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 testsSemi-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 – Two forms – Chronic exposure (un-ionized form)

Nitrite Nitrite (NO 2 - ) – 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 (NO 3 - ) is the final breakdown product in the oxidation of ammonia

Nitrification NO 3 - NH 3 1½ O 2 nitrosomonasnitrobacter NO 2 - 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 CH 2 O (food) + O 2  CO 2 + H 2 O

Alkalinity Alkalinity is the capacity of water to buffer against wide pH swings Acceptable range mg/L CaCO 3 + CO 2 + H 2 O  Ca HCO 3 - Bicarbonate: CO 2 + H 2 O  H + + HCO 3 - Carbonate: HCO 3 -  H + + CO 3 - Effects of calcite lime: *Dolomite CaMg(CO 3 ) 2 yields 4HCO 3 -

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 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) 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 pipe Popeye/exophthalmia dorsal 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 response Clean water act says 110% is standard what difference between 110 and 120%? Effects on salmonids –103 – 104% = yolk sac and fingerlings – % = 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?