Fish Health ManagementLab 1: Water Quality

January 25th, 2010

David Burbankburb2155@vandals.uidaho.edu

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