Question

What is the annual fishing mortality rate, if the fishing effort is 8000 vessels and catchability coefficient is \(5 \times 10^{-4}\) per vessel per year ?

• A. 2.0
• B. 4.0
• C. 1.6
• D. 3.2

Hint:

To easily calculate this in your head, multiply the coefficient base by the effort base: \(5 \times 8 = 40\). Then balance the powers of ten: \(10^{-4} \times 10^{3} = 10^{-1}\). Thus, \(40 \times 10^{-1} = 4.0\).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
In fish stock assessment, fishing mortality (\(F\)) represents the rate at which fish are removed from a population due to harvesting.
It is directly proportional to the fishing effort (\(f\)) exerted by the fishing fleet and the catchability coefficient (\(q\)), which represents the efficiency of a single unit of effort.
Key Formula or Approach:
The relationship between fishing mortality, fishing effort, and the catchability coefficient is given by the formula:
\[ F = q \times f \]
where:
\( F \) = Fishing mortality rate (per year)
\( q \) = Catchability coefficient (per vessel per year)
\( f \) = Fishing effort (number of vessels)

Step 2: Detailed Explanation:
Let us substitute the given values into the formula:
Given:
- Fishing effort (\(f\)) = \(8000\text{ vessels}\)
- Catchability coefficient (\(q\)) = \(5 \times 10^{-4}\text{ per vessel per year}\)
Now, calculate the fishing mortality (\(F\)):
\[ F = (5 \times 10^{-4}) \times 8000 \]
\[ F = 5 \times 10^{-4} \times 8 \times 10^3 \]
\[ F = 40 \times 10^{-1} \]
\[ F = 4.0\text{ per year} \]
Therefore, the annual fishing mortality rate is 4.0.

Step 4: Final Answer:
The annual fishing mortality rate is 4.0, which corresponds to Option (B).