Fish & Invertebrate Husbandry, WQ, & Enrichment Flashcards
1
Q
What are the four types of culture systems?
Describe the components of aquaria.
What are some of the challenges of managing ponds?
Describe the effect of temperature, pH, and alkalinity on the dissolved oxygen and CO2 in a pond - as well as their effects on the toxicity of ammonia and copper.
What are flow through culture systems used for?
What are semi-opoen culture systems used for?
A
Four major types of culture systems: aquaria, pongs, cages, and raceways with the major difference between them being how quickly the water turns over.
- Flow through systems (raceways) constantly add new well oxygenated water to dilute out toxins.
- Aquaria can hold higher fish densities because of supplemental life support systems.
Closed culture systems: Aquaria
- Composed of the aquarium, substrate (crushed coral reacts with acids in the tank to release calcium and magnesium to increase hardness), filters (corner, under gravel, outside, and canister – circulate water for oxygenation (mechanical) and remove nitrogenous waste products via bacteria that colonize the filter bed (biological) and remove particulates/pigments (chemical)), aerator, other purification (foam fractionation), live plants, decorations, heater, disinfection unit (used to remove pathogens from the water – ozone or UV)
Closed culture systems: Ponds
- It is not possible to treat the pond without affected the fish, and not possible to treat the fish without affecting the pond ecosystem.
- Fertilization (used to stimulate growth of algae to produce oxygen and remove ammonia), aerator, liming (neutralize acids to maintain pH – also provides carbonate, calcium and magnesium)
- Commercial ponds face problems similar to intensive animal agriculture. High stocking density mandates high nutrient input from feed which causes a buildup of toxic wastes. Large fluctuations in oxygen. Disease can spread rapidly – herd health approach
- Farm pond – raise fish (channel catfish and gamefish). Source of food an enjoyment for owner. Medical advice should be incorporated into routine calls made for care of other farm animals. May be deep, leading to stratification problems.
- Pet fish ponds – goldfish and koi. Supplementary life support needed if fish are in a high density.
Flow through culture systems
- Also known as open systems are primarily used to raise salmonids.
- High water turnover rate and flushing effect to maintain water quality. Continually flowing water enters at one point and exits another. Major limitation is amount of water available for use.
- Most common type is the raceway – long narrow ditch longitudinal divided in to compartments with a waterfall between each one. Oxygen is the major limiting factor to the number of fish possible.
- Some farms use liquid oxygen 🡪 can lead to ammonia toxicity and low pH. Not feasible to control water quality variables in these systems.
- Regulations restrict the type and amount of effluents released. Many systems use surface (stream water) which depends on rainfall and thus can case overcrowding and high temperatures in the summer or during droughts. Ground water is usually free of pathogens, not chemically influenced by rainfall and chemically stable.
Semi-open culture systems
- Cages (net pens) intermediate between open and closed. There are floating, fixed, submerged, and submersible. Fixed cages have net bag driven into the bottom, floating cages have a buoyant collar that supports the net, submerged cages remain permanently below the water while submersible cages can move vertically in the water to take advantage of environmental conditions.
- Tilapia, carp, salmonids, sea bass, and sea beam
2
Q
Describe the mechanics of water conditioning.
What are the typical systems used with marine mammals? How does that differ with fish?
How does mechanical filtration work? What about flocculation?
How does foam fractionation work?
How does biological filtration work? What considerations should be given to biofilter design?
How does ecological filtration work?
What sterilizing agents and disinfectants can be used? Which should not be used?
Where should heat exchangers be placed in the filtration process?
A
Fowler 7 Ch 24 - The Mechanics of Aquarium Water Conditioning
- Open- direct circulation with natural body of water and do not usually require filtration
- Semiclosed- basic filtration systems but rely on partial exchanges with external water body
- Closed- most complex, includes all types of filtration
- Simplest artificial filtration system is marine mammal system, with different levels of filtration
- Dump and fill- similar to human swimming pools, may be brine or chlorination, some use marine mammal mix that more closely mimics ocean water (sodium chloride, magnesium sulfate and magnesium chloride)
- Mechanical filtration
- Ozone with chlorine/bromine
- Ozone without chlorine
- U.V. sterilizer
- Most complicated involve fish (+/-birds, reptiles) was water quality is imperative for resp
- No chlorine or bromine with fish.
- Oxygen-reduction potential (ORP) less than 350 mV when using ozone
- Biological filtration
- Gas exchange/partial pressure
- Foam fractionation
- Denitrification
- Invertebrates systems are even more complicated and detailed chemistry control needed
Traditional routes of water conditioning
- Gas exchange and aeration- large surface area-to-volume ratio allows good gas exchange with atmosphere (normal with large natural bodies of water)
- Artificial systems- maintaining natural balance of dissolved gases in systems critical to support bio filtration, maintain plant photosynthesis and animal respiration, maintain pH, and prevent supersaturation
- Try to maintain natural ratio to of O2/N/CO2- 1/2/4
- Primary components in artificial systems for gas exchange- diffuser stones, degas chambers (trickle filters), and venture injectors
- Surface skimming used to remove mostly dissolved organics at surface of tank
- Hinder gas exchange there
- Surface skimming used to remove mostly dissolved organics at surface of tank
Filtration methods
- Organic and bacterial loads important in filtration
- Closed recirculating systems- completely dependent on human manipulations to condition water and sustain life
- Filtration is designed to reduce overall organic and bacterial loads in a system
- Mechanical filtration
- Divide into large, medium, fine and dissolved materials
- Large particulate removed by a prefilter (screens and baskets)
- Medium particulates removed by pressure sand filtration or canister filters
- Fine particulates removed by flocculation- use with caution as effects on fish and invertebrates are not completely known
- Flocculation- method of using chemicals to bind particulates to make them bigger and easier to remove.
- Dissolved organics may also removed by activated carbon
- Foam Fractionation- particulates brought together mechanically by causing flow conditions that promote particle collisions
- Water slowly pushed down column with air injected at bottom of column, creating steady upward stream of very small bubbles
- Mucopolysaccharides produced by bacteria and algae stick together
- Safer alternative to flocculation
- Contact with air bubbles- form an organic film on surface of bubbles
- Resulting foam skimmed and flushed to drain, removing organic waste
- Biological filtration: unnaturally large populations of relatively few species of bacteria encouraged to convert organic waste products and nitrogenous toxins (ammonia and nitrite) to less toxic waste products (nitrate, phosphate, co2 and bio inert organic compounds)
- Causes yellowing of aquarium water
- Bacteria competes with fish and invertebrates for oxygen
- Denitrification- anaerobic two-step process, reactions catalyzed by specific bacteria reduce NO3−2 and release N2 as gas from system
- Dissolved oxygen = DO is the most common limiting factor to biological filtration
- Important biofilter design considerations
- Surface area (optimal is 2-5 ft2/gallon)
- Amount of solid buildup
- Gas exchange properties
- Water flow distribution over biofilm
- Packing – how media compresses w/in filter which affects water distribution through filter
- Backwashing requirements
- Uniformity and stability of biofilm populations
- Biomass shearing
- Water channeling – abnormal distribution of water allowing bypass of majority of media
- Ecological filtration
- Natural process where balance populations of bacteria, turf algae, phytoplankton, zooplankton, and other microorganisms interact with each other within specialized physical environment to form ecosystem that completely cycles and/or removes waste products in aquarium while enriching aquarium with oxygen, buffering pH and balancing water chemistry
- Sterilizing and disinfectants
- Sterilization
- Point contact sterilization- water diverted in sidestream in continuous contact with sterilizing agent and recycled back to system (inline UV radiation and ozone)
- Bulk fluid sterilization- oxidizes organics and kills microorganisms throughout water system (chlorine)
- Chlorine/bromine use in water systems regulated by APHIS
- Not to be used in systems housing fish
- Chlorine can be neutralized with sodium thiosulfate
- Activated carbon can also remove chlorine – must be replaced frequently
- Dissipation of chlorine not reliable as it takes 20 hours for each 1mg/L of chlorine
- Chloramine is a stable product of chlorine and ammonia – TOXIC to fish
- Sodium hydroxymethanesulfonate neutralizes chloramine
- Sterilization
- Ozone (O3)- allotrope of oxygen
- Highly oxidative and good for water sterilization and clarification
- Not very stable, dissipates readily
- Must be generated onsite
- Silver and Copper- together create bactericidal and fungicidal treatment
- Best in soft water
- EPA limits are silver 100 ppb and copper 1000 ppb.
- UV sterilization- radiation in range 254-nm to irradiate pathogens and proteinaceous debris
- Best to use in flow through system
- Tubes need to be changed every 6 months
- Water Conditioning for Marine Bird–Only Systems
- Freshwater systems with routine water changes to decrease oxidation demand on disinfectants
- Option only if not marine taxa will not be sharing with fish, reptiles, or mammals
- Heat exchangers- best if placed last in water handling system just before water reenters exhibit to be most efficient
- Must be sized correctly for the temp range of species, size and flow rate and thermal characteristics of the system
- Select one with water contacting components that are nontoxic, no heavy metal leaching
3
Q
Describe the proper protocol for collecting a water sample for water quality testing.
What are the minimum parameters that should be tested for water quality.
What are the most common water quality issues?
A
Minimum parameters: temperature, salinity, nitrogenous wastes, pH, hardness, alkalinity, dissolved gases +/- anions, cations, heavy metals, turbidity, microbiome
- Consider accuracy, sensitivity (detection limits), calibration and maintenance requirements, ease of use, cost of purchase and maintenance, durability, reliability in working conditions, and associated disposal requirements (such as reagents)
Most likely issues
- Source water - low DO, inappropriate temp, incorrect composition of salt mizes, high chlorines in municipal water, high iron in well water
- System water - high nitrogenous wastes, pH change in low-pH systems, temp change in tropical fish systems, oxidative by-products and low iodide insystems with ozone disinfection, drug assays
- Discharge water - drug residues, temp, salinity, pathogen load
- Transport water - low DO, high ammonia, inappropriate temps
4
Q
Describe how the water source may affect water quality.
What are some advantages and disadvantages of using municipal water, surface water, or ground water?
A
Water source
Municipal water - tap water
- Often requires treatment to remove chlorines and chloramines
Surface water - ponds, streams, rivers, lakes, seas
- Often requires filtration and disinfection to reduce particulates and pathogens
Ground water - wells, springs, aquifiers
*Any source water may require temperature correction
5
Q
Describe the effects of low dissolved oxygen on fish.
How is DO tested?
When should it be tested?
What are the target values?
What are some causes of low DO?
Is warm or cold water more likely to be affected?
How does DO vary throughout the day in a pond?
A
Dissolved Oxygen
Low DO - common cause of acute m&m in fish, can damage microbial population supporting biological filtration leading to increases in toxic nitrogenous waste
- Test continuously or routinely as positive aka daily, can vary across the year esp surface water
- Establish baselines across all seasons
- Check prior to and during immersion treatment, restraint, or transport
- Measure in multiple locations (varies with depth, water flow, and surface water agitation)
- Test using a DO meter: oxygen-permeable membrane, uses oxygen-dependent chemical reaction with electrical current measured by polarographic or galvanic electrodes
- Polarographic models require probe to be moved through the water
- Fiber-optic units measure the effect of oxygen on fluorescence
- Calibration is required each time it is turned on usually against moist room air, membrane should be replaced periodically or if there are tears or bubbles
- Measured in mg/L = ppm or as % saturation (amount required to saturate water varies with temp and salinity
- Target 6-15 mg/L or >90% saturation *some fish may be tolerant of lower levels but nitrifying bacteria in biological filters require >80%
- Low: <2-4 mg/L likely to cause morbidity and mortality in most species
- Often due to poor water flow, reduced photosynthesis, high organic loads
- More problematic in warm water because of low solubility and for pelagic and reef fish because of higher O2 demands
- High: rarely a problem, theoretically could cause O2 toxicity and gill damage, safe upper limit 120-140%
- Varies significantly across the day especially with vascular plants, algae, or phytoplankton which produce O2 during daylight through photosynthesis but consume oxygen overnight, lowest DO at dawn
- Oxygen is more soluble at lower temperatures
6
Q
What does the total gas pressure (or total dissolved gasses) measure?
What are the effects of high TGP?
Which gas is most likely to cause issues? Why?
How is TGP measured? What are the target values?
What values are likley to cause pathology?
What are the typical causes of high TGP?
A
Total gas pressure (TGP; total dissolved gasses, TDG) - partial pressures of O2, nitrogen, CO2, argon
- High: supersaturation, when total partial pressures is > atmospheric pressure → causes gas emboli and pathology in vasculature, eyes, or subcu spaces in fish
- Nitrogen is the most likely to cause gas emboli because its insolubility makes it more likely to come out of solution within the fish
- Get baseline for every system, monitor continuously in intensive systems
- Must be measured on site in the system, uses TGP meters (saturometers)
- Keep in water for >30 min (takes time for gasses to diffuse across membrane), best to track over at least 24hr to look for transient increases
- mg/L and %saturation relative to atmospheric pressure of air at the water surface
-
Target 90-100% or <105%
- High TGPs: gas emboli in fish, >110% likely to cause pathology; often due to entrainment of air into a pump or valve due to a crack or leak upstream, turbulent water flow (esp at depth), or poorly designed gas-exchange towers
- Single TGP values less useful than serial monitoring
- Low: unusual, may be associated with low DO or low water flow, warrants investigation
7
Q
Discuss the monitoring of temperature as part of water quality.
How do thermoclines develop?
How quickly can temperature change safely?
How does increasing the temperature of a system lead to more toxicity?
A
Temperature - cooler water is heavier than warmer water so steep temp gradients (thermoclines) can develop in deep habitats
- Assay continuously or at least daily, when fish moved between bodies of water, during restraint and transport
- Use thermometers certified by National Institute of Standards and Technology in the US), check accuracy and precision, min and max should be reported
- Species preferred temp zones
- Tropical reef fish: 22-28C (72-82F)
- Goldfish, koi: 15-22C (59-72F)
- Atlantic salmon, rainbow trout, other cold water spp: 7-18C (45-64F)
- Generally shouldnt change by >2C/hr or 5F/hr
- Increased temp in a system with high ammonia or heavy metals shifts chemical equilibrium to more toxic forms and m&m become more likely
8
Q
Describe the measurement of salinity as part of water quality monitoring.
How is artificial saltwater prepared?
How often should salinity be measured?
How is it measured?
What are typical values for freshwater and for saltwater?
What are some causes of low salinity?
What are some causes of high salinity?
A
Salinity - concentration of dissolved ions in water, mainly sodium and chloride in seawater, also calcium, magnesium, sulfur, potassium, and other inorganic elements
- Ions increase density of water and make it easier to conduct an electric current so salinity can be indirectly measured by specific gravity and electrical conductivity
- Artificial seawater typically made from dechlorinated municipal freshwater with added salt mixtures
- Avoid commercial mixes with sodium chloride alone and anticaking agents
- Phosphates rarely required in salt mixes for established aquariums because levels accumulate from food fed
- Bromides are less common in salt mixes recently, not required at levels seen in natural seawater and can form harmful residual oxidants with ozone disinfection
- Salts should be mixed in off-exhibit tank, not added directly to a system
- Salts are often a significant part of the cost of a marine aquarium
- Ions can be removed from freshwater by deionization, reverse osmosis, or distilling
- Test incoming water routinely or with production of each batch, test every 2-4 weeks if stable
- Full cation analysis (Na, Ca, Mg, and other ions) should be considered periodically
- Can be stored for a few days at room temp or weeks refrigerated or frozen
- Refractometer or hydrometer to measure specific gravity - reflects total dissolved solids but gives a quick approximation
- USG usually 1.005-1.030, conversion tables available for temperature correction
- Handheld conductivity meters more accurate indirect measurements of salinity (salt water) or total dissolved solids (freshwater)
- g/L = ppt or practical salinity units (psu; roughly equivalent to g/L)
- Freshwater systems - electrical conductivity may be reported in uSiemens/cm or umho/cm
- Seawater often 32-35 g/L; freshwater <0.5 g/L or conductivity 60-2000 uS/cm
- Ion-exchange chromatography is used for cation analysis
- Low salinity may be caused by freshwater contamination, insufficient salt added, or crystallization of salts on lids/life support system components (“salt creep”)
- High salinity: evaporation or contamination by salts or saltwater
9
Q
Describe the nitrogen cycle and how it affects fish.
What are the ammonia-oxidizing bacteria?
What are the nitrite-oxidizing bacteria? Where are they found?
Which form of ammonia is most toxic?
What are the two methods for measuring ammonia? When should they be used?
What about nitrite? Is it more of an issue in FW or SW fish? Why?
At what level does nitrate become an issue?
How frequently should these tests be run?
What are target concentrations for these products?
A
Nitrogenous wastes: Ammonia, Nitrite, Nitrate
- Nitrogenous wastes are produced through protein metabolism by animals and decay processes (excess food or dead plant matter)
- Nitrogen cycle: conversion of ammonia → nitrite → nitrate
- Ammonia-oxidizing bacteria: betaproteobacteria, gammaproteobacteria (Nitrosomas)
- Nitrite-oxidizing bacteria: Nitrobacter, Nitrococcus, Nitrospina, Nitrospira spp.
- Nitrifying bacteria exist on all surfaces within the habitat but are concentrated where surface area is high (sand filters, undergravel filters
- Uses oxygen and alkalinity, produces CO2 via bacterial respiration
- Ammonia: ionized (NH4+) and unionized (NH3) = total ammonia nitrogen (TAN)
- *Un-ionized more toxic to fish as it can diffuse across the gills
- Increase in toxic form (un-ionized) at high pH, high temp, and low salinity
- Nitrite can be toxic to fish in freshwater systems
- colorless adn odorless, toxic at 0.10 mg/L in freshwater
- Binds hemoglobin (methemoglobinemia)
- Chloride cells transport nitrite as well (nitrite to chloride ratio dependent, so less of an issue in SW)
- Nitrate is a stressor and endocrine disruptor
- Can disrupt hemtologic factors when >100 mg/L
- Nitrate is removed from the system though water changes, algal or vascular plant use, and denitrification systems
- Assay ammonia and nitrite on all systems q1-2wks in stable systems: daily in new systems, when new fish are added, or following immersion treatment
- Nitrate testing often less frequent, q1-2mo
- Samples for ammonia and nitrite can be stored for a few hours at room temp, up to 24hr if refrigerated, 48 hrs if frozen
- Nitrate more stable, can store samples longer
- Commercial test kits for ammonia:
-
Nessler method - rapid and reliable in freshwater, less accurate in salt water
- May be falsely elevated within 24-72hr of treatment with formalin or ammonia-locking compounds (often contain formalin)
- Includes mercury which must be disposed of as hazardous waste
-
Ammonium salicylate method - more accurate in salt water if using modifying reagent developed by Kingsley
- Produces sodium nitroferricyanide - often requires disposal as hazardous waste
- Not affected by presence of formalin
- More expensive, slightly slower
- Ion-specific electrodes for measuring ammonia, have to know water temp, pH, and salinity
- Nitrite and nitrate tests: colorimetric, assayed with colorimeter or spectrophotometer (more accurate)
- TAN reported in mg/L; un-ionized ammonia calculated from TAN using conversion factor based on temp, pH, +/- salinity
- UIA < 0.02 mg/L
- Nitrite-nitrogen <0.1 mg/L
- Nitrate-nitrogen <50 mg/L for most fish (<15 mg/L for may inverts)
- High ammonia followed by high nitrite often seen in newly established recirculating systems in first few weeks after animal additions until there are sufficient nitrifying bacteria to handle the bioload.
- High nitrate is seen in long-established recirculating systems without denitrification or adequate water changes or with system contamination such as nitrogenous fertilizer
- Increases more likely to be problematic in warm water and freshwater systems because of higher unionized (toxic) form of ammonia
- Low levels are never a concern for fish but vascular plants and algae need nitrate for healthy growth
-
Nessler method - rapid and reliable in freshwater, less accurate in salt water
10
Q
What are the target pH values for freshwater adn saltwater?
What is an effect of increased pH? When is this most clinically relevant?
How does it vary with the day? When is it the lowest?
A
pH - concentration of hydrogen ions on a logarithmic scale
- Test incoming water regularly or with each production batch, test stable systems every 2 weeks
- Samples cannot be frozen and assaye slater
- Colorimetric tests common but accuracy often +/- 0.5
- Handheld pH meters use electrometric or potentiometric methods - more accurate and readily available, must be calibrated
- Freshwater: target pH 5.5-7.5
- Saltwater: target pH 7.5-8.5
- New concrete can leach materials that affect pH
- Increases in pH increase toxic forms of ammonia and heavy metals, most clinically relevant with closed transport containers when plastic bags are opened post-transport and accumulated CO2 escapes causing water pH to increase and high levels of ammonia in the transport water to become more toxic
- pH can vary significantly across the day because of diurnal changes in animal and plant respiration and photosynthesis, esp heavily planted systems - pH values are lowest at dawn
11
Q
What do alkalinity and hardness measure?
Low alkalinity can increase what toxicity? How does this occur?
How are these values measured?
What are the typical values in a FW system?
What about a SW system?
How do changes in these values occur?
A
Alkalinity - concentration of anions or bases in water: bicarb (HCO3-) and carbonate (CO3 2-), also hydroxide (OH-), borate (BO3 3-), and phosphate (PO4 3-)
- Measure of buffering capacity, high alkalinity helps to limit rapid changes in pH
- High alkalinity is often associated with high hardness and high pH but not always true
- Test system alkalinity every 2-4wks, prior to copper sulfate immersion (low alkalinity increases risk of toxicity)
Hardness - concentration of divalent cations: Ca2+ and Mg2+, also strontium (Sr2+), ferrous iron (Fe2+), and manganese (Mn2+)
- Monitor hardness in rearing systems - inappropriate hardness can affect egg hatchability and fry survival
- Samples can be stored for a few days at room temp or few wks when refrigerated
- Commercial colorimetric test kits: EDTA titration, atomic absorption spectrometry
- Spectrophotometric testing for specific anions or cations may be considered in specific systems
- Calcium in hard coral and egg or larval-rearing systems
- Ferrous iron in well water
- Phosphates in hard coral systems, outdoor ponds where increases (from fertilizer) can cause algal blooms, and long-established closed systems where phosphates from food builds up over time
- Hardness and alkalinity measured in mg/L of CaCO3 or mEq/L CaCO3
- mEq/L x 100 = mg/L CaCO3
- Freshwater may be soft (hardness 40-75 mg/L or 2-4dH) or hard (hardness 75-150 mg/L or 4-8dH); alkalinity 50-200 mg/dL
- Saltwater usually high hardness (150-300 mg/L or 8-16 dH) and high alkalinity (>200 mg/L)
- Possible target range for free calcium is 25-100 mg/L
- Most common problem: gradual decrease in alkalinity in closed system as ions are used by animals, buffers and salts routinely added to compensate
-
Also affected by addition or removal of salts such as oyster shell (CaCO3), calcitic limestone (CaCO3), dolomitic limestone (MgCO3 and CaCO3), hydrated/slaked lime/limewater (Ca(OH)2), sodium bicarb (NaHCO3), sodium carbonate/soda ash (NA2CO3), and calcium chloride (CaCl2)
- May be part of substrate (crushed coral), decor, or enclosure walls (concrete)
- Low alkalinity increases risk of rapid pH changes; low alkalinity and hardness increase the dissolution and absorption of heavy metals
- Copper sulfate treatment is contraindicated in low alkalinity because of the possibility of rapid pH changes
12
Q
What affect does dissolved carbon dioxide have on water quality?
What is a target concentration?
What are some effects of higher levels? When does this commonly occur?
A
Carbon dioxide - very dynamic
- Highly soluble, produced by animal and microbial respiration and decay processes, used during photosynthesis
- Reacts with water to form carbonic acid (H2CO3) which dissociated to bicarbonate (HCO3-_ then carbonate (CO3 2-), and hydrogen ions (H+) depending on alkalinity, pH, salinity and temp
- Testing is not common but usually done in high-risk situations
- Measured on site and within 30 min of sampling
- Commercial colorimetric tests, can be estimated based on pH and alkalinity using standard curves
- Narrow range of pH in salt water (7.5-8.5) means low pH may indicate high levels CO2
- mg/L; common target < 20 mg/L
- High CO2 affects pH and O2 availability, common in intensive aquaculture systems with limited off-gassing, closed transport containers, well water, and after algal or phytoplankton die-off
- Low levels not a health concern for fish but vascular plants, algae, and phytoplankton need CO2 for photosynthesis
- CO2 is inversely related to pH and is a component of alkalinity which affects pH stability
- CO2 can vary significantly across the day because of diurnal changes in respiration and photosynthesis, highest at dawn
13
Q
What are the various forms of chlorine in water? Which are toxic?
What is the difference between free and total chlorine?
When are these values measured?
What shoudl the values be?
How do high levels occur?
How are high levels managed?
A
Chlorines and chloramines - toxic to fish and invertebrates (not to be confused with chloride)
- Chlorines: oxidants that are highly reactive
- Chlorides: essential salts to fish
- Chloramines: chlorines bound to ammonia *no direct test for chloramines
- Chlorines and chloramines frequently used as a disinfectant in municipal water, can be present in tap water at levels that can be toxic to fish (0.5-3 g/L) *must be removed
- Also accidental exposure to bleach or similar disinfectants
- Ozone disinfection can convert chlorides (and bromides) in water into strong oxidants and oxidative by-products *should be confined to ozone contact chamber and not released into the fish habitat
- “Free chlorine” - sum of active oxidants (Cl2, OCl-, and HOCl)
- “Total chlorine” - sum of free chlorine and combined chlorine (chloramines)
- Assayed where they are considered a risk: incoming municipal freshwater before and after carbon filtration or other treatment to ensure chlorines have been removed; with ozone disinfection test for residual oxidants including free and total chlorine (and free and total bromine)
- Regular testing more useful than individual results because of margin of error inherent in many of the test methods
- Any tap-water contamination will artificially increase results
- Testing by colorimetry or potentiometry
- Measured in mg/L - total chlorines should be <0.03 mg/L for most fish, <0.01 mg/L for sensitive species
- High levels of chlorines or chloramines are toxic to fish, most often from untreated municipal water or failure of dechlorination methods
- Management: water changes, aeration, addition of activated carbon filters, or treatment with sodium thiosulfate, UV light, or binding products such as AmQuel
14
Q
What are the various forms of iodine in water? Which forms are usable?
How does ozone affect it? What about nitrate?
What are target levels for elasmobranchs?
What levels do they need to be below?
A
Iodide and iodate
- Iodine (I2) - essential micronutrient, exists in water as iodide (I-), iodate (IO3-), and dissolved organic iodine
- Iodide and dissolved organic iodine are considered bioavailable, can be oxidized to iodate (no available to fish)
- Deficiencies associated with goiters esp elasmobranchs
- Iodide and iodate should be assayed routinely in elasmobranch systems esp where ozone disinfection is used
- Samples can be stored for a few days at room temp or wks when refrigerated or frozen
- Iodide assayed with high-performance liquid chromatography
- Can be hard to measure accurately if nitrate levels are high
- Measured in mg/L = ppm or umol/L
- Salt water with elasmos: iodide target levels 0.03-0.06 mg/L
- Low iodide: esp in long-established recirculating systems with ozone disinfection: ozone converts iodide to iodate
- Unknown if excess iodide leads to thyroid dysfunction in fish as it does in other classes, levels should be kept <0.1 mg/L
-
Iodine – functions as component of thyroid hormones
- Deficiency is common cause of goiter in elasmobranchs
- Ozone reduces bioavailability – the usable iodide is oxidized to unavailable iodate. High nitrate also reduces iodide uptake
15
Q
What are some potential heavy metal toxins to fish?
What should these levels typically be below?
What are some potential causes of heavy metal exposure?
When is toxicity more likely?
A
Heavy metals - potentially toxic to fish, particularly common where surface or ground water is used
- Potential toxins: copper, zinc, lead, mercury, manganese, and arsenic
- Test based on risk analysis, samples can be stored for weeks or months if frozen
- Commercial colorimetric tests can be used for copper and iron but heavy metals best assessed using spectrophotometer; most other tests rely on atomic absorption spectrophotometry
- Reported in mg/L = ppm or ug/L = ppb
- Important to differentiate free/ionic concentration (more toxic form) and total (free + combined/chelated)
- Generally should be <0.03 mg/L for most heavy metals
- Common causes of high heavy metals: copper sulfate treatment, contaminated source water, drip contamination of system, or leaching from decor, substrate, enclosure walls, or water lines
- Toxicity more likely at low pH, hardness, and alkalinity and at high water temps
18
Q
What is the most common environmental problem of fish?
What is the target dissolve doxygen concentration?
How does that vary with water temperature? How does DO vary throughout the day in a pond?
What are some causes of reduced DO?
What fish are most susceptible? Which are more resistant?
What clinical findings would you find on exam of affected fish?
What differentials should be considered?
How is this diagnosed?
How is it corrected and prevented?
A
- Low DO
- Most common envtal problem of fish
- Target DO is >90% (6-18 g/L depending on salinity and water temp)
- Initiate husbandry changes rapidly to correct this
- Etiology
- Almost all fish rely on O2 in water, except a few obligate air breathers
- DO comes from plants, diffusion from air and water movement
- Causes: low aeration or water flow, high water temp/salinity, high organic load, stocking density, heavy feeding, small SA or water volume, immersion tx (formalin), granular activated carbon, reduced photosynthesis (at dawn after an algal die off in fall and winter *cloudy days in fall - ponds), ice cover over shallow ponds, high altitude, reversal of thermocline in lakes or ponds after wind, rain, thunderstorms
- Signalment
- Most- esp Salmonidae, tropical marine teleosts, elasmos
- More resistant spp - tilapia, crucian carp, goldfish, epualette sharks, facultative and obligate air breathing fish
- Larger fish more sensitive than smaller fish
- Clinical Findings
- Lethargy, inappetence, dyspnea or tachypnea (fared opercula, piping or gasping at surface or gathering in high areas of flow), blotchy skin in sharks, color changes in water, stagnant look to water, acute mortality of 100%, multiple species affected
- DDX:
- Ammonia toxicity, contaminated water, acute ectoparasitic or bacterial disease
- DX:
- Measure DO with a DO meter, calibrate every time first. Normal 90-100%
- Husbandry
- Increase aeration stat - air stones (less efficient), fine pore stones producing small bubbles > big bubbles. Provide direct aeration from O2 cylinders, liquid O2 or oxygen generators. Packed column aerators, aeration cones and Venturi oxygen injectors considered if long term needed.
- Check the life support system
- Minimize stressors
- Reduce feeding temporarily
- Remove unnecessary organic material
- Monitor ammonia and nitrite levels which can be affected
- Prevention
- Measure DO on routine basis
- Predict DO in outdoor ponds for the morning; measure at dusk and 2-3 hrs later, if extrapolation shows it falls too low at dawn, increase aeration
- Aerators on timers to provide addl aeration overnight, or turned on when DO is below a limit
- Power outages - use battery powered or generator powered air pumps, withhold food, have water available for water changes
- Monitor algae at surface
- Environmental hypoxia (Noga):
- Low DO.
-
Temp and salinity have a significant influence on O2 solubility.
- Higher temp, higher salinity = lower total O2 dissolved in water.
- Photosynthesis most important source of O2 in ponds.
-
Marked diurnal variations.
- O2 highest at sunset, net O2 production occurs during day.
- At night, O2 declines (no photosynthesis).
- Plant respiration continues, O2 is used up overnight and lowest levels are before sunrise.
- Warm water also decreases O2 solubility, so O2 lowest in ponds in summer.
- Algae major producers and consumers of O2 in ponds.
- Cloudy water may reduce photosynthesis/overcast weather.
- Massive death of algae can cause severe O2 depletion. Decaying O2 demands O2.
- Chemicals used to tx fish disease i.e. copper sulfate, potassium permanganate, formalin are algicidal.
- Ice formation can also deplete O2.
- Prevents O2 diffusion into pond and blocks photosynthesis while respiration of pond organisms continue.
-
Temp and salinity have a significant influence on O2 solubility.
- Due to overcrowding, low water flow in raceway, algae crash in pond, several overcast days over pond.
- Acute mortality of all but air-breathing fish, fish piping, gathering at water inflow, death with opercula flared and mouth open (agonal response), large fish die (small may survive). Chronic environmental hypoxia can cause stress.
- At least 5 mg/l of DO is needed for optimal growth and reproduction of most fish. Goldfish tolerate anoxia. Chronic hypoxia can also cause immunocompromised, ulcers.
- Tx: Restore O2 levels.
- Monitor ammonia and nitrite for 1 wk to ensure biological filtration is functioning properly.
- Aeration, can transfer water from adjacent ponds.
- Check algae concentrations.
- Dx can only be done by on-site DO measurement, otherwise not accurate.
- Differentiate environmental hypoxia from nitrite toxicity and gill parasitosis.
- Low DO.
19
Q
Describe the effects of gas supersaturation in fish.
This disease is common in what settings?
What are the common causes?
What fish are more susceptible?
What are the clinical findings you may find on exam?
What differentials need to be consider?
How can this disease be confirmed?
What husbandry considerations need to be made?
What medical treatments can be used?
A
Gas Supersaturation (CGFM)
- Sum of gas pressures in water is higher than atmospheric pressure
- A cause of gas bubble disease
- Common in aquarium fish, following gas entrainment into a pump, in cold-water aquaculture where gas pressures are kept high. Prognosis good if supersaturation can be resolved.
- Etiology
- Increased partial pressure of dissolved gases, Nitrogen MC since that gas is more soluble and abundant > CO2 >> O2 (rare, causes oxygen toxicity or gill damage)
- Entrapment of air into a pump from a leak or crack upstream, rapid increase in water pressure or temperature, excess supplementation of gases, turbulent water flow or entrainment of air across pressure differentials i.e. life support equip on diff floors, waterfalls, water sourced from deep wells, springs, unusually high levels of photosynthesis
- Signalment
- All spp susceptible, larger and more active bony fish most likely
- Clinical Findings
- Multiple spp affected
- Exophthalmos, buphthalmos, corneal edema, intra/periocular gas, anterior lens lux or cataracts, skin darkening, focal pallor in sharks, gas bubbles in skin or fins, bubbles in brood pouch in seahorses
- dyspnea/tachypnea common
- Lethargy, increased activity, positive or negative buoyancy (due to swim bladder changes), reduced appetite, mortality can reach 100%,
- intraocular gas is slowest to resolve - cataracts and ophthalmitis common sequelae
- DDX: barotrauma, perimortem period (moribund fish on a skimmer or turbulent water), intraocular gas from infx or inflammatory processes in the eye
- DX:
- Gas emboli - PE, gill or fin bx; emphysema on necropsy, gas emboli or hemorrhage in any tissue;
- measure total gas pressure (TGP) using a TGP meter where the fish are found in the system, ideally monitor trends. >103% suspicious, >110% likely to cause acute lesions
- If no TGP meter, DO >100% suspicious
- Husbandry
- Check life support system for cracks, salt deposits
- Minimize handling, agitate surface water to promote off-gassing, incr water depth to reduce gas pressures, consider slowly reducing water temp if tolerated,
- consider recompression tx of individual fish to >1atm for 6-24 hours followed by gradual decompression over several hours or days
- If incoming water is supersaturated, well designed degassing towers are likely required
- Medical tx
- Aspiration of free gas in the eye, coelom, or pouch; recurrence if source not removed is common
- Acetazolamide - Carbonic anhydrase inhibitor (reduced Co2 in the eys and plasma and may reduce O2 secretion), high doses - negative buoyancy, neuro signs, mortalities
- Consider systemic abx coverage
- Other tx reported - dorzolamide, systemic anti inflammatories
- Prevention
- Routine TGP measurements, life support system design, degassing towers with large or intensive systems, large habitats with variable depths
Problem 11 – Gas Supersaturation (Noga)
- Prevalence: WF - 4, WM - 4, CF - 3, CM - 4
- Epidemiology/Pathogenesis:
- Edema of secondary lamellae, vacuolar degeneration of renal epithelium, edema/embolization of mucosal surfaces
- Diagnosis:
- Total dissolved gases, clinical history, gross lesions
- Gas emboli in gill capillaries
- History:
- Rapid increase in water temperature, water intake pipe sucking in air, rapid decrease in pressure, behavioral abnormalities in the fish, fish floating to the surface
- Physical Examination:
- Gas emboli in gills, skin, fins, rays; exophthalmos
- Treatment:
- Agitate water to volatilize excess gas; caused by water supersaturated with gases, due to pump malfunction, cold water heated quickly, submerged hoses, algae overgrowth, pump malfunction
Miscellaneous.
- Gas bubble disease/supersaturation.
- Total pressure dissolved gasses exceeds barometric pressure.
- Gases drawn or injected into water i.e. pumps, small leaks and vortices, artificial waterfalls.
- May also occur due to utilization of well water without off-gassing/when heated to higher temps.
- CS – gas embolism, emphysema in any organ.
- Most commonly in gills, exophthalmos, intraocular.
- On histo gas appears as colorless areas, choroidal rete or retrobulbar, may have granulomatous inflammation.
- High morbidity/mortality.
- Survivors may have persistent neuro signs, blindness, generalized debilitation, persistent exophthalmos.
- Evaluation of gas saturation of enclosure water.
26
Q
Describe the effects of ammonia toxicity on fish.
What is the most toxic form of ammonia?
What are the causes of high ammonia?
What fish species are particularly sensitive?
What clinical findings would you find on exam?
How is ammonia toxicity confirmed? What lesions would be present on pathology?
What husbandry changed can be made to improve the water quality?
What treatments can be made to the water?
How is this best prevented?
A
-
Ammonia Toxicity (CGFM)
- Unionized form is more toxic, highest in warm freshwater
- Nitrogenous waste product of most fish, can buld up if not oxidized by nitrifying bacteria ro removed via water changes
- Etiology
- Sources of ammonia: protein waste products, bacterial fermentation, organic decomposition; municipal or groundwater; leaching of fertilizers, industrial emissions
- Ammonia builds up rapidly in closed systems or static (ie transport bags)
- Ammonia-oxidizing (nitrifying) bacteria convert ammonia to nitrite using DO and bicarbonate ions, grow on every surface
- Causes of inadequate nitrifying bacteria - immature systems, High stocking densities, high organic load (ie food), reduced H20 changes, acute envtal changes, low DO/alkalinity, high pH (>8)/temp, recent algal bloom die off, some abx (enro/erythromycin), some antiparasitics (formalin, chloroquine, levamisole)
- NH4+ (ammonium-ionized) and NH3 (ammonia - uniionized) are the two major forms, the latter is more toxic. Closed transport containers are a big risk, once opened, CO2 rushes in → pH incr converts NH4+ to NH3 → rapid ammonia incr
- Signalment
- Tetras and salmonids esp sensitive; air breathing spp more resistant
- Clinical Findings
- Acute - lethargy, inappetence, dyspnea/tachypena, erythema, incr mucus, dark coloration, neuro signs (erratic swimming)
- Chronic - wt loss, reduced feeding, poor growth rates, some acute signs may be seen
- Secondary infx common, incr in nitrite common
- DDX: other envtal failure (low DO, contaminated water), ectoparasitic or bacterial dz
- DX:
- Testing the water (ammonia colorless, odorless. Most kits test total ammonia nitrogen, the NH3 should be calculated based on pH and temp (see table)
- NH3 (unionized ammonia; UIA) should be <0.02 mg/L, toxic if 0.5-1 mg/L
- Husbandry
- Incr aeration (target 95-100%)
- Change 30-50% of water daily, remove excess organic material, reduce or stop feeding temporarily, check life support system, consider new source of organic carbon (i.e. chopped hay) as carbon can be a limiting nutrient for nutrifying bacteria
- Consider adding substrate from another system with nitrifying bacteria
- FW: consider adding zeolite to adsorb ammonia
- Consider moving all of the fish
- Ammonia is NOT removed by activated carbon
- Medical tx
- Commercial products that bind ammonia are available (i.e AmQuel); ammonia tests will remain high b/c they do not remove it
- 1-3 g/L of salt in FW can reduce physiologic stress
- Prevention
- Test 1-2x/week in most systems, any ammonia should prompt response
- Maintain DO and alkalinity within appropriate ranges
- Mature biofilters in new systems with ammonium chloride or urea for 3-8 wks
- If no cycling is possible prior to adding fish, the stocking density must be very low with fish relatively tolerant of ammonia
- Maintain biofilters without fish and feed NH3Cl or urea as ‘biofarms’ as a source of nitrifying bacteria
- Fast fish prior to shipping
- Ammonia poisoning (Noga):
- Lethal poisoning > 1.00 UIA/L
- Sublethal poisoning > 0.05 mg UIA/L
- Hx – Overcrowding, recent meds or chemicals, newly established tank, aquarium gravel or filters recently cleaned or changed, failure of bio filters, recent algal crash in pond, reduced water flow in raceway, hyperexcitability, other neuro signs if acute > 0.2 mg/L; acute to chronic stress.
-
Tx – 25-50% water change in aquarium; add zeolite; add buffer to FW to reduce pH; add nitrifying bacteria; add bio filtration; decrease density; temp reduce or stop feeding.
- Ponds or flow-through systems – Stop or reduce feeding, decrease density, add water or increase flow.
- Ammonia is the primary nitrogenous waste product of fish, also from decay of proteins.
- Aquaria – Inadequate number of bacteria oxidizing ammonia to nitrite.
- Nitrosomonas europaea – predominant ammonia oxidizer.
- Aka AOB – scarce in new aquaria, ammonia rises rapidly when fish added.
- Aka new tank syndrome.
- Can also occur in long-established tanks.
- Overfeeding or adding too many fish to tank.
- Overwhelms biofilter.
- Bio filter and ammonia removal will be greatest where there is a high water flow over a large surface area.
- Cleaning filters will also result in ammonia spike when bacteria are removed.
- Overfeeding or adding too many fish to tank.
- Aka AOB – scarce in new aquaria, ammonia rises rapidly when fish added.
- Nitrosomonas europaea – predominant ammonia oxidizer.
- Ponds – Most likely near sunset, when pH, temp, and unionized ammonia are highest.
- Algae and nitrosomonas bacteria major consumers of ammonia in ponds.
- Increases in fall and winter, possibly because of decrease in algal and bacterial metabolism at low temps.
- Ammonia may rise after algae crash.
- CS – anorexia, hyperexcitability, hyperplasia and hypertrophy of gills (not specific).
-
Two forms: unionized (NH3) and ionized (NH4+).
- UIA toxic to fish.
- High pH and temp and low salinity favors UIA.
- Concentration determined from chart.
- False positives when measuring ammonia via Nessler method if formalin is present. Salicylate method fails to measure ammonia (false negative) if formalin. Use an ion probe to measure if during formalin treatment.
- Tx – Water changes, zeolite (efficacy decreases with inc salinity), reducing pH will reduce percentage of NH3 (for each 1 unit pH decreases there is 10x decreases in UIA), ammonia-neutralizing products. Ultimately need to fix the biofiltration situation.
-
Ammonia toxicosis aka New Tank Syndrome (ZP).
- Common scenarios – adding new fish prior to appropriate development of filter bacteria; changing filters, biomedia removed in excess; high stocking densities, marginal filter microorganism capacity; overfeeding, protein breakdown and generation of ammonia.
- Risk factors – small water volumes, high animal densities, lack of appropriate microorganisms.
- Assessment of water ammonia levels diagnostic.
- Affected by pH, temperature.
- Unionized ammonia > 0.05 mg/L considered elevated, should be treated. > 1 mg /L rapidly fatal.
- CS – Range from no change to excess mucus production.
- Lesions – Edema, epithelial degeneration, fusion of gill lamellae.
- Severe cases – Alzheimer’s Type 2 gliosis.
