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Vet-105 Animal husbandry > Week 10 Fish Husbandry > Flashcards

Week 10 Fish Husbandry Flashcards

1
Q

Fish are ectothermic - what does that mean ?

A

Cold blooded so body temperature is dependant on their surroundings

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2
Q

What protection from diseases and water chemistry do fish have ?

(3)

A
  1. Mucus layer
  2. Skin
  3. Immune system
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3
Q

What are disease causing pathogens in fish?

(4)

A
  1. Bacteria e.g. Fin-rot
  2. Fungi
  3. Parasites e.g. white spot
  4. Viruses e.g. Koi herpes virus (KHV), Spring viraemia of carp (SVC)
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4
Q

Name the diseases in fish

A
  1. Fin rot
  2. Fungus
  3. White spots
  4. Koi Herpes Virus
  5. Spring Viraemia of Carp
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5
Q

What is the cause of most health issues in fish?

A

Poor husbandry → poor environmental conditions for fish →
increased stress and lowered immune system → prone to diseases

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6
Q

What fish require from their environment?

(4)

A
  1. Good water quality
  2. Oxygen
  3. Stable conditions
  4. Complete and balanced diet
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7
Q

What are the 4 tank and water system types

A
  1. Marine (eg estuaries, ocean) or freshwater (lakes and rivers) – vary in salinity
  2. Tropical or temperate – vary in temperature
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8
Q

What factors must be monitored in water quality?

7

A
  1. Dissolved gases
  2. Nitrogenous compounds
  3. Temperature
  4. pH
  5. Hardness
  6. Alkalinity
  7. Salinity
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9
Q

Why must fish be very efficient at extracting oxygen from
water?

A

Water only holds 3% of the oxygen cf with air of the same volume

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10
Q

What is Hypoxia?

A

low oxygen levels

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11
Q

What causes hypoxia?

A
  1. High stocking density
  2. Overfeeding
  3. Many rotting organic matter being broken down by bacteria
  4. Excessive plants
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12
Q

How much dissolved oxygen is needed?

A

**Most fish require at least 6mg/l DO
**
- Vary with species, age, size and health of the fish
- Stress & feeding increase oxygen requirements in fish

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13
Q

How dissolved oxygen (DO) is measured?

A
  1. Photometer
  2. Electronic meter
  3. Chemical test kit
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14
Q

What happens if DO levels become too low ?

A
  • Fish gasp and die
  • Larger fish succumb first
  • Orfe species are the first to die
  • Fish look spotless/perfect = characteristic of death due to low DO
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15
Q

Cuases for low DO?

A
  • High temperatures in summer
  • higher demand for oxygen but warm water holds less oxygen
  • During the night
    • Pond plants use up oxygen
    • Nights are muggy and warm making DO even lower
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16
Q

Describe extensive fish keeping

A

E.g. rivers
* Large area, low stocking density
* Low risk, low return
* Low risk of stress to fish

17
Q

Describe intensive fish keeping

A

e.g. tanks, ponds, aquaria
* High stocking density
* High risk, high return - Need to input a lot of energy, food and
investment for it to work
* High risk of stress to fish
* High stocking density will decrease DO

18
Q

What are other dissolved gases?

A
  • Carbon dioxide - Produced by fish, bacteria and plants at night
  • Nitrogen - Issue when nitrogen forced into water at high pressure and faster rate that it can diffuse out
    - can cause air emboli in fish
19
Q

Nitrogenous compounds

A
  • Fish excrete ammonia (NH3) from gills & kidneys as a waste product
  • Bacteria (e.g. Nitrosomonas) found in water & the filter convert NH3 to nitrite (NO2) by oxidation
  • Other bacteria (e.g. Nitrobacter) then oxidise nitrite to nitrate (NO3)
    Ammonia (NH3) → Nitrite (NO2) → Nitrate (NO3)
20
Q

What can fish tolerate more nitrate, nitrite or ammonia?

A

Nitrate more than ammonia and nitrite

Ammonia & nitrite are both v. toxic to fish

Maximum nitrate: 50 mg/l
Maximum ammonia level: 0 mg/l
Maximum nitrite level: 0 mg/l

21
Q

Describe the nitrogen cycle

A
  1. Fish faeces, uneaten food
    and dead plants produce
    ammonia
  2. Nitrification: Ammonia
    converted/oxidised to
    nitrites and then nitrates
    by bacteria
  3. Nitrates are then
    absorbed by plants, are
    denitrified to nitrogen gas
    or removed from the
    water system with water
    changes
22
Q

How do bio filters work?

A
  • Use naturally occurring bacteria to breakdown ammonia into nitrites and then nitrates (less toxic)
  • Takes several weeks for these bacteria to grow in filters and function efficiently
23
Q

What are the most common causes of ammonia/nitrite problem?

3

A
  1. Too many fish added to pond/tank too quickly or too many fish in a mature pond
  2. Immature filter – can take 3 months to fully mature (New Pond Syndrome (NPS))
  3. Overfeeding
24
Q

How to measure nitrogenous compounds?

A
  1. Chemical test kit
  2. Ion-specific photometer
25
Q

Why is temperature control important for fish?

A
  1. Fish are ectothermic
  2. Metabolic, feeding and growth ratesof fish depend on it
  3. Sudden changes in temp = stress so more prone to disease
  4. Higher temp = less DO + more ammonia
26
Q

Describe fish in winter

A

In winter fish are inactive (<10°C) and resume activity and growth
in summer

27
Q

Describe fish in Autumn

A

Fish ‘slow down’, their immune system so become suppressed therefore opportunistic pathogens (fin-rot, fungus) may cause infection

28
Q

Describe the issue with transition from winter to spring

A
  • As water starts to warm after winter, opportunistic pathogens increase quicker than the fish’s immune system (Spring Mortality Syndrome)
  • Spring is a classic period for attack by viruses (Spring Viraemia of
    Carp (SVC), Koi Herpes Virus (KHV)) with v. high mortality (95%)
29
Q

Describe relation betwen temp and water density

A
  • Water density changes with temperature
    → Highest density at 4oC
    At ↑ temp: warm water floats above cold water
    At ↓ temp < 4oC: cold water at the top and turns to ice → ponds outdoors need to be at least 1m deep so fish can survive in warm water underneath the ice
30
Q

Why is water pH important for fish?

A
  • Change of <1 unit in pH can be fatal for fish
  • If will acclimatise fish then change pH a max of 0.3 units per day
  • Most species kept by hobbyists are at pH range 6–8
31
Q

Examples of underlying causes for low pH

A
  1. Use of tap water which has chlorine
  2. . Runoff from peaty soil into pond in heavy rain
32
Q

Examples of underlying causes for high pH

A
  1. Runoff from limed soil/concrete into pond in heavy rain
  2. Build-up of ammonia
33
Q

How to measure pH

A

Indicator test strips
Chemical test kit
Electronic meter

34
Q

What is water hardness?

A

Amount of dissolved calcium and magnesium in water
→ important as affects the ability of fish to osmoregulate & control fluid balance

35
Q

How is pH linked to water hardness?

A

Soft water usually acidic and hard water is more alkaline

36
Q

How is water harness measured?

A

Chemical test kit
Colorimetric photometer

Vet-105 Animal husbandry (4 decks)

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