Final answer:
When a fish stock falls below the minimum viable population level, its growth rate is likely negative, potentially leading to extinction if mitigating actions like decreased fishing are not taken. This reveals the delicate balance required for maintaining healthy marine ecosystems and sustainable fishing practices.
Step-by-step explanation:
If a fish stock falls below the minimum viable population level, then the growth rate of that fish stock is likely to become negative, meaning the population will continue to decrease. This can occur due to various factors such as overfishing which has historically led to the collapse of species like the cod. In such situations, the populations become so small that they might not recover. Moreover, as stated by Pimm et al. (1988), those populations that fluctuate greatly from year to year are more likely to hit these critically low numbers.
Furthermore, ecological principles suggest that when energy flow into an ecosystem, such as a pond, decreases, the population sizes of all organisms will usually decrease as a response. Similarly, if negative factors that reduce the populations continue without being mitigated, the taxa can be pushed towards extinction. Decreased fishing, on the other hand, can be expected to lead to rebounds in fish populations and to more healthy marine ecosystems.
It is important to note that while fishery extinction does not always mean biological extinction, it can still be extremely harmful to fish species and their ecosystems, and in some cases, true extinction is indeed a risk.