Fishing down is the scenario originally outlined by Pauly et al. where target catch is determined by a sequential catch and replace methodology, thus moving down the food web. Fishing through is the scenario proposed by Essington et al., where there is a sequential addition of lower trophic level species rather than a collapse of high-level stocks. Based on availability describes a scenario where abundant species are targeted first and as biomass decreases, Doxorubicin price target catch changes to species with a lower initial abundance. The based

on availability model, however, has received little supporting field evidence. Increase to overfishing represents a scenario where all species within an ecosystem are targeted and fishing pressure increases over time [5]. Branch et al. compiled models simulating each of the MTL-fishing scenarios, and concluded that fishing down will ultimately result in more collapsed species than fishing through. In addition, both scenarios would result in large stock depletion, but because all trophic levels will be affected, the catch-MTL and biomass-MTL would return to pre-exploitation levels. In contrast, the based on availability

scenario would result in a decline of catch MTL, but not biomass-MTL, and the increase to overfishing scenario would not affect MTL, but would result in a complete ecosystem collapse. Tariquidar Indeed, further analysis of worldwide target

catch revealed that most fisheries would fall under the scenario of increase to overfishing [5]. Due to these different relationships between catch and ecosystem MTL, Branch et al., concluded that MTL calculated with biomass estimates rather than catch data is generally more illustrative of ecosystem dynamics. The authors propose Roflumilast that natural fluctuations in pelagic species regimes, driven primarily by climactic factors, do not represent changes in overall ecosystem health, but would create drastic changes in catch (reflected in catch-MTL). When these stocks are removed from analyses, no decline in worldwide catch-MTL is evident, supporting their theory of an increased to overfishing scenario. Overall, Branch and his colleagues concluded that while MTL is a convenient measure of biodiversity due to the ease of calculation, the current understanding of factors contributing to the changing MTL and the relationship between MTL and fishing pressure is not adequate to rely upon for management decisions [5]. While it remains unclear which mechanism is primarily responsible for the changing MTL of the world’s oceans (fishing down, through, or increasing to overfishing), scientists agree that the ecological implications differ greatly depending upon the scenario of exploitation [1], [4] and [5].