Italy’s Contribution to Artificial Reef Research: A Comprehensive Review (1970–2025)

Abstract

Italy represents one of the most prominent European countries in artificial reefs (ARs) research, with over 50 years of history and the construction of the second artificial reef in Europe designed according to scientific criteria. A review of 560 documents on Italian artificial reefs (ARs) from 1970s to 2025—including 404 scientific papers and 156 gray literature sources—together with an in-depth web-search allowed the identification of 118 artificial reefs deployed in the Italian seas. Concrete represents the most used material for AR construction, due to its durability over time, and ductility to build modules of different shapes and dimensions. More than 70% of the Italian ARs are made of concrete utilized alone or with other associated materials. Habitat protection and finfish enhancement have been the main scopes for AR deployment. Most scientific papers on Italian artificial reefs refer to the zoobenthic communities settled on the manmade substrates or living in the surrounding soft bottom, finfish assemblage, ecology, and general themes, such as history and management of the reefs. Recommendations include the need for a multidisciplinary panel of experts to comprehensively assess the environmental, biological, and socio-economic characteristics of an area selected for a new AR, and for development of eco-designed structures.

1. Introduction

Artificial reefs (ARs) are interventions of ecological engineering consisting of the deliberate placement of submerged (or partly exposed to tides) natural or manmade structures on the seabed to mimic some functions of natural reefs to protect, concentrate and/or enhance populations of marine life [1,2,3,4].

Objectives of an AR may also include promotion of research, recreational opportunities, educational use, sustainable fisheries and aquaculture [5].

The conservation and enhancement of marine living resources via the deployment of ARs can be achieved through the protection or restoration of ecologically sensitive habitats—such as coastal zones, spawning and nursery grounds, and seagrass meadows—and the establishment of novel artificial habitats that facilitate the settlement and recruitment of larval and juvenile stages. These early life stages, while naturally present in the marine environment, are often lost due to the limited availability of suitable substrates and shelters. These types of interventions align with the concept of Nature-Based Solutions (NBSs), a framework developed over the past decade that integrates ecological engineering principles to address global environmental and societal challenges. NBSs aim to protect, sustainably manage, and restore natural or modified ecosystems, while simultaneously delivering benefits for human well-being and biodiversity conservation [6,7,8]. In fact, Barot et al. (2012) [9] argue that the primary objective of ecological engineering is to develop sustainable practices informed by ecological principles, with the purpose of protecting, restoring, or transforming ecological systems to enhance the provision, quality, and long-term viability of the ecosystem services they offer. Alternatively, it involves the construction of novel ecological systems capable of delivering comparable services to those traditionally achieved through conventional engineering approaches that rely on non-renewable resources.

Depending on the scope and the structural complexity of an AR, its deployment can be related to at least one of the NBS categories identified by Riisager-Simonsen et al. (2022) [8], such as Type B—NBSs that improve multi-functionality of managed marine ecosystems—or Type C—NBSs which provide novel, restored or deliberately designed artificial marine ecosystems—based on the required level of biodiversity and ecosystems engineering involved and the level of enhancement of ecosystem services achievable by the NBS.

Although ecological engineering and NBSs are rather newly developed concepts, the use of ARs to enhance aquatic resources around the world dates back several centuries [10,11]. A similar historical trajectory occurred in Italian waters and, more broadly, across the Mediterranean Sea, where the earliest ARs were unintentionally created approximately 3000 years ago as a consequence of traditional tuna fishing practices [12]. Nevertheless, the modern concept and intentional deployment of ARs in Italy only began in the 1970s.

The Italian peninsula, situated at the center of the northern Mediterranean basin, features approximately 8300 km of coastline. The coastal areas are densely populated, with around 30% of citizens permanently living in urban settlements spread on a territory of 43,000 km², corresponding to around 13% of the overall national territory [13,14]. The high degree of coastal urbanization, coupled with intensive economic activities—such as maritime transport, fisheries, aquaculture, tourism, and gas extraction—has resulted in the degradation of natural marine coastal ecosystems, the overexploitation of living marine resources, and the emergence of numerous inter- and intra-sectoral conflicts over space and resource use.

In this context, ARs have been deployed in order to minimize conflicts, protect and increase marine resources and support sustainable fishing and aquaculture activities (i.e., small-scale fisheries, extensive shellfish culture).

One hundred and eighteen ARs have been deployed since the 1970s along the Italian coasts, and there is still a growing interest to plan and develop innovative AR projects related to sustainable tourism, coastal management and restoration in the context of the Integrated Coastal Zone Management and Maritime Spatial Planning policies, according with the Blue Growth principles.

AR construction in the Italian seas has been sustained on time by a range of associated research activities concerning all the main abiotic and biotic components of the marine ecosystems.

Given Italy’s prominent role in the deployment of ARs in the Mediterranean and the increasing significance of this practice over time, this paper provides a comprehensive overview of the development of ARs in this country, with particular focus on their evolution in technical design, functional objectives, and the related scientific literature.

2. Materials and Methods

2.1. Collection and Analysis of Published Data

A systematic literature search was carried out to identify both scientific and gray literature on Italian ARs. A total of 560 documents were found, 404 of which were scientific papers. All the gray and scientific papers are listed in Table S1 of the Supplementary Materials.

Scientific literature was searched through the consultation of Elsevier, Taylor and Francis, Rosenstiel School of Marine and Atmospheric Science (University of Miami), MDPI, SCIELO and CSIRO journals, some of which published special editions on ARs research, as well as through SCOPUS, Web of Science and Google Scholar. National, scientific journals were also checked, as well as conference proceedings, most of them stored in the CNR-IRBIM archives. The included publications are available online or via interlibrary loan; duplicate publications were removed and treated as a single document.

It was not possible to use keywords to classify the 404 scientific papers because, until the 1990s, most scientific journals did not include a “keyword” section in the published articles.

So, the main treated topics addressed by Italian scientists involved in the research on ARs have been considered. Topics were assigned based on the content of each individual paper, with a maximum of four topics identified and attributed per publication.

The gray literature included technical reports (only the final reports produced at the conclusion of research programs were considered and counted), as well as degree and PhD theses, and magazine articles. Although gray literature can contain a substantial amount of valuable information, it is often difficult to access, which risks underestimation. Therefore, while this type of document was used to gather technical and/or biological information on ARs, only scientific literature was considered for the analysis of Italy’s scientific output.

2.2. Census of ARs

As explained above, both scientific and gray literature were reviewed to compile a comprehensive census of ARs in Italy. Information was also taken from the new database on Adriatic ARs implemented within the framework of the Italy–Croatia Interreg project “Innovative exploitation of Adriatic Reefs in order to strengthen blue economy—Adrireef” [15]; furthermore, an in-depth web-search was also carried out. The websites consulted belong to research institutes and universities, national, regional or local institutions, diving centers, environmental associations and enterprises, etc.

The above search made it possible to update the census of the Italian ARs up to April 2025. Year of deployment, materials used for reef construction and main scopes of the ARs were examined.

It is important to clarify that for this study, only ARs falling within the standard definition provided by Guidelines for the placement at sea of matter for purposes other than the mere disposal (construction of artificial reefs) [1], the Guidelines for the Placement of Artificial Reefs [16], the Assessment of construction or placement of artificial reefs [2], the Guidelines and management practices for artificial reef siting, use, construction, and anchoring in Southeast Florida [3] and the practical guidelines for the use of artificial reefs in the Mediterranean and Black Sea [4] were considered, thereby excluding fish aggregating devices (FADs), breakwaters, underwater cables, accidentally sunken wrecks, offshore platforms, and similar structures.

3. Results and Discussion

3.1. Literature Review

The topics of the 404 scientific papers written by Italian researchers since the 1970s are reported in Figure 1 and

Table 1. Themes covered by the scientific papers on Italian artificial reefs in the different decades. The total number of scientific papers per decade is also reported.

Topic	1970s	1980s	1990s	2000s	2010s	2020s	Total
Algal population		3	13	12	1	2	31
Benthic community	9	36	35	26	15	3	124
Ecology	8	27	28	5	4	2	74
Environmental monitoring			3	5	3	1	12
Finfish population	3	23	45	23	16	1	111
Fishery		9	12	7	7		35
General 1	1	23	15	12	9	3	63
Mariculture		9	12	2		4	27
Mollusks	4	14	6	3			27
Shellfish culture		6	6	1		3	16
Technology		1	6	12	8	3	30
Water column	1	3	1	5	2		12
Total number of scientific papers	13	79	147	92	56	12	404

Note: ¹ General: ARs history, general considerations, etc.

. In general, over these 55 years of scientific production, the most frequently addressed subject by Italian researchers has been the benthic community—found 124 times, followed by finfish population (111 times), ecology (74 times), and general discussions on the installation, economic role of ARs, etc. (63 times).

3.1.1. 1970s and 1980s: Investigations into the Ecological and Biological Role of ARs

Relini and Orsi Relini were the first Italian authors, writing a paper in 1971 on the Varazze AR, the first Italian AR deployed [17]. Due to the scarce experience on ARs and the limited number of involved researchers, the 1970s represent the decade with the lowest number of scientific papers in Italy on ARs (13). Although almost exclusively written in Italian [17,18,19,20,21,22,23,24,25,26,27,28] and mostly unavailable online, these documents represent the main, if not the only, source of information to reconstruct the history of the first ARs installed along the Italian coasts.

Ecology and zoobenthic communities settled on the artificial substrates were the main topics in that period. A plausible explanation is that, even though the high ecological potential of these artificial habitats was already well-known by Japanese and American experiences, ARs still represented an unexplored field in Italy and, more generally, in the Mediterranean Sea; in fact, before Varazze, only one AR had been deployed in France in 1968, the offshore Palavas-les-Flots [29]. Many studies had already been carried out in the 1960s on the zoobenthic communities settled on hard substrates of harbors or on artificial panels [30,31,32], but the deployment of 3D substrates not yet colonized represented a great opportunity for ecologists to understand the colonization processes from the earliest stages in different coastal environments (both in oligotrophic and eutrophic waters) and in relation to some variables (e.g., modules’ orientation and extension along the water column).

The interest towards ARs increased in the 1980s when the Italian scientific production reached 79 papers. In that decade, the main topics remained the zoobenthic colonization of the artificial substrates described in 36 publications; a significant increase has concerned the ecological role of ARs (27 publications) as well as the general information on the ARs’ use and finfish population (Table 1).

3.1.2. 1990s: The Debate on Attraction/Production and Possible Economic Outcomes of the ARs

Finfish population became the most important topic of the 147 papers written in the 1990s, also due to the well-known and still ongoing debate at international level on the role of ARs in terms of attraction and/or production [33,34,35]. This theme has been found in 45 papers focusing on fish assemblage and the trophic relationships between fish and artificial habitats. Consequently, fisheries associated with artificial reefs became a key focus of research, both in terms of catch rates and the promotion of sustainable fishing practices, such as small-scale artisanal fisheries. ARs were also seen as a means to support the equitable allocation of maritime space, with the resulting reduction in intra-sector conflict [36,37,38,39,40]. However, ecological aspects and zoobenthic communities remained among the priorities (28 and 35 papers treating these two topics, respectively), due to the internationally recognized Italian expertise in these fields.

In the 1990s, interest also grew in other topics, such as algal populations, a subject thoroughly explored by the University of Trieste, which focused on the colonization of manmade substrates in the Northern Adriatic and Ligurian Seas [41,42,43,44].

Several experiments were conducted on the potential use of ARs for mariculture and shellfish farming. This economic aspect was particularly addressed by the CNR-IRBIM of Ancona, which continued the experimentation on shellfish (Mytilus galloprovincialis, Ostrea edulis, Crassostrea gigas, and Pholas dactylus) and finfish culture (Sparus aurata and Homarus gammarus) that had already begun in the 1980s [45,46,47,48,49,50,51,52].

3.1.3. The 2000s–2020s: Old and New Interests

At the beginning of the new century, scientific production drastically decreased (92 scientific papers were found) despite the great number of new ARs deployed in that period as described below. This incongruity is likely linked to the decentralization of several political and management issues from the National Government to the Regional Authorities and the subsequent greater involvement of the Regional Agencies for the Environment and Research Cooperatives to carry out the multi-year monitoring required for AR deployment. These agencies and cooperatives primarily produce technical reports, which are typically distributed exclusively to relevant stakeholders and are not publicly available online.

However, benthic community and finfish population remained the primary research themes, also in the 2000s, being addressed in 26 and 23 publications, respectively [53,54,55,56,57,58,59,60,61,62]. In contrast, interest in ecology and mariculture and shellfish culture sharply declined, with publications on these topics decreasing by 82% and 87%, respectively, compared to the 1990s. During the same decade, “technology” became an important theme in the AR scientific production, due to the use of innovative acoustic systems, such as multibeam echosounders and other hydroacoustic techniques (stationary or mobile hydrophones) to assess changes in the seafloor around the artificial modules, analyze spatial arrangement and structural integrity and investigate fish behavior around the artificial modules [63,64,65,66,67].

Moreover, some overviews describing environmental features, research fields, uses and possible exploitation of ARs were produced by research teams operating in different Italian areas [12,68,69,70,71,72,73,74].

In the 2010s, the scientific production dropped further by about 39% from the previous period (56 scientific papers were found). Finfish population and zoobenthic communities still remained the most important topics [75,76,77,78,79,80,81], followed by technology and general discussions on ARs management, intra-sectorial interactions, and general overviews [82,83,84,85]. Notably, a comprehensive guideline for the use of ARs in the Mediterranean and Black Sea was produced by Italian authors in cooperation with European colleagues and released by FAO-GFCM [4].

Finally, during the first five years of the 2020s, only 17 papers were found, with no dominant theme clearly emerging among them.

3.2. Development of Italian ARs

The first, unintentional ARs in Italy date back to three millennia ago. At that time, tuna fishing was already a business in Sicily using huge nets called tonnare anchored in place by heavy rocks [86,87]. At the end of each fishing season, when the tonnare were recovered, the stones were left behind, and over the years, their deposition made new rocky habitats populated by benthic fauna and fish [12]. The fish were exploited by fishermen during the intervals between tuna fishing seasons; the improved yields from tonnare prompted the sinking of wrecks and boulders so that the setting up of refuges and attraction sites for fish became common practice. Similarly, new fishing grounds were realized by dumping the ruins of Greek temples during the construction of small harbors in the southern coast of Sicily, such as Porto Empedocle and Gela [12]. In north-eastern Sicily, other fish-attracting structures called Cannizzati were made with sandstone boulders used to anchor FADs [12,88].

The history of the “modern” ARs in Italy began in the 1970s, when initiatives and experiments were prompted by the requirement to actually manage and enhance coastal areas subject to inter- and intra-sector conflicts.

Since then, 118 ARs have been deployed along the Italian coasts (Figure 1): 49 ARs were constructed along the Adriatic coast, 33 in the Tyrrhenian Sea, 13 in the Ligurian Sea, 11 in the Ionian Sea, 10 in the Sicily Channel and 1 in the Sardinia Sea.

For four of these ARs, all are deployed in Sicily, one of which in the Tyrrhenian Sea (Cala Bianca), and three in the Sicily Channel (Capo San Marco, Porto Palo di Capo Passero, and Sciacca); no information on the materials used and/or the year of deployment could be found.

3.2.1. The 1970s: The Pioneering Phase

The first Italian AR was deployed in offshore Varazze (Ligurian Sea) in the 1970 by recreational fishermen without any scientific support [73,89]. One thousand and three hundred car bodies were sunk between 35 and 50 m depth to prevent trawling and improve recreational fishing in the area [90] (Figure 2, Figure 3 and Figure 4). The AR was augmented with 16 wooden barges in 1979.

Four years later (1974), the first scientifically planned AR was deployed by CNR-IRBIM (CNR-Istituto Ricerche sulla Pesca Marittima—IRPEM at that time) in the central Adriatic Sea, at 5.5 km offshore Porto Recanati (Marche Region) on a 13 m depth muddy seabed, with the aims of preventing trawling, repopulating the area with new life and developing new, sessile biomass, especially mussels and oysters [20,21,22,91,92,93]. The AR was composed by 3-layer pyramids 6 m high, each made of 14 concrete cubic blocks (2 × 2 × 2 m) called “IRPEM blocks”, which formed a central oasis of 0.03 km². Stone piles were placed among the pyramids to make the reef system continuous and two wooden vessels were sunk at the center of the oasis (Figure 5). In addition, the oasis was surrounded by a protective area (20 km²), where cubic blocks and other smaller anti-trawling devices were scattered [69].

The second experimental AR was deployed in 1978 in front of Miramare (Friuli Venezia Giulia Region, Northern Adriatic Sea). This small AR, covering an area of 180 m², was made of irregularly arranged concrete pipes on a 16 m depth muddy bottom [94] with the aim of protecting the area and favoring the settlement of new biomass [95] (Figure 3, Figure 4 and Figure 5).

One year later (1979), another small AR made of six wooden barges was deployed in front of Camogli (Ligurian Sea), between 20 and 40 m depth, but it was not studied in the following years [73].

Materials and Outcomes for 70s—These first experiences revealed that car bodies were not eco-friendly as they contained polluting substances, such as heavy metals in paints. Moreover, a high rate of corrosion of paints and metallic materials was observed [17]. making it difficult for sessile fauna to settle. These results were so negative that car bodies as material for ARs were banned in Italy, particularly because of pollution concerns [73]. Nevertheless, during a scientific conference held in Rome in 1981, Relini reported that “it was revealed that in August 1981, 700 car wrecks were sunk off the coast of Pozzallo (Sicily Channel) without any consultation with biologists” [96].

Wooden wrecks resulted in more suitable than car bodies for the recruitment of benthic organisms, more attractive for fish, and more effective in preventing illegal trawling due to their volume and weight, although subject to the action of boring and microbial organisms.

Instead, concrete appeared to be the most suitable material due to its resistance and eco-friendliness. The basic IRPEM block efficiently prevented illegal trawling thanks to its weight (13 tons); moreover, holes of different sizes and shapes provided habitat and shelters for marine biota, and the rough surfaces facilitated the settlement of sessile organisms.

3.2.2. The 1980s: Experimental and Expansion Phase

A total of 22 ARs were deployed in 1980s (Figure 2, Figure 3 and Figure 4). Some of them were installed by fishery associations as a result of the EC Regulations n. 2908/83 and n. 4028/86, with the financial contribution of the European Union (EU) and the scientific support of research institutes and universities, which also carried out scientific monitoring to evaluate the structural resistance and the biological colonization of the manmade modules. The other ones were experimental ARs.

Sicily was the region with the highest number of ARs deployed in the 1980s (six ARs), followed by Emilia Romagna, Liguria and Marche each one with four ARs (Figure 2). In some other regions, only one AR was deployed: along the Tyrrhenian coast of Calabria (Santa Eufemia Gulf AR) [97], Friuli Venezia Giulia (Aurisina AR) [98], Latium (Fregene AR) [99] and Apulia (in front of Ischitella, Adriatic Sea) [100] regions, all made of concrete modules, cubes and/or anti-trawling devices.

Sicily—In Sicily, the ARs were mainly deployed at depths between 10 and 30 m in different locations of the Gulf of Castellammare (NW coast of Sicily, Tyrrhenian Sea) and the Gulf of Patti (NE coast). Most of them were made of IRPEM blocks assembled to form three-layer pyramids and of anti-trawling structures named “torpedo”, which were prismatic concrete boulders armed with iron spikes. The first one (1981) was a small experimental AR in front of the Terrasini harbor where little concrete blocks (side: 1–1.4 m) with four 20 cm² tunnels in each face were used to form four pyramids; the other ones were broader and placed off Trappeto, Alcamo Marina, Balestrate and Patti.

Liguria—The Ligurian ARs were constructed in the Marconi Gulf (1980) and offshore Loano (1986), Spotorno and Ventimiglia (1989–1990) [73]. Except for the AR deployed in the Marconi Gulf in 1980, initially made of wooden barges and later enriched with concrete blocks, the other three artificial habitats were made of concrete modules of different shapes and dimensions. Loano, the most investigated Ligurian AR [71,90,101,102,103,104,105], covered a surface of around 3.5 km². Its central part was composed of 30 two-layer pyramids each made of five concrete IRPEM blocks of different sizes (2 × 2 × 2 m and 1.2 × 1.2 × 1.2 m). Surrounding this core, there was a protection buffer, where single blocks, armed with iron bars and hooks to prevent trawling, were scattered at depths ranging from 5 to 45 m [105]. In 1989, additional large blocks were added to reinforce the outer part of the reef. The primary objectives of this AR were to enhance halieutic resources and to protect and restore the local Posidonia meadow [73]. In contrast, the ARs off Spotorno and Ventimiglia were smaller and constructed with different materials, including steel piles to discourage illegal trawling, small open concrete blocks for benthic settlement, and large prefabricated cement modules called “Bonna”, inspired by French experience [106], and intended to attract pelagic species. Unfortunately, no data are currently available for these two ARs.

Marche Region—Along the coast of Marche Region (Adriatic Sea), two experimental and two professional ARs were constructed in 1980s, all designed by CNR-IRBIM. The first experimental reefs were deployed in the Portonovo bay (Conero Promontory) and offshore Senigallia (North of Ancona) in 1983 and 1987, respectively. “Portonovo 1” (Figure 6), a small AR deployed about 0.8 km offshore, consisted of four two-layer concrete pyramids (each built from five IRPEM blocks) of 4 m height, placed at the corners of a square, and spaced about 20–25 m apart. The top blocks of each pyramid were interconnected with steel wires to support suspended mussel and oyster culture. This small AR was investigated almost exclusively for shellfish culture [45,107,108,109], based on the excellent results obtained at the Porto Recanati AR (100 kg/m² of invertebrates settled on artificial modules, mainly mussels) [20]. The Senigallia AR was placed 2.8 km offshore on a sandy–muddy bottom at a depth of 12 m. It consisted of 29 concrete pyramids similar to those of “Portonovo 1”, and 12 concrete cages (5 × 6 × 4 m) for shellfish culture. Anti-trawling structures were scattered in the surroundings, covering a protection area of 2 km². Like the Loano AR in Liguria, the Senigallia AR resultingly became the most investigated in the Adriatic Sea and the site of several experimental trials [36,37,38,57,59,63,77,78,110,111,112].

In addition, two professional ARs were established in 1988 at the request of local fishermen’ associations. The extensive Falconara AR (north of Ancona) covered an area of 125 km², between 2.8 and 5.5 km offshore, and was made of 179 concrete structures called “stars” due to their shape and 350 IRPEM blocks scattered across the area. Its goals were finfish repopulation and protection of the coastal area from illegal trawling. The intensive, multi-purpose “Portonovo 2” AR (0.6 km offshore and 10 m depth) consisted of three oases, each made of 29 concrete two-layer pyramids and 12 concrete cages covering a total area of 0.02 km² (Figure 6). The reef was built to enhance finfish population, protect the surrounding natural rocky habitat, improve professional small-scale fishery and develop extensive shellfish culture.

Emilia Romagna—The four ARs deployed along the coast of Emilia Romagna were established between 1988 and 1989 at the request of local fishermen’s association with the scientific support of CNR-IRBIM.

Concrete pyramids and cages were utilized to realize three ARs (Porto Garibaldi 1, Rimini and Cattolica). “Porto Garibaldi 1” consisted of 72 pyramids and 24 concrete cages organized in four oases deployed at the corners of a square area with sides of about 500 m. Both Rimini and Cattolica ARs were larger than “Porto Garibaldi 1” and consisted of 118 pyramids and 48 cages organized in four oases (surface: 60 × 90 m each one) placed at a distance of about 200 m from each other [69,113].

The fourth AR in Emilia Romagna (“Porto Garibaldi 2”) covered a squared area of about 0.02 km² and was placed inside a protection area where 191 IRPEM blocks were scattered as anti-trawling structures. This reef consisted of 100 specially designed structures (4.5 × 4.5 × 4.5 m), each assembled from concrete panels and cylinders. However, these structures proved to be poorly resistant to sea storms. Indeed, within a year of deployment, some of them had already been destroyed and partially sunk into the soft seabed [69].

Friuli Venezia Giulia, Apulia, Latium, and Calabria—Four additional artificial reefs were deployed during the 1980s: two in the Adriatic Sea (Apulia and Friuli Venezia Giulia) and two in the Tyrrhenian Sea (Calabria and Latium) (Figure 3). All were constructed using concrete blocks, tetrapods, or other anti-trawling devices, primarily aimed at habitat protection and finfish enhancement.

Materials and Outcomes for 80s—Concrete, alone or associated with other materials, was the primary material utilized to construct the Italian ARs in 1980s (Figure 5). By the end of the decade, cement-stabilized coal ash, which had been successfully used in several non-Mediterranean countries (Taiwan, China, USA) [114,115,116,117], was experimentally tested in Italy. This material was deployed in the form of cubes at Loano (Ligurian sea) and Senigallia ARs (Northern Adriatic Sea). The coal ash turned out to be crumblier than concrete, and hence was not suitable for the construction of anti-trawling reefs; nevertheless, it appeared appropriate for the development and growth of benthic communities, even though more selective with respect to concrete [110,118,119]. Moreover, at Senigallia, it appeared suitable for the settlement of the boring bivalve P. dactylus (common piddock) [46,47,48], a very locally appreciated species due to its organoleptic characteristics. Since wild harvesting of common piddocks has been forbidden by Italian law since 1988 and by the EU regulation 1967/2006, due to its destructive impact on natural hard substrates, trials were carried out at Senigallia and, in 2000s, at Portonovo 1 reefs [120] to evaluate the use of coal ash for mariculture initiatives to be implemented under specific regulations and controls (e.g., a final certified product) with the aim of discouraging illegal harvesting and, at the same time, diversifying the Italian shellfish culture production.

About 85% of ARs deployed in the 1980s were multi-purpose ARs. The main aims were (a) to protect coastal spawning and nursery areas from illegal trawling at depth ≤ 50 m or within the 3 nautical miles (nm) boundary; (b) to create new ecosystems for repopulation of reef-dwelling finfish and invertebrates by deploying suitable structures able to provide refuges and available surfaces for larvae, juveniles and adults; and (c) to reduce conflicts for space and resources between small-scale fisheries, shellfish cultures and recreational activities [69,107]. Accordingly, the concept of “Marine Spatial Planning”—already known in some countries [121,122]—was starting to materialize in Italy as well.

3.2.3. 1990s: Diversification and Specialization

In the 1990s, a total of 18 ARs were deployed, half of them in Sicily, which resulted in the most productive region (Figure 2), followed by Latium (three ARs in different places of Ponza Island) and Liguria (two; Lavagna and Alassio) [73,123]. One AR was realized in Emilia Romagna (“Paguro” rig) [124], one in Friuli Venezia Giulia (Dosso di S. Croce) [125,126], one in Apulia (Cheradi Islands, Ionian Sea) [127] and one in Campania [128].

Most of the reefs, representing 88% (16) of those deployed in this decade, were made of concrete modules (Figure 4). Only one reef (Dosso di S. Croce, Friuli Venezia Giulia) was constructed utilizing concrete modules of different shapes together with iron, as some modules were arranged in pyramids and others provided with anti-trawling poles or polyethylene tubes.

Most of the ARs installed in the 1990s were experimental and mainly aimed to protect environment and enhance finfish population (Figure 3).

Rig-to-reef in Italy—The 1990s saw the emergence of Italy’s only “rig-to-reef” example: the “Paguro” rig. Originally a drilling platform that accidentally sank in 1965, in a short time, Paguro hosted a rich fauna, presumably reflecting a high structural complexity [124] and it was voluntarily implemented in 1990–1991 (and then in 1999–2000) with other decommissioned, steel structures, so as to form a rig-to-reef. The ecological and biological importance of the Paguro rig is recognized at both a national and an international level, being declared a Biological Protection Area in 1995 (Ministry Decree 21 July 1995), a Site of Community Importance in 2012 (SCI code IT4070026) and, finally, a Special Area of Conservation in 2019 (Ministry Decree 13 March 2019). The Paguro rig has also been used to promote diving.

3.2.4. 2000s: Scaling up and Multi-Functionality

The largest number of ARs was deployed in the first decade of the new millennium, with a total of 53 installations. Of these, 28 were placed along the Adriatic coast (Figure 2), representing the highest concentration in a single marine area. Additionally, 15 ARs were installed in the Tyrrhenian Sea, 7 in the Ionian Sea, and 3 in the Ligurian Sea.

Several of these ARs are medium- or large-scale reefs and were installed with the financial contribution of the EU. Some of the new ARs (e.g., ARs of Porto Recanati—Porto Potenza, Pedaso—Cupra Marittima, Pescara, Torre del Cerrano in the Adriatic Sea; ARs of Piombino—Punta Ala, Marina di Cecina—Marina Castagneto in the Tyrrhenian Sea) were deployed at a 3 nm boundary offshore to protect the coastal area from illegal trawling and enrich benthic and fish communities (Figure 7). They were generally arranged in a rectangular shape with the longest side parallel to the coast. The perimetral modules were heavy structures for anti-trawling purposes, positioned in such a way to impede the passage of trawlers towards the inshore area, while the central oasis is made of modules, often of different shapes, to encourage the larval settlement of sessile fauna and to allow marine life to take possession of different habitats [79,80,129].

Tourism integration—In the 2000s, there was an increasing interest in the use of ARs to promote sustainable tourism. As an example, the Polignano AR (Apulia Region, southern Adriatic Sea), was deployed in 2005 to enhance small-scale fishery and diving tourism, but the initiative has not been well-promoted and only a few expert divers know of it. Nevertheless, the AR, covering an area of 0.2 km², played a very important role in protecting the surrounding coralligenous biocenosis and Posidonia meadows [130].

Another example is the AR deployed on offshore Talamone—Porto Santo Stefano (Tuscany; Tyrrhenian Sea), realized in 2006 by the local authorities with the EU contribution to impede illegal trawling, utilizing concrete blocks armed with iron bars. In 2018, a private association promoted the project “La casa dei pesci” (“The fish house”), aiming to protect the sea through art and improve the local tourist offerings. A network of artists created sculptures that were placed on the seabed inside the AR, becoming an attraction for divers and fishing tourists, and furthermore, obstacles against illegal trawling.

Design improvements—Most ARs deployed in this decade were still built with concrete (Figure 4), utilized to construct modules of different shapes and dimensions. Nevertheless, Tecnoreef^® modules, made of sea-friendly reinforced concrete slabs and already tested in some previously installed ARs (e.g., Dosso di Santa Croce and Senigallia ARs, Adriatic Sea), became the second most-used structures. The Tecnoreef^® slabs might have different shapes and sizes, and they were assembled to form pyramids of different dimensions. The main scopes of these structures were finfish and habitat enhancement (Figure 4) and they were often associated with heavier modules made of traditional concrete which were more suitable for habitat protection (e.g., ARs of Scardovari, Casteldimezzo—Monte Castellaro, Pedaso—Cupra Marittima, Northern and Central Adriatic Sea) [75,80,131,132]. Other ARs exclusively made of Tecnoreef^® modules (e.g., Trieste and Ravenna ARs in the northern Adriatic Sea; Riomaggiore, Corniglia ARs in the Ligurian Sea) were aimed to increase fish population and, more generally, marine life.

3.2.5. 2010s: Eco-Tourism and Innovation

In the 2010s, seven ARs were installed in the Adriatic Sea, one in the Ionian Sea (Apulia), one in the Sardinian Sea, and one in the Ligurian Sea (Figure 2). The use of ARs for recreational activities became the scope of about 20% of the ARs deployed (Figure 3). Among them, the Bibione AR (Veneto, Adriatic Sea) was deployed in 2014 and completed in 2018 due to bureaucratic problems. Made of concrete modules of various shapes and arrangements, this AR was managed by an ONLUS (non-profit organization of social utility) association with the aim of protecting the natural habitat, repopulation, shellfish culture and, at the same time, promoting diving and tourism activities.

3.2.6. The 2020s: New-Generation ARs

Finally, six new ARs have been deployed in the first 5 years of the 2020s (Figure 2). The first one, installed in 2020 in offshore Torvaianica (Latium, Tyrrhenian Sea), was made of concrete shafts, concrete tubes and clay bricks.

The second one, deployed in offshore Capo Peloro in the NE Sicily (Tyrrhenian Sea) in February 2021, was made of Tecnoreef^® pyramids and anti-trawling concrete structures.

Two other ARs made of concrete modules have been deployed in the Tyrrhenian Sea in front of Budoni (north-east Sardinia; 2022) and along the coast of Belvedere Marittimo (Calabria; 2023).

The goals of these four artificial habitats are protection against illegal trawling and finfish enhancement (Figure 3). The fifth AR, deployed in offshore Riccione in 2025 (Emilia Romagna Region, Adriatic Sea), is made of specific and innovative concrete modules called “Wmesh”, and aimed to counter coastal erosion and promote marine biodiversity.

The latest project is currently being carried out off the coast of Ventimiglia (Ligurian Sea), thanks to funding from the National Recovery and Resilience Plan, and it involves the construction of an AR specifically designed to create surfable waves.

4. Conclusions

In this study, a systematic literature search of scientific publications and gray literature provided an overview of 118 artificial reefs deployed in Italian waters since the 1970s, describing how their characteristics—such as location, materials, and purpose—have varied over time and across regions.

Italy is one of the most important European countries in terms of artificial reef development and has cultivated a wealth of expertise on the topic from biological, ecological, and engineering perspectives. For this reason, it was deemed important to provide detailed information on the development of this crucial tool for the sustainable management of maritime spaces.

In spite of some initial scepticisms on the role of ARs [133], experts in ecology, fishery and many other disciplines worked over the years to obtain valid and remarkable results from a scientific point of view. Nowadays, Italian research on artificial reefs is internationally recognized, and Italian scientists are sought after not only in Europe but worldwide for their expertise. Starting from only two regions in the 1970s, ARs are now deployed along almost the entire Italian coastline, with only a few exceptions. It is likely that some initiatives have gone unnoticed, as they may have only been advertised online or described in technical reports and other hard-to-access gray literature.

In this context, there is a risk that such installations may be implemented without involving a multidisciplinary panel of experts to comprehensively assess the environmental, biological, and socio-economic characteristics of the target area. Furthermore, there may be a lack of rigorous environmental monitoring, both prior to AR deployment and over time, to evaluate possible short- and long-term impacts.

Despite this well-established expertise in the field of ARs, the authors’ opinion is that in Italy, there are still some limitations. For instance, the implementation of eco-designed structures remains limited in spite of the number of infrastructures such as port quay walls and similar marine developments. Eco-design refers to the strategic incorporation of artificial microhabitats that support key ecological functions—including shelter, reproduction, spawning, and feeding—targeted at specific species and life stages [134,135].

Another aspect that has yet to take hold in Italy is the “rig-to-reef” concept. The benefits to fisheries from offshore platforms and their role as artificial reefs have been fully recognized since the 1970s [136,137]. Apart from the Paguro reef described above—and despite the large number of offshore platforms, particularly in the Adriatic Sea, many of which are approaching the end of their productive life—there are still difficulties, especially from oil companies, in recognizing these structures as opportunities to enhance the marine environment, even though numerous studies in Italy have demonstrated their potential since the 1970s [138,139,140,141].

The scientific literature used for the present overview may also be underestimated due to the difficulty in retrieving older publications, many of which were published exclusively in conference proceedings or national scientific journals without accessible online versions.

On the other hand, we believe that the value of this review lies precisely in having sought out these older scientific works, which risk being lost along with the numerous valuable pieces of information they contain.

Finally, the bibliographic survey conducted highlights how scientific knowledge on the potential of artificial reefs (ARs) has grown over the years, allowing the creation of increasingly complex artificial habitats in line with environmental and socio-economic needs.