CFP CFP Fish Population Dynamics & Stock Assessment 1 — Questions and Answers
Question 1: Which metric is used in stock assessment to describe the maximum sustainable yield (MSY) of a fish population?
- The largest single-year catch ever recorded
- The highest yield that can be taken from a stock indefinitely under existing conditions (Correct answer)
- The average annual catch over the past decade
- The total biomass of all age classes combined
Correct answer: The highest yield that can be taken from a stock indefinitely under existing conditions
MSY is defined as the highest yield that can be sustainably taken from a stock under existing environmental conditions.
Question 2: In a catch-per-unit-effort (CPUE) index, what does a declining CPUE typically indicate?
- Improved fishing gear efficiency
- A decrease in fish abundance or population density (Correct answer)
- An increase in fishing effort
- Better data collection methods
Correct answer: A decrease in fish abundance or population density
A declining CPUE generally signals that fish abundance is decreasing relative to the fishing effort applied.
Question 3: What is the purpose of a virtual population analysis (VPA) in fisheries science?
- Simulate fish behavior in virtual environments
- Reconstruct historical population size and fishing mortality from catch-at-age data (Correct answer)
- Model fish migration routes using GPS tracking
- Estimate habitat suitability scores for spawning areas
Correct answer: Reconstruct historical population size and fishing mortality from catch-at-age data
VPA uses age-structured catch data to back-calculate the historical abundance and fishing mortality of a stock.
Question 4: Which age-determination method is most commonly used for freshwater fishes in the US?
- Vertebrae cross-sections
- Dorsal fin spine annuli
- Otolith thin-sections and whole otoliths
- Scale annuli (Correct answer)
Correct answer: Scale annuli
Scale annuli are the most widely used aging method for many US freshwater species because scales are easy to collect non-lethally.
Question 5: The Beverton-Holt recruitment model describes what relationship?
- The link between water temperature and fish growth rates
- The relationship between spawning stock biomass and subsequent recruitment (Correct answer)
- The correlation between habitat quality and species diversity
- The effect of fishing mortality on age structure
Correct answer: The relationship between spawning stock biomass and subsequent recruitment
The Beverton-Holt model is a stock-recruitment function that relates the number of spawners to the number of recruits produced.
Question 6: What does the term 'recruitment overfishing' mean in stock assessment?
- Harvesting fish before they reach minimum legal size
- Reducing the spawning stock so severely that recruitment is impaired (Correct answer)
- Exceeding the quota set for a given fishing season
- Targeting juvenile fish during spawning aggregations
Correct answer: Reducing the spawning stock so severely that recruitment is impaired
Recruitment overfishing occurs when the spawning population is reduced to a level where it can no longer produce adequate numbers of juveniles to sustain the stock.
CFP CFP Fish Population Dynamics & Stock Assessment 1
Which metric is used in stock assessment to describe the maximum sustainable yield (MSY) of a fish population?