An important principle of environmental science is that changes in single components of systems are likely to have consequences elsewhere in the same systems. In the sea, food web data are one of the few foundations for predicting such indirect effects, whether of fishery exploitation or following recovery in marine protected areas (MPAs). We review the available literature on one type of indirect interaction in benthic marine ecosystems, namely trophic cascades, which involve three or more trophic levels connected by predation. Because many indirect effects have been revealed through fishery exploitation, in some cases we include humans as trophic levels. Our purpose is to establish how widespread cascades might be, and infer how likely they are to affect the properties of communities following the implementation of MPAs or intensive resource exploitation. We review 39 documented cascades (eight of which include humans as a trophic level) from 21 locations around the world; all but two of the cascades are from shallow systems underlain by hard substrata (kelp forests, rocky subtidal, coral reefs and rocky intertidal). We argue that these systems are well represented because they are accessible and also amenable to the type of work that is necessary. Nineteen examples come from the central-eastern and north-eastern Pacific, while no well-substantiated benthic cascades have been reported from the NE, CE or SW Atlantic, the Southern Oceans, E Indian Ocean or NW Pacific. The absence of examples from those zones is probably due to lack of study. Sea urchins are very prominent in the subtidal examples, and gastropods, especially limpets, in the intertidal examples; we suggest that this may reflect their predation by fewer specialist predators than is the case with fishes, but also their conspicuousness to investigators. The variation in ecological resolution amongst studies, and in intensity of study amongst systems and regions, indicates that more cascades will likely be identified in due course. Broadening the concept of cascades to include pathogenic interactions would immediately increase the number of examples. The existing evidence is that cascade effects are to be expected when hard-substratum systems are subject to artisanal resource exploitation, but that the particular problems of macroalgal overgrowth on Caribbean reefs and the expansion of coralline barrens in the Mediterranean rocky-sublittoral will not be readily reversed in MPAs, probably because factors other than predation-based cascades have contributed to them in the first place. More cascade effects are likely to be found in the soft-substratum systems that are crucial to so many large-scale fisheries, when opportunities such as those of MPAs and fishing gradients become available for study of such systems, and the search is widened to less conspicuous focal organisms such as polychaetes and crustaceans.

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Marine protected areas (MPAs) have largely proven to be effective tools for conserving marine ecosystem, while socio-economic benefits generated by MPAs to fisheries are still under debate. Many MPAs embed a no-take zone, aiming to preserve natural populations and ecosystems, within a buffer zone where potentially sustainable activities are allowed. Small-scale fisheries (SSF) within buffer zones can be highly beneficial by promoting local socio-economies. However, guidelines to successfully manage SSFs within MPAs, ensuring both conservation and fisheries goals, and reaching a win-win scenario, are largely unavailable. From the peer-reviewed literature, grey-literature and interviews, we assembled a unique database of ecological, social and economic attributes of SSF in 25 Mediterranean MPAs. Using random forest with Boruta algorithm we identified a set of attributes determining successful SSFs management within MPAs. We show that fish stocks are healthier, fishermen incomes are higher and the social acceptance of management practices is fostered if five attributes are present (i.e. high MPA enforcement, presence of a management plan, fishermen engagement in MPA management, fishermen representative in the MPA board, and promotion of sustainable fishing). These findings are pivotal to Mediterranean coastal communities so they can achieve conservation goals while allowing for profitable exploitation of fisheries resources.

ABSTRACT1. We present in this review a general description of marine protected areas (MPAs) in the northwestern Mediterranean and some general principles for the establishment of protected areas, including their size, location, biotope composition, regulation, and management.2. Many Mediterranean MPAs are located around or adjacent to islands, but the placement of a marine reserve close to a large urban area is not necessarily a handicap, as has been demonstrated by some examples. It is not, therefore, necessary to restrict future MPAs solely to regions of low human density.3. The conceptual question of MPA size (single large or several small SLOSS debate) has never been explicitly considered in the selection of Mediterranenan MPAs. However, studies of fish recruitment in MPAs, and the development of a network of small MPAs between Spain and France have highlighted the importance and value of small sized MPAs (200 -2000 ha).4. Whatever the location of a future MPA, its success as measured in terms of stock restoration will depend on whether (i) sufficient suitable habitat is available, (ii) the variety and abundance of prey species are adequate and (iii) the possibilities for recruitment of the biota are reasonable.5. The initial choices of zonation and legislation regulating the management of any future MPA are of primary importance. The zonation plan should be as simple as possible (gradation of 2 or 3 levels) and it should be acknowledged that the significance of management conflicts within a MPA will be inversely proportional to the extent of preliminary consultations with all of the users, both professional and amateur.6. The examples of semi-protected areas where professional fishing is still allowed demonstrate without ambiguity the negative impact of spear-fishing, and the limited impacts from regulated professional activities on fish assemblages. The means of regulating consist essentially of (i) a prohibition of certain type of fishing methods (trawling); and (ii) a limitation of the numbers of fishermen by a system of restriction or authorization.7. In the MPAs examined, there is a great diversity of situations in relation to the size of and distribution of duties between staff assigned to their management. However, the single most

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