Stock Exploitation Status

All fish within a given species are typically capable of reproducing successfully, although their range of distribution is generally broad enough to restrict reproduction to small sub-populations. Over time, these sub-populations may develop small differences in size, shape or behavior that are genetically-based or which result from local fishing pressure. Separate management plans are typically created for each sub-population.  Managed sub-populations are referred to as 'stocks'.

The Food and Agriculture Organization of the United Nations (FAO) tracks approximately 600 stocks of the species that comprise global fisheries catch. Under intense exploitation, most fisheries experience the following sequence: undeveloped, developing, fully exploited, overexploited, collapsed and (if appropriate management measures are taken) rebuilding. FAO developed the following qualitative definitions to describe progressive stock exploitation stages:

•      Underexploited  
        Undeveloped or new fishery
        Believed to have a significant potential for expansion in total production

•      Moderately exploited
        Exploited with a low level of fishing effort
        Believed to have some limited potential for expansion in total production

•      Fully exploited
        The fishery is operating at or close to an optimal yield level, with no expected
        room for further expansion

•      Overexploited
        The fishery is being exploited at above a level that is believed to be sustainable in 
        the long term, with no potential room for further expansion and a higher risk of 
        stock depletion/collapse

•      Depleted
        Catches are well below historical levels, irrespective of the amount of 
        fishing effort exerted

•      Recovering
        Catches are again increasing after having been depleted

Stock Status Infographic
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Which Goals Does This Affect?


How Was It Measured?

Stock exploitation measures the annual status of individual stocks using the relationship between the current level of catch and the peak catch for that stock. Sea Around Us provided status data that combined the Food and Agriculture Organization of the United Nations (FAO) categories of ‘underexploited’ and ‘moderately exploited’ into one overall ‘developing’ category, thereby defining five levels of exploitation status: Developing, Exploited, Overexploited, Collapsed, and Rebuilding.

Regional scores were calculated as the average score of all stocks fished in a country based upon these five categories and using the following sustainability coefficients for each: Developing stock (1.0), Fully Exploited (0.5); Overexploited (0.5); Rebuilding (0.25); Collapsed (0.0).

Countries with fewer than three stocks assessed were treated as data deficient and assigned a default weight 0.5.

What Are The Impacts?

87% of the World's Wild-Caught Fisheries Are Fully Exploited, Overexploited or Depleted
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ECOLOGICAL IMPACT
Overfishing has caused significant decreases in catches for many of the world’s fisheries, negatively impacting ecosystem health and the sustainability of stocks.
HUMAN HEALTH IMPACT
Human food supplies have been reduced due to overfishing and the resultant decline in catches for many of the world’s fisheries.

A product of the fishing industry, fish oil is an important source of omega-3 fatty acids, which can provide nutritional benefits to humans. Over-exploited fisheries may be unable to sustainably supply increased amounts of fish oils and production levels have decreased in recent years.

In 2009, total fish oil production by the five main exporting countries (Peru, Chile, Iceland, Norway, and Denmark) was 530,000 tonnes, 100,000 tonnes less than in 2008 (FAO 2010).
ECONOMIC IMPACT
Overfishing and decreased overall catches in fisheries threaten the social and economic sustainability of fishing communities worldwide.

Properly managed sustainable fisheries could provide global net economic benefits of $50 billion more each year (World Bank and Food and Agriculture Organization 2008).


References




PHOTO(S): © Keith A. Ellenbogen
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