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catch data’ refers to information detailing how much fish is caught per country
on a global basis. ‘Catch’ refers to the total amount of whole fish captured. It
has a fundamental impact on fish populations and food webs because it represents removal of biomass
and individuals from an ecosystem. The
term ‘landings’ is used for the portion of catch that is brought to market on
shore. The weight of landings is frequently less than the weight of catch,
because guts are thrown overboard if fish are cleaned at sea; and some of a
vessel’s catch may be eaten by the crew, used for bait or discarded overboard
because it was undersized, spoiled or of the wrong species.
Trends in catch data can provide evidence of how well target populations are performing in response to fishing pressure. Currently, the only source of global marine catch data is the database collected annually by the United Nations Food and Agriculture Organization (FAO). FAO reports are based on information requested from all countries where fish is landed, and cover approximately 70 percent of commercially exploited stocks, as the remaining 30 percent have small landing numbers or the stocks or species groups caught are considered to be insignificant.
Although the majority of marine catch data do not provide reliable information on which particular species are being harvested, data based on landings or revenue, when accurately reported, can be a fair indicator of the status of global fisheries’ stocks. When adjusted for under or over-reporting, commercial landings were found to have stabilized (since the 1980s), and landing statistics have been revised to account for reporting corrections and inconsistencies. It is also important to note that official landings statistics selectively represent landings from the commercial fisheries sector and do not give an indication of everything that is being harvested from the ocean.
Catch data are also used to compile a “stock assessment”, which provides detailed information regarding the biological characteristics of a species or stock under fisheries’ management. This data can inform decisions regarding management regulations, fishery targets and future performance of selected stocks and species on a global basis.
Maximum sustainable yield (MSY) is a term used in fishery management to describe the highest average catch (by weight) that does not reduce a stock's abundance over time, taking into account the stock's reproductive and growth capacities under prevailing environmental conditions. MSY is typically determined for a single species, thereby ignoring effects on or from other species. It is a level of fishing that, if approached, should signal caution rather than increased fishing. Multispecies maximum sustainable yield (mMSY) is the highest average catch (by weight) of all target species in a region that could be caught over time without causing a decline in any single species.
How Was It Measured?
Fisheries catch data come from the United Nations Food and Agriculture Organization (FAO) global fisheries catch statistics, data from international and national fisheries agencies, and reconstructed catch datasets that have been spatialized to half-degree resolution in WGS84 geographic projection by the Sea Around Us Project and then aggregated to each reporting region. Data from 2006 were used for the current estimate because they are the most recent data spatialized by Sea Around Us. Cells spanning an EEZ boundary were allocated to each EEZ proportional to the area of the cell within the EEZ. When more than one EEZ fell within a single reporting unit, a weighted average was calculated based upon the relative area in the particular EEZ. Annual catch data for each species were smoothed using a 4-year moving window average and summed values across all species to get the total catch for each year during 1950-2006. Smoothed values were used instead of raw reported values to reduce potential bias from values that change due to changes in reporting rather than actual changes in landings.
Srinivasan et al. (2010) determined a log-linear relationship between the peak catch and the MSY for assessed stocks from the northeast US. The Ocean Health Index (OHI) used the same approach to determine mMSY from the peak catch for each commercially exploited species in the global catch database. Recognizing inherent uncertainty in estimating mMSY, including the fact that it does not account for interactions between species, the Index specifies a reference point (mMSYR), that is 25% below mMSY. Catches within +/-5% of mMSYR are deemed to be acceptable. Catches above or below that level are penalized, and catches more than twice mMSYR are given the lowest score.
What Are The Impacts?
Fish populations play vital roles in marine
ecosystem structure and function. Unsustainable fishing pressure can alter
entire ecosystems by changing food web dynamics.
HUMAN HEALTH IMPACT
worldwide depend upon fish as their primary protein source; overfishing can
threaten the availability of marine species for human consumption.
If overfishing did not exist, global fisheries could have prevented malnourishment for nearly 20 million people; and total catch in the waters of low-income food deficit nations might have been up to 17% greater than the tonnage actually landed there (Srinivasan et al. 2010).
Until about 1990, global fish landings and global human population increased at about the same rates, but after 1990 population has continued to increase and fish landings have leveled off or declined. Our population, currently at about 7 billion, will rise to 9 billion by 2042, an increase of 29%. Landings of wild-caught seafood will not increase at that rate, if at all (Global Education Project).
Fish is currently the most traded food
Overall fish stocks are below maximum sustainable yield, or are in decline, and catch per unit effort is decreasing.
Recent studies have shown that the global ceiling in marine fisheries production has been reached, and 40% of fisheries are actually decreasing in production (Garcia 2009; NRC 2006; Garcia & Rosenberg 2010).
Net losses to the global economy from unsustainable exploitation of living marine resources are calculated to substantially exceed $50 billion per year, equivalent to more than half the value of the global seafood trade (World Bank 2009).
Get More Information
Sea Around Us
The Sea Around Us project investigates the impact of fisheries on the marine ecosystems of the world, and offers mitigating solutions to a range of stakeholders. The project is a scientific collaboration between the University of British Columbia and the Pew Environment Group that began in July 1999. The Sea Around Us project conducts a catch reconstruction program, the results of which improve the accuracy of estimates of catch, stock exploitation status, and other key factors for fisheries management.
Fishery and catch related information is available at
FishSource, a fish stock database provided by the Sustainable Fisheries
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Food and Agriculture Organization of
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