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Marine Trophic Index

Key indicator facts

Indicator type

Pressure

Applicable for national use

Yes

Indicator classification

Potential for future use at global and regional levels

Indicator type

Pressure

Applicable for national use

Yes

Indicator classification

Potential for future use at global and regional levels

Last update

2008

Coverage

Global

Availability

Freely available

Partners

Seaaroundus

Sea Around Us

Contact point

Indicator description

Fish currently supply the greatest percentage of the world’s protein consumed by humans. However, most of the world’s fisheries are being fished at levels above their maximum sustainable yield and many regions are severely overfished. The Marine Trophic Index measures the mean trophic level for all Large Marine Ecosystems and hence indicates the extent of ‘fishing down the food webs’. This provides a measure of whether fish stocks, especially of large bodied fish, are being overexploited and fisheries are being sustainably managed.

Related Aichi Targets

Primary target

6

Target 6:

By 2020 all fish and invertebrate stocks and aquatic plants are managed and harvested sustainably, legally and applying ecosystem based approaches, so that overfishing is avoided, recovery plans and measures are in place for all depleted species, fisheries have no significant adverse impacts on threatened species and vulnerable ecosystems and the impacts of fisheries on stocks, species and ecosystems are within safe ecological limits.

Primary target

6

Target 6:

By 2020 all fish and invertebrate stocks and aquatic plants are managed and harvested sustainably, legally and applying ecosystem based approaches, so that overfishing is avoided, recovery plans and measures are in place for all depleted species, fisheries have no significant adverse impacts on threatened species and vulnerable ecosystems and the impacts of fisheries on stocks, species and ecosystems are within safe ecological limits.

6

Related SDGs

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GOAL 2 - End hunger, achieve food security and improved nutrition and promote sustainable agriculture.

Target 2.4| Relevant indicator

By 2030, ensure sustainable food production systems and implement resilient agricultural practices that increase productivity and production, that help maintain ecosystems, that strengthen capacity for adaptation to climate change, extreme weather, drought, flooding and other disasters and that progressively improve land and soil quality.

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GOAL 12 - Ensure sustainable consumption and production patterns.

Target 12.2| Relevant indicator

By 2030, achieve the sustainable management and efficient use of natural resources.

Target 12.8| Relevant indicator

By 2030, ensure that people everywhere have the relevant information and awareness for sustainable development and lifestyles in harmony with nature.

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GOAL 14 - Conserve and sustainably use the oceans, seas and marine resources for sustainable development.

Target 14.4| Relevant indicator

By 2020, effectively regulate harvesting and end overfishing, illegal, unreported and unregulated fishing and destructive fishing practices and implement science-based management plans, in order to restore fish stocks in the shortest time feasible, at least to levels that can produce maximum sustainable yield as determined by their biological characteristics.

Target 14.7| Relevant indicator

By 2030, increase the economic benefits to Small Island developing States and least developed countries from the sustainable use of marine resources, including through sustainable management of fisheries, aquaculture and tourism.

Target 14.c| Relevant indicator

Enhance the conservation and sustainable use of oceans and their resources by implementing international law as reflected in UNCLOS, which provides the legal framework for the conservation and sustainable use of oceans and their resources, as recalled in paragraph 158 of The Future We Want.

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GOAL 2 - End hunger, achieve food security and improved nutrition and promote sustainable agriculture.

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GOAL 12 - Ensure sustainable consumption and production patterns.

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GOAL 14 - Conserve and sustainably use the oceans, seas and marine resources for sustainable development.

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Other related MEAs and processes

Cites high resolution

CITES

Target 1.4| Relevant indicator

The Appendices correctly reflect the conservation needs of species.

Cms logo blue4c

CMS

Target 5| Relevant indicator

Governments, key sectors and stakeholders at all levels have taken steps to achieve or have implemented plans for sustainable production and consumption, keeping the impacts of natural resource use on migratory species well within safe ecological limits to promote the favourable conservation status of migratory species and maintain the quality, integrity, resilience, and connectivity of their habitats and migratory routes.

Target 6| Relevant indicator

Fisheries and hunting have no significant direct or indirect adverse impacts on migratory species, their habitats or their migration routes, and impacts of fisheries and hunting are within safe ecological limits.

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IPBES Global Assessment Chapters

Chapter 2| Official indicator

Status and trends; indirect and direct drivers of change

Chapter 3| Official indicator

Progress towards meeting major international objectives related to biodiversity and ecosystem services

Indicator icon

IPBES Regional Assessment Chapters

Chapter 3| Relevant indicator

Status, trends and future dynamics of biodiversity and ecosystems underpinning nature’s benefits to people

Cites high resolution

CITES

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CMS

Indicator icon

IPBES Global Assessment Chapters

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IPBES Regional Assessment Chapters

Cites high resolution
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Indicator icon
Indicator icon

Themes

Marine

Marine & freshwater habitats

View related indicators >
Bip sustainable

Sustainable use of natural resources and land

View related indicators >
Marine
Bip species
Bip sustainable

Partners

Seaaroundus

Key indicator facts

Indicator type

Pressure

Applicable for national use

Yes

Indicator classification

Potential for future use at global and regional levels

Indicator type

Pressure

Applicable for national use

Yes

Indicator classification

Potential for future use at global and regional levels

Last update

2008

Coverage

Global

Availability

Freely available

Indicator description

Fish currently supply the greatest percentage of the world’s protein consumed by humans. However, most of the world’s fisheries are being fished at levels above their maximum sustainable yield and many regions are severely overfished. The Marine Trophic Index measures the mean trophic level for all Large Marine Ecosystems and hence indicates the extent of ‘fishing down the food webs’. This provides a measure of whether fish stocks, especially of large bodied fish, are being overexploited and fisheries are being sustainably managed.

Contact point

Graphs / Diagrams

Current storyline

Fish currently supply the greatest percentage of the world’s protein consumed by humans. However, most of the world’s fisheries are being fished at levels above their maximum sustainable yield and many regions are severely overfished. In the late 1990s, it was demonstrated that the mean trophic level of fisheries is declining, i.e. that global fisheries catches increasingly consist of smaller fish and invertebrates lower in the food web. This process, now known as ‘fishing down marine food webs’ (see www.fishingdown.org) has become a major concern, as it means that fish stocks especially of large bodied fish are being overexploited and fisheries are not being sustainably managed. This severely threatens marine biodiversity.

The Marine Trophic Index (MTI) has been developed by the Sea Around Us (www.seaaroundus.org) at the UBC Global Fisheries Cluster (http://www.global-fc.ubc.ca/), and was established to investigate the impacts of fisheries on the world’s marine ecosystems. The MTI can be used to describe the complex interactions between fisheries and marine ecosystems and communicate a measure of species replacement indices by fisheries. The concept and underlying methods to estimate the MTI have been well–tested and have undergone substantial peer-review using existing information. The MTI, which tracks the mean trophic level of fishery catches from an ecosystem, adequately tracks changes in mean trophic level of an ensemble of exploited species in response to fishing pressure.

The Marine Trophic Index (MTI) has been developed by the Sea Around Us (www.seaaroundus.org) at the UBC Global Fisheries Cluster (http://www.global-fc.ubc.ca/), and was established to investigate the impacts of fisheries on the world’s marine ecosystems. The MTI can be used to describe the complex interactions between fisheries and marine ecosystems and communicate a measure of species replacement indices by fisheries. The concept and underlying methods to estimate the MTI have been well –tested and have undergone substantial peer-review using existing information. The MTI, which tracks the mean trophic level of fishery catches from an ecosystem, adequately tracks changes in mean trophic level of an ensemble of exploited species in response to fishing pressure. However, one of the disadvantages of this indicator is that declines in trophic level can be masked by geographic expansion and/or the development of offshore fisheries (see Swartz et al. 2010. PLoS ONE 5(12): e15143), where higher trophic levels of newly accessed resources can overwhelm fishing-down effects closer inshore. Thus, the MTI should not be used without accounting for changes in the spatial and bathymetric reach of the fishing fleet, and the Sea Around Us presents a re-developed index that accounts for the potential geographic expansion of fisheries over time, called the Region-based MTI (RMTI, see Kleisner et al. 2014. Marine Ecology Progress Series 512:185-199). To calculate the RMTI, the potential catch that can be obtained given the observed trophic structure of the actual catch is used to assess the fisheries in an initial (usually coastal) region. Actual catch exceeding potential catch indicates exploitation of a new fishing region. The MTI of the new region can then be calculated and subsequent regions are determined in a sequential manner. This method improves upon the use of the Fishing-in-Balance (FiB) index in conjunction with the original MTI calculated over the whole time series because assumptions of fleet and stock stationarity over the entire time series and geographic area are removed. As a default, the Sea Around Us presents the RMTI as well as the original MTI/FiB indices in parallel.

The RMTI and MTI/FiB is calculated from reconstructed catch composition data assembled by the Sea Around Us as part of their global coverage of reconstructed catch data. Reconstructed catch data consist of the combination of officially reported data (as reported by countries to FAO) plus comprehensive time series estimates of all unreported catches and unreported discards. All data are global, cover 1950 to the most recent year of data, taxonomically disaggregated and assigned to four fisheries sectors (industrial, artisanal, subsistence and recreational). Data spatially allocated to EEZs, LMEs or other relevant spatial ecosystem components. The concept and approach is now widely accepted and well published.

The RMTI and MTI/FiB has been calculated for the Exclusive Economic Zone (EEZ) of each country, for all Large Marine Ecosystems (LME), for High Seas areas as well as globally from 1950 to the most recent year of data processed by the Sea Around Us. The data for all EEZs and LMEs and other spatial components can be viewed and downloaded from the Sea Around Us. Information on how the RMTI and MTI/FiB is calculated can be viewed via the Marine Trophic Index pages at http://www.seaaroundus.org/data/#/marine-trophic-index.

The trend in mean trophic level for all LMEs combined indicates a decline in the MTI from a peak in the 1950s to a low in the mid 1980s. The decline represents a global decrease in the abundance of high tropic level species, resulting in the phenomenon of ‘fishing down marine food webs’ (www.fishingdown.org), in which fisheries catches increasingly consist of smaller fish and invertebrates lower in the food web.

From the mid 1980s there is a trend reversal and the global MTI increases. This increase does not necessarily represent improvements in the global sustainability of fisheries and in turn an increase in the abundance of higher trophic level species. In fact, data from the complementary Fishing-in-Balance (FiB) index (see www.seaaroundus.org), a measure of the ‘balance’ between catches and tropic level indicates that this increase is the result of offshore expansion of the fisheries into deeper and more pelagic waters where there were still healthier stocks of large predatory fish such as tuna, swordfish, and marlins. These stocks have since also declined over time.

The global index excludes data for Peruvian anchoveta. The very localized fishery for Peruvian anchoveta, a low trophic level species, is the largest single-species fishery in the world, and it exhibits extreme fluctuations in landings which would mask the comparatively more subtle patterns in trophic level changes by the rest of the world’s fisheries. RMTI as presented here is impacted by geographic expansion of fisheries within an area examined (here for the entire world oceans).

A decrease in one or more Region-based Marine Trophic Index lines (‘region’ split) represents a decline in the abundance and diversity of fish species high in the food chain, such as cod. This process also termed ‘fishing down marine food webs’, now independently documented in many regions and ecosystems (www.fishingdown.org), means that fish stocks are being overexploited and fisheries are not being sustainably managed in many places. As a result the biodiversity of these resources will be threatened. The loss of top predators and the reduction of the trophic structure in oceans will have consequences for ecosystem stability and function, threatening biodiversity more broadly. Active and effort-restrictive management in more recent years for some species in some countries may be constraining these patterns.

Alternatively to using the RMTI, the original MTI can be used, but the MTI should always be interpreted in conjunction with a simultaneous interpretation of the FiB index (Fishing-in-Balance Index), both of which continue to be available at www.seaaroundus.org.

A first examination of the original MTI (bottom left graph) suggests that, after an initial period of stability in the 1950s and early 1960s, the global MTI declined strongly to the mid-1980s, but increased again in the 1990s and 2000s, ending at trophic levels nearly identical to the start of the time series. However, examination of the FiB co-index (Fishing-in-Balance, bottom right graph) suggests that continuous spatial expansion occurred in global fisheries (as FiB >0), as also described in Swartz et al. (2010. PLoS ONE 5(12): e15143). Thus, the application of the improved RMTI (top graph) illustrates that at least three major spatial expansions could be segregated, with at least the two earlier ‘regional’ expansions (one from 1950 to end of time series, the second starting in the late 1950s) showing continuous trophic level declines (the two bottom RMTI lines). The most recent ‘regional’ split (top line in RMTI) illustrates a currently more or less stable trophic level and most likely represents the global tuna and billfish fisheries (trophic levels >4).

For a list and references to a growing number of local and regional case studies, see www.fishingdown.org .

Data and methodology

Coverage: Global/national.

Scale: The RMTI indicator can be applied at different scales from global to subnational (e.g. portion of the EEZ of a country). For countries such as Malaysia and Indonesia with EEZs in different basins, the RMTI can be calculated for those sub-national areas. The data is readily available at these different scales via the Sea Around Us website. Note that the data being used for RMTI are reconstructed catches (i.e., reported catches plus estimated unreported catches and discards) in spatially defined areas from all countries known to fish or deemed to fish in these areas. In simple terms, the RMTI is not based on catches by a country but rather is based on catches in the waters of a country or area of interest.

Time series available: 1950-2010.

Next planned update: 2016.

Possible disaggregations: Regional level, national level. The data, although catch based, can be disaggregated into different taxonomic classifications from very broad groupings (e.g. Fish, crustaceans and molluscs) to habitat based fish (demersal, bathydemersal, etc.) to species and genus. It is possible to report on a combination of thematic and spatial themes.

Metadata: The RMTI and MTI/FiB is calculated from reconstructed catch composition data assembled by the Sea Around Us as part of their global coverage of reconstructed catch data. Reconstructed catch data consist of the combination of officially reported data (as reported by countries to FAO) plus comprehensive time series estimates of all unreported catches and unreported discards. All data are global, cover 1950 to the most recent year of data, taxonomically disaggregated and assigned to four fisheries sectors (industrial, artisanal, subsistence and recreational). Data spatially allocated to EEZs, LMEs or other relevant spatial ecosystem components.

Methodology: To calculate the RMTI, the potential catch that can be obtained given the observed trophic structure of the actual catch is used to assess the fisheries in an initial (usually coastal) region. Actual catch exceeding potential catch indicates exploitation of a new fishing region. The MTI of the new region can then be calculated and subsequent regions are determined in a sequential manner. This method improves upon the use of the Fishing-in-Balance (FiB) index in conjunction with the original MTI calculated over the whole time series because assumptions of fleet and stock stationarity over the entire time series and geographic area are removed. As a default, the Sea Around Us presents the RMTI as well as the original MTI/FiB indices in parallel.

National use of indicator

The RMTI (as well as original MTI/FiB) is available for the EEZs (or even distinct subsets of EEZs) of every coastal country in the world and for all currently defined LMEs. Furthermore, the RMTI indicator can be readily calculated and applied at different scales from global to national. For countries such as Malaysia and Indonesia, with EEZs in different basins, the MTI can be calculated for sub-national areas.

All data, including country level RMTIs are available from the Sea Around Us website, and the R-code for the RMTI is freely available. For advice about the interpretation of RMTIs see the original literature available at the Sea Around Us, or contact the Sea Around Us via the ‘feedback’ link on the project website.

Further resources

Key indicator facts

Indicator type

Pressure

Applicable for national use

Yes

Indicator classification

Potential for future use at global and regional levels

Indicator type

Pressure

Applicable for national use

Yes

Indicator classification

Potential for future use at global and regional levels

Last update

2008

Coverage

Global

Availability

Freely available

Partners

Seaaroundus

Sea Around Us

Contact point