Topic

In some areas of the Mediterranean Sea, intensive fishing can reduce the abundance of coastal fish which feed on sea urchins, allowing these to increase uncontrolled, and overgraze marine macrophyte forests. These habitats are biodiversity hotspots, supporting multiple species of organisms and the ecosystem services they provide. Additional to this ecological deterioration, fishing activities target other marine resources including invertebrates, among which sea urchins represent a relevant economic resource in some Mediterranean countries. In places where there is intensive sea urchin harvesting, the activity is becoming economically unsustainable, and the systematic removal of the main breeders (the largest sea urchins), together with stochastic events such as extreme storms or diseases may lead populations to collapse.

In this context, guaranteeing food security from natural resources while maintaining healthy marine forest ecosystems and conserving biodiversity remains a complex challenge for managers. To accomplish this purpose, it is necessary to deeply understand the processes regulating the ecological and socio-economic systems including the sea urchin Paracentrotus lividus that plays a key role, both as one of the main Mediterranean herbivores controlled by fish (mainly the commercial species of Sparids), and for its value as a highly prized delicacy especially in some Mediterranean areas.

MUrFor will be based in the Western Mediterranean Sea, where the reduction of fishes predating on sea urchins, manly seabreams (Sparidae), is leading to widespread sea urchin barrens, unproductive landscapes that rarely revert to the original macroalgal-dominated habitat (e.g., Catalonia). Concurrently, targeted harvesting of sea urchins is progressively increasing in many areas (e.g., Sardinia, some areas of Catalonia and Sicily) resulting in the collapse of local populations and of the related fisheries, with all the resulting negative socio-ecological consequences. As a result of these contrasting situations, most ecosystems in the Mediterranean are either approaching or are already beyond critical thresholds for conservation or fisheries viability. An Ecosystem-Based Fisheries Management (EBFM) is sorely needed to preserve the integrity of both marine forests and sea urchin populations. 

Our field studies will focus on comparing areas in which fishes and/or sea urchins are exploited under different levels of fishing pressure (from the fully-protected areas within the MPAs to the unprotected areas outside MPAs’ boundaries), in order to characterize the different management situations and document their consequences for the ecosystems and the fisheries.

 Most Mediterranean MPAs are characterized by healthy shallow rocky reef ecosystems that encompass large fishes, lush marine forests, and few large sea urchins. In contrast, exploited areas can either be characterized by barrens where sea urchins are the dominant organism, or by areas where sea urchins have been overharvested, indirectly affecting the structure of the community. In addition, we will also include areas with different environmental conditions (nutrients and temperature) since these are known to

be critical in determining ecosystem thresholds. A comparative approach across areas and a coupled experimental and modeling perspective can provide concrete support to EBFM, which has rarely been implemented in similar systems across the globe.