12 April 2010

Overfishing in a coastal ecosystem in Greece

A collaboration between Tethys researchers and the University of British Columbia Fisheries Centre in Vancouver has recently resulted in a new paper: “Effects of local fisheries and ocean productivity on the northeastern Ionian Sea ecosystem”.

The study considers the time span 1964-2008 and 22 functional groups including dolphins, tuna, swordfish, monk seals, sea turtles as well as plankton, crustaceans and detritus.

Application of Ecopath with Ecosim highlighted a decline of top predators since the late 1970s. Decline of commercial fish resources, caused by overfishing, provoked a cascade-up effect through the ecosystem and had important negative consequences on species such as the short-beaked common dolphin - that almost vanished in this part of Greece.

The study was published in Ecological Modelling.


Piroddi C., Bearzi G., Christensen V. 2010. Effects of local fisheries and ocean productivity on the northeastern Ionian Sea ecosystem. Ecol. Model. doi:10.1016/j.ecolmodel.2010.03.002

Abstract -- To better understand the effects of fisheries and ocean productivity on the northeastern Ionian Sea we constructed an Ecopath with Ecosim model with 22 functional groups. Data on biomass, production/biomass, consumption/biomass, and diet for each group were estimated or extrapolated from the literature. Fisheries landings and discards were also included. Temporal trajectories were simulated using Ecosim. The model was fitted with time-series data for the most important groups from 1964 to 2006. Simulations highlighted a decline of top predators and of most of the commercial species since the late 1970s. The model shows that the decline of fish resources was mainly caused by an intensive fishing pressure that occurred in the area until the end of the 1990s and also by changes in primary production that impacted the trajectories of the main functional groups. In particular, simulated changes through time in PP impacted the abundance trends of all the commercial species, showing a cascade-up effect through the ecosystem. The application of Ecopath with Ecosim was a useful tool for understanding the trends of the main functional groups of the northeastern Ionian Sea. The model underlined that management actions are needed to restore and protect target species including marine mammals, pelagic and demersal fishes. In particular, measures to reduce overfishing, illegal fishing activities and to respect existing legislations are in need. Moreover, the adoption of marine protected areas could be an effective management measure to guarantee prey survival and to sustain marine predators.

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