Fish Health Management Lab 1: Water Quality January 25 th, 2010 David Burbank

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 (NH 3 ) –Nitrite (NO 2 - ) –Nitrate (NO 3 - ) 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 (NH 4 + ) un-ionized (NH 3 ) –nitrite (NO 2 - ) –nitrate (NO 3 - )

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

Ammonia Ammonia (NH 3 ) results from the breakdown of fish feed, and waste Two forms: –ionized (NH 4 + ) –un­ionized (NH 3 ) Un­ionized ammonia concentration is a function of pH and temperature Chronic exposure (un­ionized form) –0.06 mg/L is toxic to warm water fish –0.03 mg/L is toxic to salmonids

Nitrite Nitrite (NO 2 - ) 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 un­ionized 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 (NO 3 - ) is the final breakdown product in the oxidation of ammonia Nitrate is relatively non­toxic 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 (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 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 –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 ppm TSS reasonable for salmonids

Chlorine Chlorine, (sodium hypochlorite or calcium hypochlorite) reacts with water to form strong acid Cl 2 + H 2 0 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) 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 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