Measuring Fish Respiration A hands-on laboratory exercise Megan Kepler

Why study respiration? Energy in Energy out Consumption Egestion Excretion Metabolism 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

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 Steps for laboratory setup Water Bath Fernbach Flask 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 (g) DO_i (mg/L) DO_f (mg/L) ΔDO (mg/L) Vol (L) mg_O 2 Time_iTime_f Time (days) Temp (°C) mg/g/d :589: :4812: :4217: :019: :5012: :4417:

Respiration (R) Specific Respiration (mg/g/d) Temperature ( °C) Variability with temperature Variability with weight Weight (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 = 4mgO 2 /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? mg O 2

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 O 2 /day 757.2mgO 2 /40mgO 2 / day=18.9 or 18 fish for 1 day Hypothetical questions/aquaculture

PSTA Science and Technology Standards Inquiry and Design-3.2.7,3.2.10,3.2.12; Parts A and B Biological Sciences ; 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???