Question

As per the analytical models of fish stock assessment, presence of too many old fish in the stock is an indicative of :

• A. Growth overfishing
• B. Recruitment overfishing
• C. Underfishing
• D. Eumetric fishing

Hint:

Remember: Low exploitation (Underfishing) allows fish to grow old and reach maximum age, while High exploitation (Overfishing) depletes older cohorts, leaving only young cohorts.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Fish stock assessment models analyze the age and size structure of fish populations to evaluate the status of exploitation of a fishery.
The proportions of young, mature, and old fish in a stock are directly influenced by the fishing mortality rate (\(F\)).

Step 2: Detailed Explanation:
Let us analyze the ecological indications of different catch composition scenarios:
- Underfishing (C): If the fishing effort is extremely low, the rate of fishing mortality is negligible. This allows a large proportion of individual fish to escape harvest, survive for many years, and reach their maximum potential size and age. Consequently, the stock will contain a high proportion of "too many old fish."
Let us compare this with the other options:
1. Growth overfishing (A): Occurs when fish are harvested at an average size that is smaller than the size that would produce the maximum yield per recruit. It is characterized by an abundance of small, young fish and a lack of larger fish.
2. Recruitment overfishing (B): Occurs when the spawning biomass is depleted by fishing to a level where it can no longer produce enough offspring to sustain the stock.
3. Eumetric fishing (D): Represents the ideal situation where the mesh size and fishing effort are balanced to harvest fish at the optimum age/size, maximizing long-term yield.

Step 4: Final Answer:
Therefore, the presence of too many old fish in the stock is an indicative of Underfishing.