Mean Trophic Index
PSBR model type
14.2.2 Mean Trophic Level (MTL) and Fishing in Balance Index (FiB) Quantitative target for 2020：MTL and FiB values are maintained at the current level, and data for constructing the index will be collected to compile Taiwan’s MTL and FiB indicators.
Aichi Biodiversity Targets
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.
Because commercial fishing tends to collectively and systematically catch the top level consumers in the marine food web (tunas, cods, groupers), when the marine ecosystem is under pressure from overfishing and its resilience is undermined, it is expected to see the ratio of top level consumers would decline and the ratio of low level consumers would arise, which is called "fishing down marine food webs". This index is used to monitor if the aforementioned phenomenon appears in the inshore and offshore waters of Taiwan.
Definition and Calculation
Take the relative fish landing of each marine organisms caught in the water of Taiwan in a certain year as the weight of the trophic level (fish landing of a certain species/total fish landing). By multiplying the trophic level weight and trophic level of a certain species, then summing all the results of multiplying up, the "mean trophic level" of a specific year is obtained. The annual change of the mean trophic level will reflect the status of the monitored organisms. If the number is declining, it may imply that the top level consumers in the marine ecosystem of a country are facing overfishing. This is defined as the mean trophic index.
The data is available until 2014 which comes the Region-based Marine Trophic Index of the catch in the waters of Taiwan in Sea Around Us.
Data Management Authorities
Fisheries Agency, Council of Agriculture