Measuring Fish Respiration
A hands-on laboratory exercise
Megan Kepler
Why study respiration?
Energy in
Energy out
Metabolism
Consumption
Egestion
Excretion
Growth??????
Respiration
• Part of metabolism (active vs. resting)
– Easiest to measure resting in the lab with closed
chambers
– Function of gills, dissolved oxygen from water, role
of plants
– What do you think influences respiration rate?
• Temperature, fish size, activity, environmental
conditions, stress, etc.
Let’s get the lab started……
That way we have time to interpret some
the data…..
-Quantitative vs. qualitative experiments
Questions for thought
–How do respiration rates vary with fish
size? (Fish Physiology)
–How do respiration rates vary with
temperature? (Fish Physiology)
–Why could respiration rates be
important for fisheries management?
Overview of experimentation
• Respiration experiment
– Measure change in DO with a fish respiring in a
closed chamber for an allotted period of time.
• Experiment objectives
– Understand how fish respiration changes with fish
size and temperature
– Relate respiration experiments to fisheries
management, physiology, and aquaculture
Items you will need…..
•
•
•
•
•
•
Fernbach Flasks
Rubber stopper
Large Tub
Dissolved Oxygen Meter
Scale
If temperature change is desired….
– Ice/heater
Steps for laboratory setup
• 1.) Acclimate fish to test temperature
(ambient, heated, lowered)
Test temperature ~18°C (64.4°F)
-hold fish at this temperature prior
to experiment
Steps for laboratory setup
• 2.) Prepare water bath and Fernbach flasks
– Fill tub with test water prior to experiment
– Take initial Dissolved Oxygen reading
– Fill Fernbach flasks with water, measure volume
Fernbach
Flask
Water Bath
Dissolved Oxygen
Probe
Steps for laboratory setup
• 3.)Weigh fish and place in Fernbach Flask, top
off the flask with water and seal top with a
rubber stopper
– Record starting time
Other considerations for setup….
• Volume of flask
• Single fish vs. groups of fish
• Size of fish in relation to flask
• Multiple experiments on single fish (not sure if
time would permit in classroom setting)
• Fasting fish for a short duration
Experimentation
• 4.) Allow fish to respire for a period of time
(goal to achieve 1mg/L drop in DO)
– Amount of time depends on fish size and
temperature
• 5.) After allowing fish to respire, remove
stopper and measure DO
– Record ending time
Data collected
•
•
•
•
Change in DO (mg/L)
Volume of flask (L)
Fish Weight (g)
Time (day)
Specific Respiration Rate
i.e.) mgO2 consumed/gram
fish/day
Unit conversion  (mg/L *L) / g / day  mg/g/day
Example data
Tank
Weight DO_i DO_f ΔDO
Vol
(g) (mg/L) (mg/L) (mg/L) (L)
mg_O2 Time_i
Time_f
Time Temp
mg/g/d
(days) (°C)
1
12.8 10.58
8.33
2.25 12.7
28.58
6:58
9:43
0.11 12.1
4.06
2
12.2 10.15
8.03
2.12 12.7
26.92
9:48
12:37
0.12 12.3
3.74
3
12.2
10.4
7.59
2.81 12.7
35.69
12:42
17:00
0.18 12.2
3.24
4
10.3 10.48
8.6
1.88 13.2
24.82
7:01
9:45
0.11 12.1
4.20
5
10.3 10.16
8.19
1.97 13.2
26.00
9:50
12:39
0.12 12.3
4.27
6
10.3 10.51
7.98
2.53 13.2
33.40
12:44
17:02
0.18 12.2
3.59
Respiration (R)
Specific Respiration (mg/g/d)
Variability with temperature
Variability with weight
Temperature
Weight (°C)
(g)
Example Raw Lake Trout Data
(specific rates and temperature)
Example Raw Lake Trout Data
(specific rates and fish size)
Application (fish physiology temperature)
1.) If fish respiration rate increase with
temperature what implications would this have
for growth rates?????
-e.g. higher rates of consumption needed
to achieve growth, fish management
Weight Gain
Weight Loss
-
+
Scope for Growth
Application (fish physiology - size)
1.) In general specific rates are higher for
smaller fish relative to their size than larger fish
at a given temperature
- smaller fish are undergoing higher rates of
growth, metabolism, etc. – where maximum
growth occurs
Hypothetical questions/aquaculture
• 1.) Determine the amount of oxygen to be
consumed in a day using calculated specific
respiration rates………
– e.g. at 60°C specific respiration rate for a 10 g fish
= 4mgO2/g/day
– How many milligrams of oxygen would 25 (10 g)
fish require in a day?
Hypothetical questions/aquaculture
• 2.) Determine the total amount of dissolved oxygen
available for fish usage…….(DO in tank is 9 mg/L,
threshold is 5 mg/L)
– Part A.) How much dissolved oxygen is available in
a 50 gallon tank (189.3 L) for a 4 mg/L drop in DO?
• 757.2 mg O2
Hypothetical questions/aquaculture
• Question 2, part B
– How many 10 gram fish will this support for 1 day
at 4 mg/g/day respiration rate (without aeration)?
• 1 – 10 g fish = 40mg O2/day
• 757.2mgO2/40mgO2 / day=18.9 or 18 fish for 1 day
PSTA Science and Technology
Standards
• Inquiry and Design-3.2.7,3.2.10,3.2.12; Parts A
and B
• Biological Sciences- 3.3.12; Part B
• Earth Sciences – 3.5.7,10,12; Part D
Let’s check on our experiment
and collect data!
Modifications of experiments
•
•
•
•
•
Temperature
Size
Individual vs. Group experiments
Duration of experiments
Multiple measurements on fish
Questions???