fish health management lab 1: water quality january 25 th, 2010 david burbank...
Post on 19-Dec-2015
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TRANSCRIPT
Aquatic Environment
• Water quality is one of the most important factors to maintain fish health.
• Poor water quality causes more losses in aquaculture than any other problem.
• Factors that influence water quality/quantity in aquaculture:– Feed rates– Feed types– Flow rates– Tanks/containers (flow dynamics)– Temperature
Water quality testing
• Daily or weekly tests– Basic tests– Relatively quick and inexpensive – i.e. Temp, DO, Cl, ect…
• Semi-annual or annual– Extensive & more precise– Expensive and time consuming– i.e. Heavy metals
• Are catered to specific
concerns for the facility
Daily or Weekly
• Dissolved oxygen• Temperature• Nitrogen compounds
– Ammonia (NH3)
– Nitrite (NO2-)
– Nitrate (NO3-)
• pH• Alkalinity
• Carbon Dioxide• Hardness• Hydrogen sulfide• Total suspended
solids• Chlorine
Dissolved Oxygen
• Inadequate DO can cause mortality and contribute to chronic stress and ill health
• Solubility– dependent on:
• Temperature
• Elevation
• Salinity
• Safe levels– greater than 5 mg/L for salmonids– greater than 3 mg/L for warm water fish
Mg/L
Dissolved Oxygen
• Uptake influenced by condition of gills– Partial pressures are important– If lamellae are not healthy, the demand may
not be met.
• Water DO levels below saturation can adequately provide saturation of hemoglobin, however a safety margin should be maintained.
Oxygen Requirements
• Dependent on Temperature– Metabolic increases with temperature
• Dependent on demands of organism– Energetic demands: swimming, digestion, etc.– Energetic costs of ventilation– Efficiency of uptake varies in species
Temperature
• Effects– metabolic rate doubles for
every 8C increase– Influences spawning– Influences growth– Influences pathogens
• Fish Categories– warmwater– coolwater– coldwater
Nitrogen Compounds
• Types– dissolved gas– ammonia
• ionized (NH4+)
• un-ionized (NH3)
– nitrite (NO2-)
– nitrate (NO3-)
Nitrification
NONO33-- NHNH33
1½ O1½ O22
nitrosomonas nitrosomonas nitrobacter nitrobacter
1½ O1½ O22 NONO22
--
• Requires 3 moles oxygen to convert one mole of ammonia to nitrate
• Nitrification is an acidifying reaction
Ammonia
• Ammonia (NH3) results from the breakdown of fish feed, and waste
• Two forms:– ionized (NH4
+)
– un ionized (NH3)
• Un ionized ammonia concentration is a function of pH and temperature
• Chronic exposure (un ionized form)– 0.06 mg/L is toxic to warm water fish
– 0.03 mg/L is toxic to salmonids
Nitrite• Nitrite (NO2
-) is the intermediate product in the breakdown of ammonia to nitrate (nitrification)
• Nitrite levels greater than 0.5 to 0.6 mg/L or 10 times higher than the toxic threshold for un ionized ammonia are toxic to fish
• Catfish will tolerate 13 mg/L• Salmonids will tolerate <0.3 mg/L• Decreasing pH increases toxicity
Nitrite• Brown blood disease (Methemoglobinemia)
– Iron in the heme molecule is reduced and cannot transport oxygen
– Blood appears dark in color and fish cannot meet oxygen demands
• Treatment – Salt– Chloride ions out-compete nitrite– Recommend 10:1 ratio
• Hypertrophy and hyperplasia in the gill lamellae• Lesions/hemorrhaging in thymus
Nitrate
• Nitrate (NO3-) is the final breakdown product
in the oxidation of ammonia
• Nitrate is relatively non toxic to fish at concentrations up to 3.0 mg/L
• May be problem in embryo development
Nitrogen thresholds for salmonids
pH
• Measure of the hydrogen ion concentration
• 1-14 scale– less than 7 acidic– greater than 7 basic
• Safe range– generally 6.5-9.0
(species variable)
Carbon Dioxide
• Sources– bi-product of respiration of fish
and phytoplankton– wells
• carboniferous rock (i.e. black shale, coal)
• Removal– intense aeration– buffers
• calcium carbonate• sodium bicarbonate
CH2O (food) + O2 CO2 + H2O
Alkalinity• Alkalinity is the capacity of water to buffer
against wide pH swings• Acceptable range 20-300 mg/L
CaCO3 + CO2 + H2O Ca+2 + 2HCO3-
Bicarbonate: CO2 + H2O H+ + HCO3-
Carbonate: HCO3- H+ + CO3
-
Effects of calcite lime:
*Dolomite CaMg(CO3)2 yields 4HCO3-
Hardness• Hardness is the measure of divalent cations
– Calcium– Magnesium– Suggest > 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– If hardness is deficient then fish grow poorly
Hydrogen Sulfide
• Source– Well water– Ponds
• shift from aerobic to anaerobic breakdown of wastes
– Can develop under net pens
• Extremely toxic to fish• Removal
– Intense aeration– Draining and drying of pond
Total Solids
• Types– suspended– settleable
• Sources– runoff– uneaten food– feces
• Safe levels– less than 1,000 mg/L
• Removal– filtration– settling chambers
Suspended Solids
• Potential problems– Source of irritation/nutrients on gills– Inflammation and damage to gills– Bacterial or fungal colonization on gill surface
• Reduce oxygen transport
• 80 - 100 ppm TSS reasonable for salmonids
Chlorine
• Chlorine, (sodium hypochlorite or calcium hypochlorite) reacts with water to form strong acid
• Cl2 + H20 H0Cl H+ + Cl -
Chlorine
• Disinfectant– municipal water– cleaning tanks and equipment
• Safe levels– less than 0.03 mg/L
• Removal– intense aeration– sodium thiosulfate
• 1 mg/L for every mg/L chlorine– Sunlight– Filtration (carbon filters)
Chlorine toxicity
• Acid is more toxic than hypochlorite ion
• Destroys epidermal surfaces (especially 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
Heavy Metal Contaminants
• Heavy metals - Cd, Cu, Zn, Hg, must be all < .1 mg/L.
• In aquaculture watch out for plumbing systems (copper, zinc alloys) PVC is preferred choice.
• Soft water makes a difference in toxicity of metals
Dissolved Gasses
• Problem gasses– nitrogen
• maintain less than 110%
• Problem sources – wells and springs– leaky pipes– Dams
leaky pipeleaky pipe
Popeye/exophthalmiaPopeye/exophthalmia
dorsal viewdorsal view
Characteristics of gas bubble disease
• Bubbles under skin
• fins
• tail
• mouth
• gas emboli in vascular system = death
• similar to bends or decompression sickness