CFP Aquatic Species Monitoring 3 — Questions and Answers
Question 1: Which otolith preparation technique allows fisheries biologists to determine daily age increments in larval fish?
- Whole otolith transmitted light microscopy after polishing to the primordium (Correct answer)
- Sectioning through the dorsal spine
- Scale aging using the annulus count
- Fin ray cross-section analysis
Correct answer: Whole otolith transmitted light microscopy after polishing to the primordium
Daily growth increments in larval otoliths are visible under transmitted light after grinding the otolith to expose the inner primordium layer.
Question 2: In a multi-pass depletion electrofishing survey, population size is estimated by observing that catch decreases with each pass. Which statistical model is used to estimate the original population?
- Zippin removal model (Correct answer)
- Schaefer surplus production model
- Von Bertalanffy growth model
- Ricker stock-recruitment model
Correct answer: Zippin removal model
The Zippin removal model uses the declining catches across successive passes to estimate population size and capture probability.
Question 3: What is the primary advantage of using eDNA (environmental DNA) sampling over traditional netting for detecting rare or cryptic aquatic species?
- Higher detection sensitivity with less physical disturbance to the habitat (Correct answer)
- Allows precise population size estimation
- Provides age and growth data
- Lower laboratory processing cost than electrofishing
Correct answer: Higher detection sensitivity with less physical disturbance to the habitat
eDNA methods can detect species presence from shed cells and mucus in water with high sensitivity without disturbing the organism or habitat.
Question 4: A fisheries biologist calculates a relative stock density (RSD) of 15 for a largemouth bass population. What does this low value indicate?
- Few fish have reached quality size relative to the number of stock-size fish (Correct answer)
- The population has high trophy-sized fish abundance
- Recruitment is severely limited
- The population is at carrying capacity
Correct answer: Few fish have reached quality size relative to the number of stock-size fish
A low RSD indicates that a small proportion of stock-size fish have grown to quality size, suggesting potential stunting or high predation on larger fish.
Question 5: When using fyke nets to monitor fish assemblages in wetlands, which factor most strongly biases catch composition?
- Water temperature affecting fish activity and movement (Correct answer)
- Net mesh size relative to fish length
- Time of day of net deployment
- Distance from the shoreline
Correct answer: Water temperature affecting fish activity and movement
Water temperature drives fish activity levels and migration behavior, strongly influencing which species and size classes are captured in passive gear like fyke nets.
Question 6: A biologist is monitoring a mussel bed and needs to determine population density. Which method provides the most accurate density estimate for sessile bivalves?
- Stratified random quadrat sampling (Correct answer)
- Mark-recapture with PIT tags
- Hydroacoustic side-scan sonar only
- Electrofishing transects
Correct answer: Stratified random quadrat sampling
Stratified random quadrat sampling accounts for habitat heterogeneity and provides unbiased density estimates for sedentary organisms like freshwater mussels.
Question 7: Which metric best describes the temporal stability of a fish community at a monitoring site across multiple years?
- Bray-Curtis similarity index calculated between annual samples (Correct answer)
- Annual CPUE for the dominant species
- Mean total length of harvested fish
- Fulton's K averaged across species
Correct answer: Bray-Curtis similarity index calculated between annual samples
The Bray-Curtis similarity index quantifies compositional overlap between two community samples, enabling assessment of year-to-year community change.
CFP Aquatic Species Monitoring 3
Which otolith preparation technique allows fisheries biologists to determine daily age increments in larval fish?