  The concentration of the population in coastal regions, in addition to the
direct human use, is leading to an accelerated process of change and
deterioration of the marine ecosystems. Human activities such as fishing
together with environmental drivers (e.g. climate change) are triggering major
threats to marine biodiversity, and impact directly the services they provide.
In the South and Southwest coasts of Portugal, the deep-water crustacean trawl
fishery is not exemption. This fishery is recognized to have large effects on a
number of species while generating high rates of unwanted catches. However,
taking into account an ecosystem-based perspective, the fishing impacts along
the food web accounting for biological interactions between and among species
caught remains poorly understood. These impacts are particularly troubling and
are a cause of concern given the cascading effects that might arise. Facing the
main policies and legislative instruments for the restoration and conservation
of the marine environment, times are calling for implementing ecosystem-based
approaches to fisheries management. To this end, we use a food web modelling
(Ecopath with Ecosim) approach to assess the fishing impacts of this particular
fishery on the marine ecosystem of southern and southwestern Portugal. In
particular, we describe the food web structure and functioning, identify the
main keystone species and/or groups, quantify the major trophic and energy
flows, and ultimately assess the impact of fishing on the target species but
also on the ecosystem by means of ecological and ecosystem-based indicators.
Finally, we examine limitations and weaknesses of the model for potential
improvements and future research directions.
