**Acknowledgements**

to certain biological parameters, on the other hand their effectiveness is in some cases hindered by the lack of surveillance and poor enforcement of protection regulations. In fact, these two factors seem the most important in determining the effectiveness of MPAs. Nonetheless, the implementation of MPAs even when unable to fully stop illegal harvest of limpet species, results in direct improvements for the protected populations in terms of abundance, size structure, and population density and indirect effects regarding reproductive output of these broadcast spawners. For this reason, the implementation of MPAs has become one of the most widely advocated tools for the management and conservation of coastal marine ecosystems in the recent decades

Several factors affect the response of protected populations, thus comparison between different MPAs is somewhat difficult. In fact, the recovery indicators reported for protected populations may be a consequence not only of MPA protection but also of changes in environmental conditions, biological characteristics of the species and, level of exploitation to which they are subjected [162–164]. The degree of exposure to wave action, as well as the vertical distribution of the species is thought to play an important role in the recovery of limpet populations; limpets more exposed to wave action as well as species exposed for longer periods to desiccation have a less pronounced response to the protection given by MPAs as shown by Branch and

Unsatisfactory results generally occur in those MPAs that are affected by inappropriate planning, ineffective surveillance, poor acceptance by local communities, and the lack of political will to reinforce the importance of environmental protection [140, 165–167]. For instance, Coppa et al. [159] concluded that although the designation of MPAs as a tool to preserve the remaining populations of the heavily exploited *P. ferruginea* is of extreme importance, for these MPAs to fulfil their goal, additional measures must be considered. In 2015, Coppa et al. [163] suggested that without a joint effort toward the protection of intertidal habitats by enforcement bodies, regulators, researchers, and sea users, the MPAs will not be able to achieve their conservation

The effectiveness of MPAs' conservation of limpet populations could be enhanced through the implementation of several additional measures that encompass a broader view of these exploited populations and the biological and ecological factors that influence their capacity to recover. For instance, it is necessary to determine which actions are required to ensure the reproductive success of individuals, essential to maintain the genetic biodiversity of overexploited species, particularly in species with absent gene flow between populations, since inbreeding increases the extinction probability of wild populations [168]. Also, the reintroduction or reinforcement of recruitment of depleted populations with allochthonous specimens produced by artificial fertilization procedures could be considered as a strategy to further

The establishment of MPAs as a conservation tool of marine coastal habitats and species has returned valuable contributions over the years, particularly in terms of density, abundance, and size structure of exploited species. However, to overcome limitations a possible route to improve the success of conservation strategies could be the establishment of networks of MPAs

[160, 161].

82 Organismal and Molecular Malacology

objectives.

Odendaal [88] for *C. oculus* in South Africa.

fulfil the MPAs' conservation objective [169].

ARDITI (Agência Regional para o Desenvolvimento da Investigação, Tecnologia e Inovação) is acknowledged for providing financial support for this work in the framework of the grant ARDITI-OOM/2016/010 (M1420-01-0145-FEDER-000001-Observatório Oceânico da Madeira-OOM). The third author (RS) was supported by a grant from ARDITI-OOM/2016/010 (M1420- 01-0145-FEDER-000001-Observatório Oceânico da Madeira-OOM).
