Question

Virtual population of fish denotes

• A. Virgin population
• B. Absolute population
• C. Maximum sustainable population
• D. Exploited population

Hint:

Fisheries Stock Concepts:
Virtual Population Analysis (VPA) = Back-calculation of EXPLOITED POPULATION from Catch-at-age data.
Virgin Population ($B_0$) = Unfished pristine biomass.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Fisheries stock assessment modeling: Virtual Population Analysis (VPA Cohort Analysis) reconstructs the historical exploited stock cohort size backwards from commercial catch-at-age statistics.
Key Formula or Approach:
\[ N_t = N_{t+1} e^M + C_t e^{M/2} \quad [\text{Reconstruction of Exploited Cohort Numbers}] \]

Step 2: Detailed Explanation:
In fisheries stock assessment (Fry 1949, Gulland 1965):
- Virtual Population (VPA Cohort Analysis): Refers to the calculated historical size and demographic structure of the Exploited Fish Population that must have been present in the sea to account for the observed commercial catch-at-age time series data.
- By back-calculating using catch data ($C_t$) and natural mortality ($M$), it reconstructs fishing mortality ($F$) and historical cohort biomass of the harvested fishery stock.

Step 3: Final Answer:
Thus, virtual population of fish denotes the Exploited population, matching option (D).