overfishing
science Overfishing is a situation where one or more fish stocks are reduced below predefined levels of acceptance by fishing activities. More precise definitions are provided in biology and bioeconomics. Biological overfishing occurs when fishing mortality has reached a level where the stock biomass has negative marginal growth (slowing down biomass growth), as indicated by the red area in the figure. Economic or bioeconomic overfishing in addition to the biological dynamics takes into consideration the cost of fishing and defines overfishing as a situation of negative marginal growth of resource rent. A more dynamic definition may also include a relevant discount rate and present value of flow of resource rent over all future catches.
Ultimately overfishing may lead to depletion in cases of subsidised fishing, low biological growth rates and critical low biomass levels (e.g. by critical depensation growth properties).
The ability for nature to restore the fisheries is also dependent on whether the ecosystems are still in a state to allow fish numbers to build again. Dramatic changes in species composition may establish other equilibrium energy flows which involve other species compositions than before (ecosystem shift).
A major international scientific study released in November 2006 in the journal Science found that about one-third of all fishing stocks worldwide have collapsed (with a collapse being defined as a decline to less than 10% of their maximum observed abundance), and that if current trends continue all fish stocks worldwide will collapse within fifty years.[1]
The FAO State of World Fisheries and Aquaculture 2004 report estimates that in 2003, of the main fish stocks or groups of resources for which assessment information is available, "approximately one-quarter were overexploited, depleted or recovering from depletion (16%, 7% and 1% respectively) and needed rebuilding."[2]
The threat of overfishing is not limited to the target species only. As
Ultimately overfishing may lead to depletion in cases of subsidised fishing, low biological growth rates and critical low biomass levels (e.g. by critical depensation growth properties).
The ability for nature to restore the fisheries is also dependent on whether the ecosystems are still in a state to allow fish numbers to build again. Dramatic changes in species composition may establish other equilibrium energy flows which involve other species compositions than before (ecosystem shift).
A major international scientific study released in November 2006 in the journal Science found that about one-third of all fishing stocks worldwide have collapsed (with a collapse being defined as a decline to less than 10% of their maximum observed abundance), and that if current trends continue all fish stocks worldwide will collapse within fifty years.[1]
The FAO State of World Fisheries and Aquaculture 2004 report estimates that in 2003, of the main fish stocks or groups of resources for which assessment information is available, "approximately one-quarter were overexploited, depleted or recovering from depletion (16%, 7% and 1% respectively) and needed rebuilding."[2]
The threat of overfishing is not limited to the target species only. As