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

Water Quality

• Daily or weekly tests • Semi-annually or annually

Daily or Weekly

• Dissolved oxygen• Nitrogen compounds

– ammonia

– nitrite

– nitrates

• pH• Alkalinity• Hardness

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

Dissolved Oxygen

• Importance– highest cause of mortality

• Solubility– variables

•

• Safe levels

Dissolved Oxygen

• Uptake influenced by condition of gills– –

•

Oxygen Requirements

• Dependent on temperature

• Dependent on demands of organism

– – – –

Nitrogen Compounds

• Types– dissolved gas

– ammonia• ionized

• un-ionized

– nitrite

– nitrate

Ammonia• Ammonia

–

• Two forms –

–

• • Chronic exposure (un-ionized form)

Nitrite• Nitrite (NO2

-) –

• Nitrite levels greater than 0.5 to 0.6 mg/L or 10 times higher than the toxic threshold for un ionized ammonia is toxic to fish

• • Decreasing pH

–

Nitrite• Brown blood disease (Methemoglobinemia)

–

– Blood appears dark in color •

• Treatment – – – 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

•

•

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

Relationships

pH

• Measure of the hydrogen ion concentration

• 1-14 scale– less than 7 acidic

– greater than 7 basic

• Safe range– 6.5-9

Carbon Dioxide

• Sources–

– Wells• carboniferous rock

• Removal–

– buffers• calcium carbonate

• sodium bicarbonate

CHCH22O (food) + OO (food) + O22 COCO22 + H + H22OO

Alkalinity• Alkalinity is the capacity of water to buffer against

wide pH swings• Acceptable range 20-300 mg/L

CaCOCaCO33 + CO + CO22 + H + H22O O Ca Ca+2+2 + 2HCO + 2HCO33--

Bicarbonate:Bicarbonate: CO CO22 + H + H22O O H H++ + HCO + HCO33--

Carbonate:Carbonate: HCO HCO33-- H H++ + CO + CO33

--

Effects of calcite lime:Effects of calcite lime:

*Dolomite CaMg(CO*Dolomite CaMg(CO33))2 2 yields 4HCOyields 4HCO33--

Hardness• Hardness is the measure of divalent cations

–

–

– 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

–

Hydrogen Sulfide

• Source– Well water

– Ponds •

– Under net-pens

• Extremely toxic to fish• Removal

–

–

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– – –

• Reduce oxygen transport

• 80 - 100 ppm TSS reasonable for salmonids

Chlorine• Disinfectant

– –

• Safe levels– less than 0.03 mg/L

• Removal– –

• – Sunlight

• Chlorine reacts with water to form strong acid

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

Temperature

• Effects–

–

–

–

• Fish Categories– warmwater

– coolwater

– coldwater

Heavy Metal Contaminants

• Water quality is important• Heavy metals - Cd, Cu, Zn, Hg, must be all < .1

mg/L.• In aquaculture watch out for plumbing systems

(copper, zinc alloys) –

• Soft water makes a difference in toxicity of metals –

Dissolved Gasses

• Problem gasses–

• maintain less than 110%

• Problem sources –

– leaky pipes

– 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

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

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

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

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?