 levels become higher, ability to compensate becomes lower

94
Q

how can increasing H consumption by biochemical pathways compensate for acidosis?

A

consume acid by things like ATP synthesis

95
Q

what are the three categories involved in eating?

A

1) Prey capture and transport of food into GIT
2) Digestion, breakdown of food into smaller parts
3) Absorption, transport of the parts into the system

96
Q

Why are eating behaviors involving what the fish eats important to know?

A
  • Impact feeding strategies (catching – hunting, grazing, filter feeding)
  • Feeding mechanism – chewing, scaping, grinding
97
Q

In terms of feeding, how can fish be classified?

A

1) Ecology – where they eat
a) Pelagic: in the water column
b) Benthic: below the water column, ground

2) Preferred food source – what they eat
a) Carnivore: consumes animal products (GIT:body surface – 0.6:1)
b) Herbivore: consumes plant products (2:1)
c) Omnivore: plant and animal (intermediate ratio)
3) Means of capture – how mechanistically they catch food

*all of these and the phylogeny involved largely determine digestive morphology

98
Q

what are the prey nature feeding strategies?

A

1) Hit and run: used by most fast-swimming open water forms
* done by pursuing, engulfing, and swallowing more slowly swimming prey or biting chunks off on the way by
* need good biting or grasping jaw apparatus
Requirements:
a) firm jaw construction
b) placement as well as large, powerful muscles to shut jaws

2) Filter feeding: strain or filter out small planktonic organisms
Requirements:
a) Ability to hold mouth wide open for long periods
b) Modified gill rakers for collecting particles and moving them to GIT

3) Gape and suck: majority of fish feed this way, passive way of feeding
* Done by opening the mouth, simultaneously lowering floor of mouth, expanding sides of cavity
* Induces sudden increase in volume and creates negative pressure that results in a sudden rush of water into the mouth that brings the prey in

99
Q

what are the primary functions of the digestive tract?

A

1) Digestion: mechanical and chemical breakdown
2) Absorption: passive diffusion and active transport, salt/water balance, nutrient absorption
3) Excretion: elimination of waste products

100
Q

food—down into smaller bits

what processes are involved in digestion?

A

1) Mechanical reduction of particle size (easier to absorb)
2) Solubilization of organics (by enzymes) and inorganics (by pH)
3) Emulsification of fats (breakdown into tiny droplets to digest)

101
Q

what is absorption?

A

the process that allows ions and molecules to pass through membranes of the intestinal tract into the blood, lymph, hemolymph, etc., to be metabolized by the animal
* Proteins absorbed as amino acids
* Fats absorbed as fatty acid complexes (micelles)
* Carbohydrates absorbed as monosaccharides or simple sugars

102
Q

what is the mouth in the GIT tract for? examples?

A

1) Mouth: oral valve that controls water movement, houses dentation
* Ex: channel catfish: large mouth, capture prey (predaceous), no teeth
* Ex: common carp: small mouth, bottom feeder, pharyngeal teeth, grinds food (plants)
* Ex: tilapia: combination, plankton feeder, gill rakers, brood protection in mouth

103
Q

what is the pharynx in the GIT tract for?

A

houses gills, gill rakers (important for filter feeders), pharyngeal slits, pharyngeal teeth (gill modification that helps with mechanical breakdown)

104
Q

what is the esophagus in the GIT tract for? examples?

A

separated from stomach by sphincter, short, equipped with longitudinal and circular muscles for swallowing (peristaltic movement), taste buds
* May have role in osmoregulation
* In physostomous fish: site of connection to swim bladder (pneumatic duct), controlled by nervous system which manipulates the content of the swim bladder

105
Q

what is the stomach in the GIT tract for? examples?

A

uses acid digestion, or pepsin (carnivores), absent in some fish, enzymes present are tailored toward diet of the fish
Two groups:
a) Without stomach (ex. Carps)
b) With stomach (ex. Cold-water – salmonids, warm-water – tilapia, catfish, eels, groupers)
* Ex: Channel catfish: true stomach with HCl and pepsinogen in presence of food
* Ex. Common carp: no stomach, bulb instead, relies on constant low pH, no digestive enz.
* Ex. Tilapia: modified stomach (pocket), secretes HCl, pH varies with digestinal flow

106
Q

how does digestion occur in a true stomach?

A
  • Food enters through esophagus
  • Neural and hormonal processes stimulate digestive secretions
  • Stomach distends due to food, parietal cells in lining secrete gastrin assisting in digesting
  • Gastrin and acids convert pepsinogen to pepsin (proteolytic enzyme that lyses protein into small peptides for easier absorption)
  • Movement of digesta out of stomach is controlled by pyloric sphincter (chyme: mix of digesta, gastric juices, and mucus)
  • Only proteins are digested in the stomach
107
Q

what is the intestine in the GIT tract for? what are the two parts?

A

separated from the stomach by a sphincter, enzymes present are tailored to diet, includes a midgut and a hindgut
Responsible for:
a) Enzymatic digestion by:
i) Amylase: carbohydrate breakdown
ii) Proteases: protein breakdown
iii) Lipases: lipid breakdown
iv) Cellulase: cellulose breakdown
b) Absorption of nutrients into intestinal wall
Midgut: mildly alkaline and contains enzymes from pancreas/intestinal wall and bile from liver, most absorption happens here, essential for food breakdown and absorption
Hindgut: fine tuning – absorbing required elements that may have been missed in the midgut

108
Q

how do the intestine (midgut and hindgut) lengths vary depending on type of diet and species? examples?

A
  • Carnivores: 0.2-2.5 times body length
  • Omnivores: 0.6-8.0 times body length
  • Herbivores: 0.8-15.0 times body length
    *the more plant material consumed, the longer the intestine in most cases, also related to nutrient amount available in the food (more nutrients in food, shorter intestine – takes less time to digest)
    *midguts have the most absorption occurring compared to stomach and hindgut
  • Ex. Channel catfist: length less than whole body, slightly basic, many folds (high SA)
  • Ex. Common carp: digestive tract is 3x body length, similar absorption to catfish
  • Ex. Tilapia: tract is 6-8x body length, absorption similar to other sp.
109
Q

what are the way absorption can occur?

A

1) Passive diffusion: concentration gradient
2) Facilitated diffusion: manipulated concentration gradients
3) Active transport: ATP required
4) Pinocytosis: particles engulfed

110
Q

what are the three ways proteins cn be absorbed?

A

1) PEPT (SLC15A): transports amino acids, linked to Na/H exchange (Na in, H out, H symporter brings amino acids in), energy required
2) Na linked co-transport: ATP needed
3) Transcytosis/pinocytosis: required energy to go against conc. gradient, used for small peptide chains in large intestine
*then molecules are moved into the blood by basolateral transport (could be Na or H amino acid exchange or exocytosis)

111
Q

how are lipids absorbed?

A
  • Bile salts coat fat droplets (creates micelles where lipases can work inside)
  • Lipases breakdown fats into fatty acids within micelles
  • Fatty acids and monoglycerides leave the micelle and enter the blood by diffusion
  • Not energetically costly
112
Q

how are carbohydrates absorbed?

A
  • Involves two common cell transmembrane transporters: SGLT (SLC5A) – Na/sugar co-transporter that uses ATP (gets sugar into intestinal mucosa from lumen of intestine) and GLUT (SLC2A) – channels for facilitated diffusion, needs ATP indirectly (gets sugars from intestinal mucosa to capillary)
113
Q

what is hindgut fermentation?

A
  • Some fish have a modified hindgut that has fermentation sacs populated by bacteria that ferment and breakdown indigestible plant material
114
Q

what is a spiral valve used for?

A
  • Found in Chondrichthyes (all), Sarcopterygians (most), and primitive Actinopterygii (some)
  • Increases the surface area without increasing intestinal length or size
  • Allows for increased absorption with less weight-volume
115
Q

what are the organs associated with digestion and what do they do?

A
  • Liver produces bile (unless they have a gall bladder)
  • Pancreas produces digestive enzymes (primary source)
116
Q

what are the important questions to ask when deciding stocking density?

A

1) What oxygen levels are needed?
* Tilapia don’t need much, salmonids need much more
2) What is the expected ammonia buildup?
* Net pens have high flow, less build up, RAS need to remove build up
3) How metabolically active are the fish?
* Tuna: high, halibut (benthic): low
4) What behaviours are seen with crowding?
* Tilapia: stunted, sturgeon: runts, artic char: little effect
5) How much does your system change daily/annually?
* Temperature, light, biological growth, inflow, life cycle
6) How often do you need to assess?
* How fast do the fish grow?

117
Q

what is Kleibers law?

A
  • As fish grow, metabolic demands increase but the metabolic demand per kilo of mass decreases
  • Estimating the oxygen consumption of a small fish based on a large fish will kill the fish
  • Feed requirements are similar
  • Need equations to estimate the difference depending on size
118
Q

why is fish growth hard to predict?

A

its not linear, hard to plan for
past experience is very useful

119
Q

how can you predict fish weight without weighing the fish?

A
  • Fish show a relationship between length and weight which is species dependent but is usually around exponential value of 3
  • Length can be used to determine weight
120
Q

what is stocking density?

A

density at which fish are put into tanks

121
Q

what is rearing density?

A

maximum density the fish should be allowed to get in a tank

122
Q

what is loading density?

A

level of water inflow needed per kg fish to support oxygen consumption rates and ammonia clearance

123
Q

what is the purpose for knowing max fish density?

A
  • Know when to act to reduce density (split or harvest)
  • Can calculate greatest water needs (inflow, chemicals, oxygen levels)
  • Can plan for harvest (assuming we know growth rates or FCR)
  • can calculate initial stocking densities (loading)
124
Q

what is the problem with SGR and RGR and what is the solution?

A

-can over or under estimate size of fish
-solution: von bertalanffy growth functions, incorporates changes in growth rates over time into calculations

125
Q

what has an effect of SGR and RGR?

A

1) age: decreases as fish age
2) temperature: growth has an optimal temperature range
a) thermal growth coefficient: a constant that estimates the effect of temperature on growth, can be applied to growth prediction formulas
3) feed: changing protein content by a small amount can greatly increase or decrease growth
4) density: knowing ideal density can allow you to optimize holding
a) extensive systems: associated with food availability
b) semi-intensive: food costs, water quality
c) intensive: water quality, behaviour, stress

126
Q

what is feed conversion ratio (FCR)? why is it useful?

A
  • looks at relationship between feed in and mass out (feed in (kg)/fish out (kg)) - unitless
  • useful because it you can optimize growth
  • changes with age
  • can be used to estimate SGR and RGR

Fish Behaviour (1 decks)

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