In a 2005 ecological model, Didier Gascuel demonstrated the effect of differing trophic location of target catch on fishery health. Gascuel concluded that high trophic

levels are the most sensitive to fishing pressure, noting that a 40% fishing effort would be considered full exploitation of species with a trophic level greater than 4. In contrast, full exploitation would be achieved at a fishing effort of 100% for trophic level 3 [27]. This demonstrated sensitivity of high trophic level species makes them especially prone to stock collapse. In a top-down driven ecosystem, where predator-prey interactions are the primary influence in ecosystem biomass and relative species abundance, an ecological extinction of top predators could create a trophic cascade [27]. Trophic cascades are defined by indirect effects of the

removal of a predator on the relative click here species abundance of lower trophic levels. While trophic cascades have been demonstrated in several marine ecosystems [28], [29] and [30], an especially relevant and well-documented example of a trophic cascade is that of the Atlantic Cod (Gadus morhua) in the Northwest Atlantic. Scientists, including both Pauly and Essington agree that the primary mechanism leading to the cod collapse is Selleckchem EPZ015666 that of intense overfishing. Upon the collapse of the cod fishery, fishing effort was redirected toward smaller pelagic species and macroinvertebrates, clearly illustrating the scenario of fishing down the food web [31]. In a 2005 study, Frank et al., explored the relationship between

biomass shifts of trophic levels on the Scotian Shelf of the North Atlantic. The researchers compared biomass estimates before the collapse of the cod fishery to estimates following the collapse. Abundance of top predators, including cod and other commercially important species experiencing significant declines in landings, was found to significantly correlate in the negative direction with abundance of small pelagic fishes and benthic macroinvertebrates. These small fishes and macroinvertebrates are the primary diet of top predators within the ecosystem. A positive correlation between top predator abundance and zooplankton abundance was identified, indicating a decrease in zooplankton abundance. Additionally, a negative correlation between top predator abundance and phytoplankton abundance was Urocanase evident. These interactions suggest that a decrease in the biomass of top predators caused an increase in abundance of their prey species (benthic macroinvertebrates), one trophic level lower. An increase in the abundance of benthic macroinvertebrates likely led to increased predation on zooplankton, thus decreasing zooplankton abundance. A decrease in the predation pressure by zooplankton would lead to the witnessed increase in phytoplankton biomass. To further support the hypothesis of a trophic cascade, Frank et al., examined the change in abundance of seals, a direct competitor of cod.