Aquatic Environment

1
Aquatic Environment

• Water quality and quantity is one of the most
  important factors to maintain fish health.
• Inadequate water quality causes more losses than
  any other problem!
• Factors that influence water quality/quantity
• Feed rates
• Feed types
• Flow rates
• Tanks/containers (flow dynamics)
• Temperature

2
Water Quality

• Daily or weekly tests

• Semi-annually or annually

3
Daily or Weekly

• Dissolved oxygen
• Nitrogen compounds
• ammonia
• nitrite
• nitrates
• pH
• Alkalinity
• Hardness

• Carbon Dioxide
• Temperature
• Hydrogen sulfide
• Total suspended solids
• Chlorine

4
Dissolved Oxygen

• Importance
• highest cause of mortality
• Solubility
• variables
• Safe levels

5
Dissolved Oxygen

• Uptake influenced by condition of gills

6
Oxygen Requirements

• Dependent on temperature
• Dependent on demands of organism

7
Nitrogen Compounds

• Types
• dissolved gas
• ammonia
• ionized
• un-ionized
• nitrite
• nitrate

8
Ammonia

• Ammonia
• Two forms
• Chronic exposure (un-ionized form)

9
Nitrite

• Nitrite (NO2-)
• Nitrite levels greater than 0.5 to 0.6 mg/L or 10
  times higher than the toxic threshold for
  unionized ammonia is toxic to fish
• Decreasing pH

10
Nitrite

• Brown blood disease (Methemoglobinemia)
• Blood appears dark in color
• Treatment
• Recommend 101 ratio
• Hypertrophy and hyperplasia in the gill lamellae
• Lesions/hemorrhaging in thymus

11
Nitrate

• Nitrate (NO3-) is the final breakdown product in
  the oxidation of ammonia

12
Nitrification

• Requires 3 moles oxygen to convert one mole of
  ammonia to nitrate
• Nitrification is an acidifying reaction

13
Relationships
14
pH

• Measure of the hydrogen ion concentration
• 1-14 scale
• less than 7 acidic
• greater than 7 basic
• Safe range
• 6.5-9

15
Carbon Dioxide
CH2O (food) O2 ? CO2 H2O

• Sources
• Wells
• carboniferous rock
• Removal
• buffers
• calcium carbonate
• sodium bicarbonate

16
Alkalinity

• Alkalinity is the capacity of water to buffer
  against wide pH swings
• Acceptable range 20-300 mg/L

Bicarbonate CO2 H2O ? H HCO3-
Carbonate HCO3- ? H CO3-
Effects of calcite lime
CaCO3 CO2 H2O ? Ca2 2HCO3-
Dolomite CaMg(CO3)2 yields 4HCO3-
17
Hardness

• Hardness is the measure of divalent cations
• Suggest gt 50 ppm
• Hardness is used as an indicator of alkalinity
  but hardness is not a measure of alkalinity
• Magnesium or calcium sulfate increases hardness
  but has no affect on alkalinity

18
Hydrogen Sulfide

• Source
• Well water
• Ponds
• Under net-pens
• Extremely toxic to fish
• Removal

19
Total Solids

• Types
• suspended
• settleable
• Sources
• runoff
• uneaten food
• feces

• Safe levels
• less than 1,000 mg/L
• Removal
• filtration
• settling chambers

20
Suspended Solids

• Potential problems
• Reduce oxygen transport
• 80 - 100 ppm TSS reasonable for salmonids

21
Chlorine

• Disinfectant
• Safe levels
• less than 0.03 mg/L
• Removal
• Sunlight
• Chlorine reacts with water to form strong acid

22
Chlorine toxicity

• Acid is more toxic than hypochlorite ion
• Destroys epidermal surfaces gills
• Toxicity depends on temp, DO, free chlorine
  present, presence other pollutants
• Residual chlorine (free plus chloramine)0.2 -
  0.3 ppm kills fish rapidly
• chlorine and nitrogenous organics chloramines
  that are very toxic

23
Temperature

• Effects
• Fish Categories
• warmwater
• coolwater
• coldwater

24
Heavy Metal Contaminants

• Water quality is important
• Heavy metals - Cd, Cu, Zn, Hg, must be all lt .1
  mg/L.
• In aquaculture watch out for plumbing systems
  (copper, zinc alloys)
• Soft water makes a difference in toxicity of
  metals

25
Dissolved Gasses

• Problem gasses
• maintain less than 110
• Problem sources
• leaky pipes

26
Characteristics of gas bubble disease

• Bubbles under skin
• fins
• tail
• mouth
• gas emboli in vascular system death
• similar to bends or decompression sickness

27
Spill vs no spill management of Columbia River

• History - Excess water removed used to be a big
  problem.
• Rough guidelines for negative responseClean
  water act says 110 is standardwhat difference
  between 110 and 120?
• Effects on salmonids
• 103 104 yolk sac and fingerlings
• 105- 113 older fingerlings and yearlings
• 118 adults

28
Columbia River

• In 1960s in Columbia River,
• Adults
• Exophthalmia
• bubbles in skin and mouth
• hemorrhaged eyes later cause blindness - impair
  spawning
• External symptoms disappear rapidly after death
• Changed water use and flip lips
• 1990s high spill head burns in salmon

29
Does Compensation Occur

• One meter depth about 10 reduction in gas
  saturation.
• Late 1970s fish were deeper than 1.5 m in 110
  saturation
• Fish were using shallower water in normal
  saturation
• Fish ladders require fish to come to surface or
  near surface

30
Questions/uncertainty

• Behavioral Compensation? Does it occur?
• Migration pathways for Adult salmon
• Migration pathways for juvenile salmon
• How good are flip lips?
• Voluntary vs non-voluntary spill issues?
• Immediate vs delayed mortality?
• Predisposition to other invasions?