CFP Aquatic Species Monitoring 2 — Questions and Answers
Question 1: Which sampling gear is most appropriate for monitoring benthic macroinvertebrates in a riffle habitat?
- Surber sampler (Correct answer)
- Fyke net
- Gill net
- Trammel net
Correct answer: Surber sampler
Surber samplers enclose a defined area of stream bottom and collect drift, making them ideal for benthic macroinvertebrate sampling in riffles.
Question 2: In mark-recapture studies, the Lincoln-Petersen estimator assumes which of the following?
- Marked individuals mix randomly with the population (Correct answer)
- The population is closed to immigration and emigration only between sampling events
- All individuals have unequal probability of capture
- Marks are shed at a known rate
Correct answer: Marked individuals mix randomly with the population
A core assumption of the Lincoln-Petersen method is that marked fish mix randomly with unmarked fish before the recapture event.
Question 3: Passive integrated transponder (PIT) tags are preferred over anchor tags for long-term individual identification primarily because they:
- Are readable without recapturing the fish (Correct answer)
- Have no effect on fish growth or survival
- Are visible externally at distance
- Emit a continuous radio signal
Correct answer: Are readable without recapturing the fish
PIT tags can be detected by antennae at fish passages or with handheld readers without physically recapturing the animal.
Question 4: A crew electrofishing a warm-water stream sets the output to 60 Hz pulsed DC. What is the primary purpose of using pulsed rather than continuous DC?
- Reduce injury to fish while maintaining galvanotaxis (Correct answer)
- Increase the effective shocking radius
- Eliminate the need for a dip net
- Prevent equipment overheating
Correct answer: Reduce injury to fish while maintaining galvanotaxis
Pulsed DC induces galvanotaxis while reducing the duration of electrical exposure, lowering fish mortality and injury compared with continuous DC.
Question 5: Which index is most commonly used to assess fish community integrity relative to reference conditions in wadeable streams?
- Index of Biotic Integrity (IBI) (Correct answer)
- Shannon-Wiener diversity index
- Catch per unit effort (CPUE)
- Fulton's condition factor (K)
Correct answer: Index of Biotic Integrity (IBI)
The IBI scores multiple fish community metrics against reference-site benchmarks to evaluate overall biological condition.
Question 6: When conducting hydroacoustic surveys to estimate fish abundance, the target strength (TS) of an individual fish is primarily related to:
- Swim bladder size and fish length (Correct answer)
- Water temperature at depth
- Species coloration pattern
- Current velocity
Correct answer: Swim bladder size and fish length
Target strength is chiefly determined by the volume and angle of the swim bladder, which scales with fish length.
Question 7: A rotenone removal toxicant study is conducted to enumerate a lake fish population. After collection, which step is critical before interpreting density estimates?
- Correcting for incomplete fish recovery based on depth and habitat (Correct answer)
- Converting all weights to standard length
- Excluding species that were not stocked
- Applying a gear selectivity correction for gill nets
Correct answer: Correcting for incomplete fish recovery based on depth and habitat
Rotenone efficiency varies with water depth and habitat complexity, so estimates must account for fish that sink or were not retrieved.
CFP Aquatic Species Monitoring 2
Which sampling gear is most appropriate for monitoring benthic macroinvertebrates in a riffle habitat?