Final answer:
Profits from fishing can stay the same with diminishing fish stock due to increased scarcity and prices, but this is unsustainable, justifying regulation to maintain sustainability.
Step-by-step explanation:
According to the 'persistent tendency towards depletion theory,' profits made from fishing can stay the same while the fish stock is steadily diminished because even as the number of fish decreases, the remaining fish increase in scarcity and thus, in value, leading to higher prices. This can temporarily keep profits stable, despite the declining stock. However, this is an unsustainable practice as continued depletion will eventually collapse the fishery and cause long-term economic and ecological harm.
Therefore, regulation by outsiders, such as scientists and policymakers, is justified to maintain sustainability and prevent the overexploitation of the fish stock, which aligns with option A of the question which states profits remain the same due to increased prices, and outsiders regulate to maintain sustainability.