Pauly et al. labeled this phenomenon, “fishing down the food web” [1]. Upon publication, Pauly’s model of fishing down the food web garnered significant attention from both the scientific
and policy-making parties. A wave of subsequent studies identified regional examples of fishing down the food web and examined the relevant changes to fisheries management policy necessary to deal with this new understanding of exploitation effects [24], [25] and [26]. Most studies agreed with Pauly’s assertion that the decreasing MTL was a symptom of “overfishing, unsustainable harvest, and unintended ecological changes induced by widespread removal of species” [4]. Some scientists, however, were skeptical of the results and conclusions, citing gross assumptions buy RGFP966 of causality and methodological errors. In an attempt to examine the issue of causality, Essington et al. performed a closer analysis of the processes driving the trend of decreasing MTL. The researchers identified two underlying mechanisms that could
be responsible for a decrease in MTL. The first method is accurately BMS-777607 datasheet described by Pauly’s hypothesis of fishing down the food web: the replacement of high-trophic level species with low-trophic level species as abundance decreases. Essington labeled the second mechanism “fishing through the food web,” characterized by the addition of low-trophic level species to the fishery. The researchers analyzed worldwide catch data aggregated into six regions between 1950 and 2001 and identified a trend of decreasing MTL corroborating Pauly’s earlier findings. Their results further indicated that the fishing down model was only present in the North Atlantic. The pattern of change in target catch and landings in all
other regions of the world were more consistent with the fishing through scenario [4]. The study performed by Essington et al. represents a major development in the use of MTL as a diversity index. While this study reported similar findings of decreasing O-methylated flavonoid MTL across the world oceans, the authors identified a different mechanism to explain the change. Pauly et al. concluded that decreasing MTL reflected the sequential change of target catch from high to low trophic level as each stock collapsed. Essington et al., however, concluded that decreasing MTL could be due to the addition of lower trophic level stocks to targeted species. Both Pauly and Essington, however, recognized several limitations of their methodologies, perhaps the most important of which is a lack of precision in the available fisheries catch data, due to inaccurate reporting in some developing nations [1] and [4]. To address the methodological concerns of using catch-based MTL, Branch et al. performed a comparison of catch-based MTL and biomass-based MTL trends.