Princ of Aquaculture Exam 1

What is good water quality

minimum (cost effective) set of water-quality conditions that does not measurably constrain the cultured organism’s survival, health, or growth

What is good water qualtiy in the Aquaculture perspective

high nutrient loads can be beneficial, driving the natural food web in a carp pond

What should you consider when analyzing good water quality

• what is good for one fish can be bad for another

• can be better depending on life stage

What is the master variable in water quality

temperature

True or False: poikilotherms body temperature depends on their surrounding

True

Reasons why temperature is important for water quality

• controls rate of feeding, assimilation, growth, and reproduction

• increases ammonia toxicity

• changes viscosity and gas solubilty

How does the metabolic rate fluctuate with temperature

doubles or triples for every 10C increase

True or False: as water gets colder, it holds less DO

False: occurs when it gets warmer

True or False: because there is less DO available when water is warmer, fishes demand for it increases

True

What is the optimum temperature for coldwater species and an example

10-20C; ex: rainbow trout

What is the optimum range for warmwater species and an example

25-100C; ex: channel catfish

What occurs during the critical thermal limits

exposure causes loss of equilibrium and death within minutes

What occurs during incipient lethal temperature limits

can be tolerated for a longer period but will ultimately prove fatal

When is the spawining period for coldwater species

fall

What is the impact of thermal shock

causes acute stress, suppresses the immune system, and disrupts enzymatic funcition

Define the epilimnion

warm, less-dense, well-mixed, and usually oxgenated surface water

Define metalimnion (thermocline)

thin boundary layer, physical barrier to mixing

Define hypolimnion

cold, dense bottom water; consumes all oxygen, making layer anoxic

True or False: when in too high or low temperatures it is best to stop feeding fish due to stress or inability to digest food

True

What is the industries solution to climate change

focus on selective breeding for species with higher thermal tolerance

What are some solutions to temperature control

• using greenhouses to trap heat

• deeper ponds for cooler water

• geothermal wells for stable water in cooler climates

• chillers or heaters

Define salinity

total concentration of all dissolved inorganic ions in water

What occurs for electroneutrality

total cations=total anions

What is a challenge regarding salinity in freshwater

preventing ion loss

What is a challenge regarding salinity in seawater

preventing dehydration (water loss)

True or False: freshwater fish are hyperosmotic meaning they are losing more water to their surrounding

False: they are taking in more water and excreting a lot of urine

Define Stenohaline

organisms with a very narrow range of salinity tolerance

Define euryhaline

organisms capable of tolerating and adapting to a wide range of salinities

What is the issue with the formation of salwater in your kitchen for fish production

you are missing key ions like potassium, and magnesium in your mixture

True or False: you can trick marine fish like cobia into adapting to low salinty by injecting needed ions

True

What are tools to use for measuring salinity

• handheld refractometer-measure refractive light

• conductivity meter- measures electrical conductance

• hydrometer- measures specific gravity

How does light influence a fishes nature

drives their reproductive cycle

At what time does it become dangerous for fish and they are at risk of hypothermia

6:00am

Define photoperiodism

primary time giver that synchronizes internal biological clocks

What is an example of commercial application for photoperiodism

red drum broodstock are exposed to compressed seasonal light cycles to induce spawning year-round

How does light impact larvae survival

• rearing in darkness leads to mass non-inflation of swim bladder

• without it cannot detect live prey

• sudden changes in light can induce severe startle response

True of False: you need to account the type of filter you use based on types of waste that will acrue in the system

True: as tilapia feces can tangle in screens

What is hyperplasia and how does it occur

thickening of the gill tissue due to turbid water

What are methods used to measure turbidity

• secchi disk

• nephleometry-meaures light scattered at an angle

What does the yellow zone indicate when interpreting the reading for a fertilized pond

that it needs more fertilizer to help produce healthy algal blooms

What are the advantages of using the turbidometer

• eliminates observer bias

• essential for shallow tanks and hatcheries

What is the analysis related to blue-green waters

due to cyanobacteria, undesirable, associated with off-flavors. and potential toxin production

What is the analysis of brown water

caused by diatoms, excellent and prized for shrimp and shellfish hatcheries

What is the analysis for tea/coffee-colored water

concentration of humic acids and tannins, low productivity with tannis blocking entry of light

What are the common causes of gas bubble trauma

• rapid heating

• air entrainment from air pumps

• intenses photosynthesis (algal blooms)

Define scouring velocity

minimum flow required to keep solids suspended until they reach drains

How much dissolved oxygen is in the water and how does this compare to the air

-there is 0.001% in the water, with 21% in the air

How does altitude affect the amount of availble oxygen

lowere atmospheric pressure reduces oxygen saturation

What is the affect of the counter-current exchange in the gill

allows fish to extract up to 80% of the DO

Do smaller fish consume more oxygen per kilogram than larger ones

yes, although they don’t individually in groups they outcompete larger fish

Define specific dynamic action

the energy and oxygen cost of processing food

True or False: oxygen consumption can increase by 40-60% above baseline resting levels after fish have eaten

True

What is the optimum zone for oxgyen

7.0-9.0mg/L

When are oxygen levels lethal for fish survival

<1.5 mg/L

Define hypoxia

oxygen conditions that limit normal phsysilogical function

What is the second line of defense for hypoxia

• increased ventilation

• slowed heart rate (bradycardia)

• switch to anerobic metabolism

What is the bohr effect

decrease in blood pH;decreasing blood affinity for oxygen

What is the root effect

decrease in pH; reducing total oxgen carrying capacity

What consumes oxygen (night)

• plankton

• fish

• bacteria in sediment

When are oxygen levels at their lowest

near dawn

When are oxygen levels at their highest

in the late afternoon

What are the three types of mechanical aeration devices

• surface aerators

• diffused air (blowers)

• injectors (ventrui)

What is the best method for testing water quality

titration