Introduction
The Habitat Directive (HD) require Member States to implement surveillance of the conservation status of species of Community interest listed in Annexes II, IV, and V. According to the European guidelines, the assessments of species must be carried out at a biogeographical scale by implementing monitoring activities to gather information on specific parameters, such as ‘Range’ (based on actual distribution), ‘Population’, ‘Habitat for the species’, and ‘Future Prospects’. The results of these activities must be reported to the European Commission every six years with the preparation of a National Report, drawn up based on specific community standards and templates. Monitoring activities should be planned to collect data both within and outside the sites of the Natura 2000 (N2k) network, so that the conservation status of species at the national scale and the contribution of this network to the achievement of the HD objectives can be assessed (DG Environment, 2023).
The results of Italy’s Fourth National Report (2012–2018 reporting cycle), despite a significant advancement in knowledge compared to the previous cycle, highlighted the need, especially in the marine environment, to define specifically designed monitoring plans, based on the application of standardised methodologies and protocols (La Mesa et al., Reference La Mesa, Lauriano, Mo, Paglialonga and Tunesi2021). A useful methodological support for planning monitoring activities on species and habitats of community interest has been recently provided by La Mesa et al. (Reference La Mesa, Paglialonga and Tunesi2019).
Especially for some species of marine invertebrates, such as Patella ferruginea (Gastropoda, Patellidae), Pinna nobilis (Bivalvia, Pinnidae), Lithophaga lithophaga (Bivalvia, Mytilidae), Centrostephanus longispinus (Echinoidea, Diadematidae), and Scyllarides latus (Malacostraca, Scyllaridae), the lack of monitoring activities carried out in a coordinated way at the national scale using standardised protocols has led in the last HD reporting round to the frequent use of expert judgement, not only in assessing species conservation status but also in the creation of distribution maps (La Mesa et al., Reference La Mesa, Lauriano, Mo, Paglialonga and Tunesi2021). Knowledge gaps on the actual presence and abundance of these species along the Italian coast particularly affect unprotected coastal areas. The major official source of information on their distribution range is the standard data forms, which include the faunal composition of the N2k sites (EEA, 2025). However, the lack of periodic surveys dedicated to monitoring these species often makes this information outdated and/or unreliable.
In the literature, the most detailed and recent information on the distribution of P. ferruginea, a species endemic to the western Mediterranean, along the Italian coasts is reported by Espinosa et al. (Reference Espinosa, Rivera-Ingraham, Maestre, González, Bazairi and García-Gómez2014), Ferranti et al. (Reference Ferranti, Guallart, Asnaghi and Chiantore2023), and Cascales-Soler et al. (Reference Cascales-Soler, Ramos-Espla and Forcada2023). These authors identified the largest islands Sardinia and Sicily as well as the coasts of Tuscany and Liguria as areas of greatest occurrence of the species. This species, which lives only in the western Mediterranean basin, was indiscriminately harvested in the past, before the implementation of the Habitats Directive, ensuring its protection (Espinosa et al., Reference Espinosa, Rivera-Ingraham, Maestre, González, Bazairi and García-Gómez2014).
The noble pen shell P. nobilis, another endemic Mediterranean species, has been affected over the last seven years by a mass mortality event (MME) on a Mediterranean-wide scale (Carella et al., Reference Carella, Prado, De Vico, Palić and Villari2023 and references therein). The cause of this MME has been attributed to the combined effect of two main pathogens, Haplosporidium pinnae and Mycobacterium spp. (Catanese et al., Reference Catanese, Grau, Valencia, Garcia-March, Vazquez-Luis, Alvarez, Deudero, Darriba, Carballal and Villalba2018; Grau et al., Reference Grau, Villalba, Navas, Hansjosten, Valencia, García-March, Prado, Follana-Berná, Morage, Vázquez-Luis, Álvarez, Katharios, Pavloudi, Nebot-Colomer, Tena-Medialdea, Lopez-Sanmartín, Peyran, Čižmek, Sarafidou, Issaris, Tüney-Kizilkaya, Deudero, Planes and Catanese2022), although recent findings suggest a more complex scenario (Carella et al., Reference Carella, Prado, De Vico, Palić and Villari2023). In 2021, this species was assessed against the IUCN Red List categories and criteria and listed as ‘Critically Endangered’ due to the basin-scale mass mortality. A systematic review of the occurrence of P. nobilis in the Mediterranean Sea, combining different sources of information, was proposed by Marrocco et al. (Reference Marrocco, Zangaro, Sicuro and Pinna2019). At a lower spatial scale, an investigation on distribution, abundance, and mortality of pen shell was conducted in the Apulia region (southeast of Italy) (Pensa et al., Reference Pensa, Fianchini, Grosso, Ventura, Cataudella, Scardi and Rakaj2022). To date, our knowledge on the species’ distribution and the effect of the MME along the Italian coasts remains incomplete or outdated.
The most up-to-date information on the occurrence of L. lithophaga in Italian seas is reported in the work of Colletti et al. (Reference Colletti, Savinelli, Di Muzio, Rizzo, Tamburello, Fraschetti, Musco and Danovaro2020), which examines the actual spatial extent and distribution of fishing damage caused by the date mussel in subtidal rocky habitats throughout the Mediterranean Sea.
To our knowledge, there are no recently published reports on the distribution of C. longispinus and S. latus, whose presence has been only documented in faunistic inventories of small-sized areas (Canessa et al., Reference Canessa, Bavestrello, Guidetti, Navone and Trainito2022; Colletti et al., Reference Colletti, Oliveira, Bernardi and Cerrano2019).
In Italy, the implementation of monitoring activities on species of community interest is entrusted to regional authorities. Regarding activities at sea, these authorities can refer to the staff of Regional Agencies for Environmental Protection (ARPAs). Budgetary constraints and the lack of established standards are frequently claimed by these authorities as the most relevant limiting factors for the implementation of regular monitoring activities on a national scale with regional specificity.
To address these problems, a pilot monitoring programme focusing on the aforementioned invertebrate species was started in 2022 with the involvement of various institutional bodies. Field surveys were conducted to collect data at a regional scale on P. ferruginea, P. nobilis, and L. lithophaga through the cooperation of some ARPAs. Conversely, monitoring activities on C. longispinus and S. latus were carried out at six pilot areas, by involving the management bodies of six Italian marine protected areas (MPAs), chosen to cover the different Italian marine subregions.
In the present work, data collected through this monitoring programme were analysed and discussed to provide updated information on the distribution of the investigated invertebrates, which is useful for the definition of future monitoring plans. Moreover, the strengths and weaknesses of the applied approach and experimental protocols were identified and some methodological improvements suggested.
Material and methods
Study area
The study areas for the investigated species were selected based on various criteria. Monitoring activities on P. ferruginea, P. nobilis and L. lithophaga were carried out according to a regional spatial design, involving the respective regional agencies (Table 1) and selecting as primary options already known areas of occurrence. Further investigation on the presence of P. nobilis was conducted at three sites located within the Venetian lagoon, to assess the importance of these brackish environments for the survival of the species.
Geographic distribution of monitoring areas (Italian regions and marine protected areas) for the species investigated
Field surveys of S. latus and C. longispinus were conducted at six pilot areas corresponding to six MPAs. These were representative of different Mediterranean sectors and recognised as Specially Protected Areas of Mediterranean Importance (SPAMI) by the Barcelona Convention (Table 1).
The geographical distribution of survey areas for each species is shown in Figure 1.
Map of the study area showing the location of the monitoring areas for the investigated species.
Data collection methodology
Monitoring activities were conducted by using the standardised experimental methodologies and protocols oulined in the handbook of La Mesa et al. (Reference La Mesa, Paglialonga and Tunesi2019).
In the survey method used for P. ferruginea, visual counts of limpets were performed along transects laid parallel to the shoreline in the intertidal zone. The surveys were carried out in 32 areas, generally in three localities per area, spread across seven Italian administrative regions (Liguria, Tuscany, Sardinia, Campania, Basilicata, Calabria, and Sicily). At each locality, 10 georeferenced transects, each 25 m long, were surveyed by snorkelling and/or by boat. Biometric characteristics (shell length, width, and height) and morphological types of each observed specimen were measured with a calliper to the nearest millimetre (Coppa et al., Reference Coppa, de Lucia, Massaro and Magni2012). Environmental features (substrate nature, slope, wave exposure, site accessibility) of the investigated coastal stretch were also recorded during the surveys to assess the most suitable habitat characteristics for the species.
Monitoring of P. nobilis was conducted by visual censuses along georeferenced linear transects (100 × 6 m, i.e. 600 m2). A total of 89 survey areas were considered, each represented by three locations, divided into 11 Italian regions (Liguria, Tuscany, Sardinia, Latium, Campania, Basilicata, Calabria, Sicily, Apulia, Veneto, and Friuli-Venezia Giulia). All specimens observed within the transects were counted, and their biometric characteristics (maximum and minimum width and unburied length of the shell) measured with a ruler by scuba divers (García-March and Vicente, Reference García-March and Vicente2006). The health status of each specimen and the abiotic characteristics (habitat type, bottom depth) of the sighting site were finally recorded. The presence of P. nobilis at Venetian lagoon sites was monitored using the same methodology. However, in this case, the surveys were conducted in specific areas (called ‘velme’) and under dry condition, taking advantage of the short periods of complete substrate emergence they were subjected to.
To obtain a more comprehensive view of the presence and abundance of P. ferruginea and P. nobilis in the national territory, data collected during previous years (between 2018 and 2020) within the national monitoring activities for the Marine Strategy Framework Directive (2008/56/CE) were added to the data set.
Monitoring of L. lithophaga was carried out using an indirect survey method, which employs habitat quality (defined by the extent of damage present on the substrate) as a proxy for assessing the conservation status of the species. Surveys on this species covered 22 localities, located in seven Italian regions (Liguria, Latium, Campania, Sicily, Apulia, Marche, and Friuli-Venezia Giulia).
After identifying coastal areas characterised by the presence of substrate suitable for the species (typically calcareous rocky substrate, vertical or subvertical, either natural or artificial), scuba diving surveys were conducted along georeferenced horizontal stretches of coastline. In each 100 m long stretch, four transects (20 × 1 m, i.e. 20 m2) 5 m apart were surveyed, to estimate the intensity of damage following the methodology proposed by Fanelli et al. (Reference Fanelli, Piraino, Belmonte, Geraci and Boero1994).
Semi-quantitative data on the presence of C. longispinus and S. latus, species frequently hidden in crevices and most active at night, can be ‘opportunistically’ collected by non-scientists according to a citizen science approach (La Mesa et al., Reference La Mesa, Paglialonga and Tunesi2019). To accomplish this task, the MPA managers actively engaged diving centres and professional fishermen licenced to operate within the MPA to provide sighting and catch data on these species. Specifically, recreational divers and fishermen were asked to provide information on the (a) size of individuals observed/fished, (b) georeferenced location and abiotic characteristics (bottom depth, habitat type) of the sighting/capture site, and (c) operational aspects (diving time, fishing gear used).
Results
Patella ferruginea
Data on species abundance expressed as the number of individuals detected per linear metre of coastline and its distribution along the investigated coastal stretches are shown in Figure 2. The 10 × 10 km grid used for European reporting of the Habitats Directive (Article 17) was used to represent this distribution. The highest densities were observed in northern Sardinia (La Maddalena Archipelago), western Sicily (Egadi Islands), western Calabria and some localities of Liguria (Punta Mesco and Cinque Terre). A total of 180 specimens were recorded, indicating a rather small and highly localised population size. The size (shell length) of limpets and some abiotic characteristics of the coastal stretches at the monitoring sites are provided in Table 2. The average size is greater than 38 mm at all sites except those in Basilicata and Calabria, where the average size is less than 21 mm. Most of the sites of the species occurrence were characterised by steep substrate slope, high wave exposure, and difficult accessibility.
Density map of Patella ferruginea in the monitoring areas showing the species abundance (number of individuals per linear meter of coastline) within 10 × 10 km grid. The boundaries of the Italian regions are indicated.
Abundance (total no. of individuals) and size (shell length) of P. ferruginea at the monitoring sites of the Italian regions. Some abiotic characteristics (substratum slope, wave exposure and accessibility level) of the costal stretches are also given
Pinna nobilis
The abundance of P. nobilis (total number of live and dead individuals observed) in the monitoring areas is shown in Figure 3, using the same graphical representation (the 10 × 10 km grid) used for P. ferruginea. The highest abundance values were observed in Veneto, Friuli-Venezia Giulia, Sardinia and Tuscany. The same distribution pattern can be observed by plotting the abundance of live individuals (Figure 4). Comparing the two maps it is evident that viable specimens constituted only a small proportion of the populations. The highest percentages of viable individuals were recorded during the first series of campaigns, carried out between 2018 and 2020, testifying to a gradual and large-scale die-off.
Density map of Pinna nobilis in the monitoring areas showing the species abundance (total number of individuals) within 10 × 10 km grid. The boundaries of the Italian regions are indicated.
Density map of Pinna nobilis in the monitoring areas showing the species abundance (number of live individuals) within 10 × 10 km grid. The boundaries of the Italian regions are indicated.
This negative trend is effectively documented by the data reported in Table 3, showing the species abundance in the localities monitored several times between 2018 and 2023. It is further illustrated by comparing the number of viable individuals observed in the period 2018–2020 with those recorded during the period 2022–2023 (Figure 5). In most localities, the population size showed a drastic downward trend, particularly in terms of viable individuals. In Friuli-Venezia Giulia, although the total number of individuals did not decline during the study period, the percentage of live specimens in two localities dropped from values close to 100% to 0%.
Density map of Pinna nobilis in the monitoring areas showing the species abundance (number of live individuals) recorded in the period 2018–2020 and 2022–2023 within 10 × 10 km grid. The boundaries of the Italian regions are indicated.
Abundance (total no. of individuals) of P. nobilis at the localities of the Italian regions monitored several times between 2018 and 2023. Percentages of viable individuals are in brackets
Lithophaga lithophaga
The monitoring data for L. lithophaga, collected by assessing the quality of the habitat for the species and expressed in terms of the intensity of damage, are graphically represented in Figure 6. The most critical situations for the species were observed in few localities of Liguria, Campania and Apulia, where the intensity of damage to the habitat was medium or high. However, in most of the monitored sites, no evidence of harvesting was found.
Density map of Lithophaga lithophaga in the monitoring areas showing the intensity of damage on the species rocky habitat within 10 × 10 km grid. The boundaries of the Italian regions are indicated.
Centrostephanus longispinus and Scyllarides latus
Semi-quantitative data on C. longispinus and S. latus, collected through citizen science methods (sightings during recreational dives and catch data from professional fishermen operating in the six MPAs involved in the project), are summarised in Table 4. To provide a rough estimate of the sampling effort, the number of fishermen and diving centres involved in data collection is also reported (Table 4). A total of 323 specimens of C. longispinus were recorded, about half of which were observed in the Punta Campanella MPA.
Abundance (no. of individuals) of Centrostephanus longispinus and Scyllarides latus recorded in the marine protected areas (MPAs) by recreational divers or professional fishermen. The sampling effort expressed by the number of fishermen and diving centres involved in data collection is also reported
The total number of records of S. latus was 271, 66% of which were provided by recreational divers. The catch data showed a prevalence of large to medium-sized individuals, with small individuals comprising 11%. About half of the divers’ records involved large specimens, while the remaining half was evenly divided between medium and small specimens.
Discussion
This paper presents an up-to-date overview of the distribution and abundance patterns of five marine invertebrate species of the European Community interest, four of which (P. ferruginea, P. nobilis, L. lithophaga, and C. longispinus) are listed in Annex IV (which includes species whose conservation status requires strict protection) and one species (Scyllarides latus) in Annex V (whose exploitation is required to be object of management measures). Considerable monitoring efforts were made through the implementation of the described programme that, for the first time in Italy, was conducted in a coordinated manner on a national scale, using standardised experimental protocols. The ecological differences among the monitored species necessitated the use of diverse study methodologies and sampling strategies. These approaches were both scientifically sound, ensuring the collection of consistent data with adequate spatial coverage, and sustainable in cost/benefit terms.
The analysis of the data collected through these monitoring activities revealed significant interspecific differences linked to multiple intrinsic and extrinsic factors, offering interesting insights into the vulnerability of the investigated species.
The presence of P. ferruginea along the monitored coastlines was extremely localised and often characterised by very small schools of or isolated limpets. These findings substantially agreed with the distribution pattern of the species recently reported by Ferranti et al. (Reference Ferranti, Guallart, Asnaghi and Chiantore2023), particularly regarding the location of the species hotspots. The first occurrence of P. ferruginea at sites still unexplored (Acquafredda di Maratea and Isola di S. Ianni in Basilicata) or at sites previously monitored by other researchers (e.g. the Island of Cirella in the western coast of Calabria) (Ferranti et al., Reference Ferranti, Guallart, Asnaghi and Chiantore2023) was remarkable.
The distribution pattern of P. ferruginea, mostly restricted to poorly accessible stretches of coastline in remote and/or protected areas, confirmed the role of human harvesting as a driving factor in the rarefaction of populations in recent decades (Bazairi et al., Reference Bazairi, Salvati, Benhissoune, Tunesi, Rais, Agnesi, Benhamza, Franzosini, Limam, Mo, Molinari, Nachite and Sadki2004). As observed in other areas of the Mediterranean, illegal harvesting, mostly practiced in easily accessible and unprotected coastal areas, has been a major cause of the species’ regression and alterations in population structure (Doukara, Reference Doukara2019; Espinosa et al., Reference Espinosa, Rivera-Ingraham, Maestre, González, Bazairi and García-Gómez2014; Guerra-García et al., Reference Guerra-García, Corzo, Espinosa and García-Gómez2004; Luque et al., Reference Luque, Guallart, Templado and Pola2018; Tlig-Zouari et al., Reference Tlig-Zouari, Othman, Fguiri and Ben Hassine2010; Zarrouk et al., Reference Zarrouk, Romdhane and Espinosa2016). According to recent studies, the dispersal capacity of limpets would not be one of the main limiting factors for the species’ survival (Ferranti et al., Reference Ferranti, Guallart, Asnaghi and Chiantore2023).
The illegal harvesting of P. ferruginea, mainly targeting large individuals (i.e. female specimens with the greatest reproductive capacity), can drastically affect the reproductive viability of this protandrous hermaphrodite species (Espinosa et al., Reference Espinosa, Guerra-García, Fa and García-Gómez2006; Guerra-García et al., Reference Guerra-García, Corzo, Espinosa and García-Gómez2004; Luque et al., Reference Luque, Guallart, Templado and Pola2018). As reported elsewhere, P. ferruginea limpets are collected for food or used as bait by fishermen (Guerra-García et al., Reference Guerra-García, Corzo, Espinosa and García-Gómez2004; Luque et al., Reference Luque, Guallart, Templado and Pola2018). To effectively hinder the harvesting of this and other species of conservation interest, it is necessary not only to increase surveillance and enforce the penalties established but also to implement community awareness-raising initiatives on the detrimental effects that illegal activities can have on the survival of these species (Coppa, Reference Coppa2011; Guerra-García et al., Reference Guerra-García, Corzo, Espinosa and García-Gómez2004; Marra et al., Reference Marra, de Lucia, Camedda, Espinosa and Coppa2015). The widespread lack of knowledge about the existence of threatened species protected by EU regulations, such as P. ferruginea, is, in fact, one of the main reasons for the persistence of illegal harvesting activities. Disseminating knowledge about these species also increases public awareness and propensity to participate in citizen science projects with direct benefit to the scientific community.
Data collected on P. nobilis clearly confirmed the extremely critical situation of this endemic species in all Italian seas, due to the MME affecting the entire Mediterranean. The decline in the P. nobilis populations over the study period (five years) is attested not only by a significant decrease in the number of individuals detected, but mostly by the almost total disappearance of viable individuals. This phenomenon has also affected areas, such as the Friuli-Venezia Giulia coasts, where dozens of healthy individuals had been recorded until 2019. Since the end of 2019, some cases of pen shell MMEs have been recorded from the southernmost areas of the Adriatic northwards. In summer 2020, no live pen shells were found during an extensive survey carried out along the entire Apulian coastline (Pensa et al., Reference Pensa, Fianchini, Grosso, Ventura, Cataudella, Scardi and Rakaj2022). The spread of MMEs in the northern Adriatic Sea has been documented in recent years (2019–2020) along the Croatian coasts, where Čižmek et al. (Reference Čižmek, Čolić, Gračan, Grau and Catanese2020) observed mortality rates ranging from 36% to 100% of pen shells.
Nowadays, the sites of greatest value for the survival of the species are those located within the Venetian Lagoon, where 20% to 70 % of viable individuals were recorded in 2023. This confirms that, in transitional waters, the virulence of the parasitosis affecting this species is less successful. Indeed, the spread of pathogens in lagoon systems could be hampered by the low water exchange, low salinity, and high seasonal fluctuations in environmental parameters that characterise these environments (Cabanellas-Reboredo et al., Reference Cabanellas-Reboredo, Vázquez-Luis, Mourre, Alvarez, Deudero, Amores, Addis, Ballesteros, Barrajón, Coppa, García-March, Giacobbe, Giménez Casalduero, Hadjioannou, Jiménezgutiérrez, Katsanevakis, Kersting, Mačić, Mavrič, Patti, Planes, Prado, Sánchez, Tena-Medialdea, De vaugelas, Vicente, Zohra Belkhamssa, Zupan and Hendriks2019; Foulquié et al., Reference Foulquié, De la grandrive R, Dalias and Vicente2020). Even in this area, the species has undergone a significant decline in abundance over the last decade, decreasing from 12–16 individuals/m2 in 2012 (Russo, Reference Russo2012) to 0.04–0.16 individuals/m2 in 2023 (present study). Population densities similar to those recorded in the Venice Lagoon were reported in the spring and summer of 2018–2019 in the lagoon of Marano and Grado (Curiel et al., Reference Curiel, Miotti, Checchin, Rismondo, Pierini, Zucchetta, Bettoso and De Luca2020), where the average species density ranged between 0.003 and 0.153 individuals/m2. A small nucleus of viable pen shells was recently observed at Lake Faro, a small lagoon in north-eastern Sicily (Donato et al., Reference Donato, Lunetta, Spinelli, Catanese and Giacobbe2023). The presence of numerous dead individuals in all the aforementioned lagoons suggests that the effects of parasitosis are far from negligible, also in such environments.
The critical situation of P. nobilis currently observed along the Italian coasts and, some years ago, in other Mediterranean countries (Vázquez-Luis et al., Reference Vázquez-Luis, Álvarez, Barrajón, García-March, Grau, Hendriks, Jiménez, Kersting, Moreno, Pérez, Ruiz, Sánchez, Villalba and Deudero2017), indicates that the MME that began in 2016 is still onging, and no local population can be considered safe. Hence, it is essential for the species’ survival to identify natural shelters (such as lagoon systems), where viable populations may persist, and protect them in a timely manner. As outlined by Kersting et al. (Reference Kersting, Vázquez-Luis, Mourre, Belkhamssa, Álvarez, Bakran-Petricioli, Barberá, Barrajón, Cortés, Deudero, García-March, Giacobbe, Giménez-Casalduero, González, Jiménez-Gutiérrez, Kipson, Llorente, Moreno, Prado, Pujol, Sánchez, Spinelli, Valencia, Vicente and Hendriks2020), unaffected pen shell populations could play a crucial role in the species’ recovery through larval exporting in surrounding sites.
Given the rapid spread of the pathogen and the high mortality outbreak of infected populations, a systematic regular monitoring is highly recommended along the whole Mediterranean (IUCN, 2018). New research effort should be devoted to understanding the response of surviving individuals and populations at specific locations such as marine lagoon environments (IUCN, 2018). Field studies conducted in various areas and at different depths might reveal more locations with live populations. As suggested by Zotou et al. (Reference Zotou, Gkrantounis, Karadimou, Tsirintanis, Sini, Poursanidis, Azzolin, Dailianis, Kytinou, Issaris, Gerakaris, Salomidi, Lardi, Ramfos, Akrivos, Spinos, Dimitriadis, Papageorgiou, Lattos, Giantsis, Michaelidis, Vassilopoulou, Miliou and Katsanevakis2020), it should be interesting to expand monitoring activities of the species at greater depths than those usually monitored (<30 m) to assess the status of P. nobilis populations in the deeper part of their depth range (i.e. 30–60 m).
Finally, to protect the few currently unaffected population and counteract the illegal harvesting of P. nobilis, still occurring in some Mediterranean areas (e.g. Greece), it is advisable to ensure a better legislation enforcement and increase public awareness (Cabanellas-Reboredo et al., Reference Cabanellas-Reboredo, Vázquez-Luis, Mourre, Alvarez, Deudero, Amores, Addis, Ballesteros, Barrajón, Coppa, García-March, Giacobbe, Giménez Casalduero, Hadjioannou, Jiménezgutiérrez, Katsanevakis, Kersting, Mačić, Mavrič, Patti, Planes, Prado, Sánchez, Tena-Medialdea, De vaugelas, Vicente, Zohra Belkhamssa, Zupan and Hendriks2019).
The overall picture that emerged from the present study on the presence and health status of L. lithophaga populations, inferred indirectly through the assessment of the conservation status of rocky substrates colonised by the species, indicates the persistence of illegal fishing activities in at least some of the areas investigated. Previous studies reported that the illegal harvesting of date mussels is widely practiced in Italy and in other Mediterranean countries, also within MPAs, despite national and international legislations protecting this species and rocky reef habitats (Colletti et al., Reference Colletti, Savinelli, Di Muzio, Rizzo, Tamburello, Fraschetti, Musco and Danovaro2020; Katsanevakis et al., Reference Katsanevakis, Poursanidis, Issaris, Panou, Petza, Vassilopoulou, Chaldaiou and Sini2011).
In recent decades, some research on the impact of date mussel fishery in Italy were carried out in Liguria, Apulia, Campania, and Sardinia (Fanelli et al., Reference Fanelli, Piraino, Belmonte, Geraci and Boero1994; Fraschetti et al., Reference Fraschetti, Bianchi, Terlizzi, Fanelli and Morri2001; Guidetti and Boero, Reference Guidetti and Boero2004; Guidetti et al., Reference Guidetti, Fraschetti, Terlizzi and Boero2003; Russo and Cicogna, Reference Russo and Cicogna1992).
Along the Ligurian coast, evidence of date mussel fishery was collected by Seveso (Reference Seveso2005) at Cape Noli, one of the locations where we found the greatest level of impact on the rocky substrate. The impact of date mussel fishery along the Apulian coasts was first investigated by Fanelli et al. (Reference Fanelli, Piraino, Belmonte, Geraci and Boero1994), who reported damage caused by this illegal practice in more than 60 % of the monitored coastline. In the same area, further studies in the following years and our monitoring activities showed that this destructive fishery practice continued, with serious impacts on different ecosystem components (Fraschetti et al., Reference Fraschetti, Bianchi, Terlizzi, Fanelli and Morri2001; Guidetti and Boero, Reference Guidetti and Boero2004; Guidetti et al., Reference Guidetti, Fraschetti, Terlizzi and Boero2003).
The Sorrento-Amalfi Peninsula is one of the areas in Campania where a high level of habitat degradation was found, in agreement with Russo and Cicogna (Reference Russo and Cicogna1992) who noted that 85% of the investigated reef area (about 70 km coastline) was severely or moderately damaged due to date mussels harvesting. In the early 1990s, fishing of L. lithophaga was intensively practiced in some areas of southern Sardinia (the Cagliari Gulf and the Palmas Gulf) (Cuccu et al., Reference Cuccu, Addis, Lenza, Stefani and Campisi1994), but unfortunately no updated information is available. Our investigation documented for the first time the presence of illegal exploitation of this species in southern Latium.
Although date mussel fishing is prohibited by law, the persistence of indiscriminate harvesting of the species is likely due to the high demand from consumers, who are often unaware that date mussel fishery and trade is illegal, the high price of the resource and the weak law enforcement, particularly in the past (FAO, 2004; Katsanevakis et al., Reference Katsanevakis, Poursanidis, Issaris, Panou, Petza, Vassilopoulou, Chaldaiou and Sini2011; Muscogiuri and Belmonte, Reference Muscogiuri and Belmonte2007). To discourage this practice, it is certainly very important to continue information and educational campaigns aimed at warning that date mussel consumption is illegal, as well as ensuring continuity of control activities. In Italy, the fight against the harvesting of the species has contributed to the rarefaction of this illegal practice in recent years.
The use of ‘opportunistic’ methodologies typical of citizen science in this project to collect semi-quantitative data on the distribution of C. longispinus and S. latus in the pilot areas confirmed the effectiveness of this approach. The acquisition of catch data from professional fishermen enabled us to cover a greater bathymetric range than that generally frequented by recreational divers. The differences observed among sites in the number of sightings and catches were mainly due to an uneven sampling effort determined by the different level of participation to the project by the diving centres and professional fishermen contacted.
In the forthcoming monitoring programmes, it will be advisable to improve the level of standardisation and replicability of data collection by acquiring more detailed information on monitoring effort (e.g. the number of dives devoted to data collection and the number of divers involved, the number of hauls and the length of the net used by fishermen), and to include unprotected areas in the experimental design. To get reliable estimates of abundance of C. longispinus and S. latus, it will also be necessary to apply more rigorous data collection methods, such as visual censuses along transect (see Colletti et al., Reference Colletti, Oliveira, Bernardi and Cerrano2019).
Overexploitation is the major threat for S. latus throughout most of its range (Butler et al., Reference Butler, MacDiarmid and Cockcroft2011). In Italy this species has been subject to uncontrolled fishing by trammel nets and underwater fishing for decades (Pessani and Mura, Reference Pessani, Mura, Lavalli and Spanier2007). Some actions to halt the population decline of slipper lobsters have been taken by some Mediterranean countries, such as Spain and Italy, which have banned its fishing by recreational fishermen, and France, where the ban also affects professional fishermen (Lloret et al., Reference Lloret, Biton-Porsmoguer, Carreño, Di Franco, Sahyoun, Melià, Claudet, Sève, Ligas, Belharet, Calò, Carbonara, Coll, Corrales, Lembo, Sartor, Bitetto, Vilas, Piroddi, Prato, Charbonnel, Bretton, Hartmann, Prats and Font2020). In the Mediterranean Sea, another threat to S. latus is represented by the entanglement of individuals in ghost nets (Perroca et al., Reference Perroca, Giarrizzo, Azzurro, Rodrigues-Filho, Silva, Arcifa and Azevedo-Santos2024).
There are no reports in the literature on the intentional harvesting of individuals of C. longispinus, whereas bycatch from trawling activities is reported as one of the major impacts on the species in Spanish seas (Guallart and Templado, Reference Guallart, Templado and Aa2012).
Conclusions
The results of the monitoring activities presented here not only provide new insight into the presence and distribution of five invertebrate species of European Community interest but also highlight their vulnerability. The most critical situation, due to very different causes, concerns the two endemic species P. ferruginea and Pinna nobilis, whose small populations are currently confined to very few areas. The fight against the illegal harvesting of L. lithophaga has made the conservation status of this species less concern, even though this practice persists in some coastal areas. For species such as S. latus, for which the Habitats Directive requires regulated harvesting, it is important to define and adopt common management measures for Mediterranean fisheries and to intensify monitoring and control activities on catches.
Finally, we wish to emphasise the importance of intensifying communication and awareness-raising activities, to make citizens more aware of the European and national regulations and of the importance of preserving threatened and endangered species.
Acknowledgements
We would like to thank the staff of the Regional Agencies for Environmental Protection (ARPAs) and the marine protected areas (MPAs) for their professional collaboration in collecting the data. Special thanks go to our colleagues Massimo Dalù, Valentina Pantano, Gianluca Franceschini and Camilla Antonini for their support in field activities. We are grateful to the two anonymous referees for their helpful suggestions.
Author contributions
All authors contributed to the study’s conception and design. Material preparation, data collection and analysis were performed by Gabriele La Mesa and Margherita Zingaro. The first draft of the manuscript was written by Gabriele La Mesa and all authors provided commentson previous versions of the manuscript. All authors read and approved the final manuscript.
Funding
This study was funded by the Italian Ministry of the Ecological Transition within the framework of the monitoring activities under the ‘Accordo MITE-ISPRA per l’attuazione della Direttiva Quadro sulla Strategia per l’Ambiente Marino (Direttiva 2008/56/CE) e la Direttiva Habitat (Direttiva 92/43/CEE) a mare,’ signed on December 202.
Competing interests
The authors have no conflicts of interest to declare that are relevant to the content of this article.
