Overfishing is the removal of a species of fish from a body of water at a rate that the species cannot replenish, resulting in those species becoming underpopulated in that area.
In a Food and Agriculture Organization estimates that one-third of world fish stocks were overfished by 2015. Overfishing can occur in water bodies of any sizes, such as ponds, rivers, lakes or oceans, and can result in resource depletion, reduced biological growth rates and low biomass levels. Sustained overfishing can lead to critical depensation, where the fish population is no longer able to sustain itself. Some forms of overfishing, such as the overfishing of sharks, has led to the upset of entire marine ecosystems.
The ability of a fishery to recover from overfishing depends on whether the ecosystem’s conditions are suitable for the recovery. Dramatic changes in species composition can result in an ecosystem shift, where other equilibrium energy flows involve species compositions different from those that had been present before the depletion of the original fish stock. For example, once trout have been overfished, carp might take over in a way that makes it impossible for the trout to re-establish a breeding population. Scientists estimate that each year 100 million sharks are removed from our oceans, and much of this haul is illegal, unreported and unregulated. The fishing pressure on sharks, combined with their slow rate of reproduction, means that they are being overfished.
When fishermen catch fish, there are inevitably fewer fish left in the sea. If it weren’t for fishes’ ability to reproduce relatively quickly, fishermen would simply ‘mine down’ the resource and there would be nothing left. But fishing has been sustained for many millennia because fish can reproduce and recover their numbers. This source of potentially endless protein is what makes our fish stocks one of our most valuable renewable resources.
The solution would seem simple:
Reduce the number of fish we catch. But a major obstacle to conservation efforts is our limited understanding. We simply don’t properly understand behavior, breeding habits or migration patterns of most species. For some species, we don’t even know how many of them there are! Without this basic knowledge, we can’t accurately calculate fishing limits and develop other effective conservation measures to conserve them.
