EDP Sciences logo
Submit your paper
Sciengine logo
Search
Menu
All issues Volume 39 (2026) Aquat. Living Resour., 39 (2026) 24 Full HTML
Issue
Aquat. Living Resour.
Volume 39, 2026
Special Issue - Interdisciplinary issues on Manila and European clams in their socio-ecosystems
Article Number 24
Number of page(s) 16
DOI https://doi.org/10.1051/alr/2026020
Published online 22 July 2026

© O. Harbaoui et al., Published by EDP Sciences, 2026

Licence Creative CommonsThis is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

1 Introduction

Shellfish production has traditionally been restricted to coastal lagoons. However, over the past decade, these environments have become increasingly vulnerable due to their shallow depth and limited water renewal, a situation further exacerbated under climate change scenarios (Smaal, 2019; IPCC et al., 2023). These sensitive ecosystems are now exposed to multiple stressors, including repeated episodes of mass bivalve mortalities (McFarland et al., 2016; Tan and Zheng, 2020), outbreaks of infectious diseases (Asplund et al., 2014; Williams et al., 2014), delayed growth and development and shell dissolution associated with ocean acidification (Barton et al., 2012; Yang et al., 2017). These impacts are further intensified by the increasing frequency and intensity of marine heatwaves, which directly affect mollusks-highly sensitive and vulnerable organisms-including mussels, oysters, and clams (Rodrigues et al., 2015).

To address these challenges, offshore aquaculture has emerged as a promising strategy to mitigate bivalve mortality events, particularly during summer periods characterized by elevated water temperatures in coastal lagoons (Mille and Blachier, 2009; Komatsu et al., 2017; Wang et al., 2022). In the Mediterranean Sea, offshore aquaculture has been successfully applied to major shellfish species such as the Pacific oyster Crassostrea gigas and the Mediterranean mussel Mytilus galloprovincialis (Buck et al., 2017; Mascorda Cabre et al., 2021; Clawson et al., 2022). Offshore systems offer stronger water exchange, higher oxygenation, improved water quality, and enhanced nutrients availability compared with coastal environments-key factors supporting bivalve growth and survival in high-energy offshore conditions.

In this context, offshore aquaculture is increasingly considered as an alternative for bivalve storage and grow-out during critical warm periods, providing a strategic solution to reduce summer mortality risks associated with lagoon confinement.

Beyond growth and survival benefits, offshore aquaculture development has increasingly emphasized sustainable and environmentally friendly production systems that integrate ecological and socio-economic dimensions (Sanz-Lazaro and Sanchez-Jerez, 2020). Integrated multi-trophic aquaculture (IMTA) represents an innovative approach that promotes sustainable aquaculture development while enhancing ecosystem services and supporting local fishing communities (Papageorgiou et al., 2023). IMTA systems are based on the co-culture of species occupying different trophic niches at the same production site (Troell et al., 2009). Within this framework, bivalves, as filter-feeding organisms, are considered ideal bio-extractive components for the implementation of IMTA systems in offshore environments (Boyd, 2023; Chopin, 2013).

In Tunisia, Monastir Bay constitutes one of the country’s principal offshore aquaculture production areas, with an annual production of approximately 18.430 tons and hosting eleven offshore aquafarms (DGPA, 2024). The Tunisian shellfish sector is largely supported by the European clam R. decussatus, which represents 90% of the national production (Gharbi et al., 2023). This species is predominantly distributed in the Gulf of Gabès, where production still relies heavily on wild harvesting activities, highlighting both its bioecological importance as a filter feeder that contributes to water quality improvement through the filtration of suspended particulate matter and its high commercial value (Matias et al., 2009; Azirar et al., 2024). In contrast, shellfish production in the Bizerte lagoon is primarily based on the Pacific oyster Crassostrea gigas and the Mediterranean mussel Mytilus galloprovincialis (Turki et al., 2014). In fact, clam harvesting represents a major socio-economic activity and remains one of the most widespread fisheries in Tunisia, directly involving approximately 8.000 people; A substantial proportion of the production is exported to European markets, particularly Italy, Spain and France. In addition, these activities provide essential economic support to vulnerable coastal communities, especially women engaged in clam harvesting (Gharbi et al., 2023).

However, over the last two decades, European clam production has undergone a dramatic decline, decreasing by approximately 95%, with production dropping to only 84 tons during the 2019–2020 season (Gharbi et al., 2023).

To mitigate this decline and ensure the preservation of both spat and seed resources, aquaculture may represent an effective solution. In particular, offshore aquaculture could be considered a key management strategy to enhance production and promote long term sustainability.

In this context, the present study aimed, for the first time, to evaluate the feasibility of rearing hatchery-produced European clams R. decussatus in suspended lantern nets within an existing offshore longline structure originally installed for the cultivation of the mediterranean mussel Mytilus galloprovincialis, as part of an Integrated multi-trophic Aquaculture (IMTA) system under open-sea conditions in Monastir Bay, Tunisia. This approach was designed to assess the growth performance of clams reared in a longline system located in proximity to fish cages and to evaluate the suitability of suspended offshore culture for R. decussatus during both the pre-fattening and fattening phases.

Moreover, the present study is consistent with the Euro-Mediterranean research agenda outlined by Riquet et al. (2026), which emphasizes the need for a multidisciplinary network to standardize methodologies, improve data sharing, and strengthen science-based approaches to clam conservation and fisheries management. The decline of Ruditapes decussatus in Tunisia reflects trends reported from several European production areas, highlighting the need for coordinated research efforts and the development of innovative aquaculture strategies.

2 Materials and methods

2.1 Study area

This study was conducted over a 316-day period, from June 2023 to May 2024 in Monastir Bay, Tunisia. Experiments were performed on an offshore aquaculture farm rearing European sea bass Dicentrarchus labrax and gilthead sea bream Sparus aurata located between 35°47’N 35°37’N, 10°45’E 11°50’E (Figs. 1B–1C), which served as the host site for the implementation of the innovative IMTA system.

Thumbnail: Fig. 1 Refer to the following caption and surrounding text. Fig. 1

A: The geographic location of the study area in Tunisia; B: The experimental site located in Monastir Bay TTF farm (35°47’N 35°37’N, 10°45’E 11°50’E), C: Finfish cage of sea bass Dicentrarchus labrax and sea bream Sparus aurata with IMTA longline. Scales bars: A: 150km; B: 6,5km; C: 0, 2km.Source Esri, Maxar, Earthstar Geographics and GIS User Community.

2.2 Experimental design

This experiment was carried out using a longline structure was originally installed at 6 m depth, located 1.1 km from the fish cages, primarily for mussel Mytilus galloprovincialis rearing. The longline measured 150 m in length and was anchored by seven concrete ballasts (1 ton each) positioned on the seabed at 30 m depth, each attached to 330-liter surface floats to ensure structural stability.

Taking advantage of this pre-existing infrastructure, the present study aimed to assess the feasibility of rearing hatchery-produced European clam R. decussatus within the IMTA system. A single cohort of clam seed was artificially produced at the experimental bivalve hatchery of the National Institute of Marine Sciences and Technology (INSTM), Monastir, Tunisia, following the protocol described by Medhioub et al. (2017). The cohort was subsequently monitored throughout the entire 316-day experimental period, from June 2023 to May 2024.

Spawning was carried out in June 2022, followed by larval, post-larval and pre-fattening rearing phases. Two lantern nets (Lantern 1: L1; Lantern 2: L2) were deployed alongside a mussel longline system. A total of 1.219 twelve-month-old clams were used for the pre-fattening and fattening trials (Tab. 1). Clams seed were assigned to two experimental groups according to size class : the pre-fattening group included individuals with shell length: <13.28 ± 1.52 mm and weight <0.58 ± 0.24 g, whereas the fattening group consisted of individuals with shell lengths >15.90 ± 1.53 mm and weights >2.02± 0.37 g. Each lantern net consisted of eight stages, with stages 1–2 allocated to the pre-fattening phase, and stages 6–7 allocated to the fattening phase (Fig. 2D). Each size class was represented in duplicate (Tab. 1).

Subsequently, clams were initially placed in 2 mm mesh traps (Fig. 2B) and distributed into suspended lanterns made of a 4–5 mm mesh net, measuring 2 m in length and 40 cm in diameter (Fig. 2C). In June 2023, clam seed were transferred under temperature conditions of 7 °C to the study site for IMTA trial. Clam lanterns were therefore deployed alongside the mussel rearing structures already in place.

The IMTA system was designed to cultivate multiple species occupying different trophic levels at the same site of production site allowing the waste or excess feed of one species to serve as a resource for another. Fed species (finfish: sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) were combined with filter-feeding species such as oysters (Crassostrea gigas) and mussels (Mytilus galloprovincialis); deposit-feeding species such as sea cucumbers (Holothuria tubulosa et Holothuria polii); and inorganic extractive species such as algae (Gracilaria gracilis) (Fig. 3).

All species were reared on the same longline system. Regarding the rearing structures, mussels were reared in nylon mesh bags, oysters were cultivated in suspended lanterns and on ropes. At the same time, sea cucumbers were maintained in suspended double-net trays, and macroalgae were cultured in lantern systems (Fig. 3).

Thumbnail: Fig. 2 Refer to the following caption and surrounding text. Fig. 2

(A) Illustration of two sizes of clams: pre-fattening and fattening phases; (B) placement of clams in 2 mm mesh traps; (C) the distribution of clams spat inside suspended lantern consisted of 8 stages; (D) the distribution of the pre-fattening group (stage 1 and 2) (shell length: <13.28 ±1.52 mm) and for the fattening group (stage 6 and 7) (shell length: >15.90 ± 1.53 mm) (E) the placement of lanterns at the IMTA longline.
Table 1

Shell length (mean ± SD, mm) of duplicate per size class during the pre-fattening and fattening phases and number of individuals from June 2023 to May 2024. Inter-replicate Student's t-test P-values, pooled means and between-date comparisons.

Thumbnail: Fig. 3 Refer to the following caption and surrounding text. Fig. 3

Experimental IMTA systems. (1) mussel nylon bags, (2) oyster ropes, (3) clams suspended lanterns, (4) oyster suspended lanterns, (5) sea cucumber experimental suspended double-net trays, (6) ballast concrete, (7) macroalgae suspended lanterns, (8) second buoys, (9) principal buoys. L1: Lanterne1; L2: Lanterne 2.

2.3 Rearing monitoring and sampling

Once deployed, the suspended pre-fattening structures required constant monitoring and regular cleaning to ensure strong water exchange through the mesh of the nets. Continuous monitoring was conducted every two months to maintain optimal rearing conditions. This procedure was carried out from a vessel equipped with a steel arm and winch, allowing the attachment and retrieval of the suspended structures on board. Divers were employed to detach the lanterns from the bottom underwater line. During the bimonthly monitoring operations, lanterns were replaced to remove biofouling and trophic competitors such as Pinctada radiata, which can impede nutrient and oxygen availability necessary for clam growth.

Mortalities were also assessed in situ by removing open clam shells. The mortality rate is determined according to the equation:

Mortality  ( % )   =   [ ( n i − n f )   / ( n i + n f ) ]   ×  1 00 Mathematical equation

Survival rate: the survival rate (SR) was evaluated according to the equation:

SR  ( % )   =   [ ( n f /  n i ) ]   ×  1 00 Mathematical equation

Where ni the number of clam specimens at the beginning of the experiment; nf the number of clam specimens retrieved at the end of the experiment.

2.4 Biometry measurement

Every four months, lanterns were collected by scuba divers then transported to the experimental hatchery, where they were maintained in raceways with raw seawater (salinity: 42; temperature: 20 ± 1 °C; dissolved oxygen 8.09 mg L−1; and pH 8.04) for 72 h. At each sampling date (June 2023 and May 2024), 20 clams were randomly sampled from each duplicate lantern per size class. Clams were then measured for shell length and weight. Shell length was determined to the nearest 0.01 mm using a Vernier caliper (KS TOLLS®), while weight was measured to the nearest 0.01g using an electronic balance (KERN PCB®).

Length Growth rate = (L1−L0)/d, where L1 is the length (mm) at time 1, L0 is the length (mm) at time 0, and d is the number of days.

Weight Growth rate = (W1−W0)/d, where W1 is the Weight (g) at time 1, W0 is the Weight (g) at time 0, and d is the number of days.

Length gain is determined as follows: L2−L1

Weight gain is determined as follows: W2−W1

Where L1 and L2 and W1 and W2 are the shell length and weight at the beginning and the end of the experiment, respectively.

Condition Index CI To calculate the CI index 15 specimens were randomly sampled. Meat and shells of each specimen were weighed and dried in a Memmert® at 60 °C for 24 h. The CI was then calculated as follows:

CI  ( % )   =   [ dry weight of soft meat  ( g )   /  dry weight of shell  ( g ) ] × 1 00. Mathematical equation

Environmental parameters, including temperature, dissolved oxygen (DO), salinity, and chlorophyll-a were obtained from the Copernicus Marine Service (CMS). For this study, data were downloaded using the “My Ocean Viewer” platform provided by the Copernicus Marine Service (CMS). Daily interpolated concentration of surface chlorophyll-a and dissolved oxygen were retrieved for the period from June 2023 to July 2025 (CMEMS, 2025, last access in Novembre 2023). In addition, daily interpolated surface temperature and salinity data for the same period i.e. June 2023 to July 2025 were also downloaded at the time of access in November 2020 (CMEMS, 2025, last access in Novembre 2024). All datasets were exported in CSV format and processed using Microsoft Excel® software.

2.5 Data analysis

All statistical analyses were performed using SPSS® Statistics 27 software. Growth performance analyses (shell length and weight) were conducted in duplicate for each size class. Prior to analysis, data were tested for normality and homogeneity of variances using Levene's test. A Student's t-test was initially applied to compare means between duplicates within each size class at both sampling dates. As no significant differences were detected between duplicates (P > 0.05), the data were subsequently pooled. A second Student's t-test was then performed to compare growth performance between the two sampling dates (June 2023 and May 2024). Differences were considered statistically significant at P < 0.05. (Tab. 1).

3 Results

3.1 Environmental parameters

During the study period, seawater temperature recorded from June 2023 to May 2024 varied between 15.32 °C in March 2024 and 27.99 °C in August 2024 (Fig. 4A). Chlorophyll-a concentration ranged from 0.1 μg L−1 in May 2023 to 0.3 μg L−1 in March 2024 (Fig. 4A). Meanwhile, dissolved oxygen concentration remained relatively stable throughout the rearing period, with an average value of 7.94 mg L−1 recorded in February 2024 (Fig. 4B). Salinity varied slightly, reaching a maximum of 38.01 in September 2023 and a minimum of 36.83 in May 2023 (Fig. 4C).

Thumbnail: Fig. 4 Refer to the following caption and surrounding text. Fig. 4

Monthly variability of environmental parameters: (A) Temperature and Chlorophyll-a; (B) Dissolved oxygen; (C) Salinity in open sea (TTF farm; Monastir Bay, Tunisia) recorded during the study period from June 2023 to May 2024 extracted from Copernicus Marine Service (CMS) (Copernicus, 2025).
Thumbnail: Fig. 4 Refer to the following caption and surrounding text. Fig. 4

(Continued).

3.2 Growth, survival and condition index

Student’s t-test analysis performed on the duplicate for both the pre-fattening and fattening phases over the 316-day period showed no significant differences between duplicates (Tab. 1).

During the pre-fattening phase (June 2023 to May 2024), the mean shell length of clam seed increased, from 13.28 ± 1.52 mm to 15.28 ± 1.85 mm and from 10.79 ± 2.20 mm to 14.01 ± 1.25 mm for stage 1 and 2, respectively (Fig. 5A). The mean weights increased from 0.58 ± 0.24 g to 1.03 ± 0.27 g and from 0.35 ± 0.12 g to 0.77 ± 0.20 g for stage 1 and 2, respectively (Fig. 5B).

During the fattening phase (June 2023 to May 2024), the increase in mean shell length of clam seed was slower compared with the pre- fattening phase, rising from 15.90 ± 1.53 to 16.82 ± 1.42 mm and from 20.37 ± 1.55 to 21.80 ± 2.72 mm for stage 6 and 7, respectively (Fig. 6A). The mean weights increased from 0.90 ± 0.38 g to 1.35 ± 0.32 g and from 1.92 ± 0.55 g to 2.38 ± 0.74 g for stage 6 and 7, respectively (Fig. 6B).

Our results revealed a mean length growth rate was higher in the pre-fattening compared to the fattening of 0.2 ± 0.08 mm·month⁻¹ vs 0.1 ± 0.03 mm·month⁻¹ with corresponding mean length gain of 2.6 ± 0.86 mm vs 1.18 ± 0.36 mm. Mean weight gain averaged 0.42 ± 0.03 g in the pre fattening and 0.35 ± 0.09 g in the fattening, with monthly weight growth rates of 0.040 ± 0.003 g·month⁻¹ and 0.033 ± 0.009 g·month⁻¹ respectively (Tab. 2).

Clam seed reared in suspended lantern nets in the open sea showed high survival rates (SR) in both phases, reaching 64.35% and 84.58% during the pre-fattening and fattening phases, respectively (Tab. 2).

The highest mortality was recorded in November at stage L1–2 of the pre-fattening phase, 49.59%. In contrast, mortality at other stages remained relatively low, not exceeding 36.13% during pre-fattening phase and 4.41% during the fattening phase (Tab. 2).

The condition index of clam seed showed no significant difference between November and May after 316 days of rearing in the open sea within the IMTA system, remaining relatively stable at 5.41 ± 0.75, with values of 5.57 ± 0.80 in November 2023 and 5.29 ± 0.79 in May 2024 during the fattening phase (Fig. 7).

Thumbnail: Fig. 5 Refer to the following caption and surrounding text. Fig. 5

Box plots of distribution of shell length in mm (A) and weight in g (B) based on pooled data from duplicate per size class during the pre-fattening phase reared in suspended lanterns in open sea from June 2023 to May 2024. Student's t-test: P < 0.001. Mid-line: median; box: 25th and 75th percentiles; whiskers: 1.5 × the interquartile range.
Thumbnail: Figure 6 Refer to the following caption and surrounding text. Figure 6

Box plots of distribution of shell length in mm (A) and weight in g (B) based on pooled data from duplicate per size class during the fattening phase reared in suspended lanterns in open sea from June 2023 to May 2024 Student's t-test: P < 0.001. Mid-line: median; box: 25th and 75th percentiles; whiskers: 1.5 × the interquartile range.
Table 2

Main data concerning clam seed Length and Weight growth rate, Length gain, Weight gain and Survival Rate (SR) after 316 days of rearing in the open sea in IMTA system.

Thumbnail: Figure 7 Refer to the following caption and surrounding text. Figure 7

Variation of the Condition Index CI of European clam Ruditapes decussatus spat (n = 15) during the fattening phase after 316 days of rearing in suspended lanterns in the open sea in IMTA system.

4 Discussion

The present study is the first to address the rearing of the European clam R. decussatus in suspended lantern nets in the open sea within an IMTA system. Several studies conducted in open-sea environments have investigated clam growth. The results of this comparison are presented in Table 3.

The mean weight and length growth rates of R. decussatus recorded in the present study were 0.040 ± 0.003 g·month⁻¹ and 0.2 ± 0.08 mm·month⁻¹, respectively, over 316 days of rearing. These values are lower than those reported by Devic (2010) and Giovanardi and Boscolo (2003) using the same culture technique in open-sea conditions over 15 weeks and 5 months, with growth rates of 0.26 g·month⁻¹ and −0.39 mm·month⁻¹, respectively. However, they remain markedly lower than those observed in lagoon systems where higher growth performance has been reported (e.g. 0.5 g·month⁻¹ in the Thau lagoon).

The reduced growth observed in the present study is likely related to limited food availability, as indicated by low chlorophyll-a concentrations recorded during the study period (June 2023–May 2024), ranging between 0.1 and 0.3 μg L⁻¹. Such oligotrophic conditions may have strongly constrained bivalve growth, particularly during the pre-fattening phase, highlighting the critical role of chlorophyll-a concentrations in the development of bivalves.

In the present study, the mean length gain of R. decussatus was 2.6 ± 0.86 mm after 316 days of rearing for pre fattening individuals, which is considerably lower than that reported in environments with higher levels of chlorophyll-a concentrations.

In fact, several studies have demonstrated enhanced growth of R. decussatus under higher chlorophyll-a concentrations.

Our results are comparable to those reported by Medlouh et al. (2023) for hatchery-reared spat in suspended bags in the Oualidia Lagoon, Morocco. In their study, spats showed a growth gain of 2.6 mm, with individuals reaching a commercial size of 36.47 ± 1.54 mm. Although similar over a comparable rearing period 14 months, their study was conducted under higher chlorophyll-a concentrations of 0.63–2.43 μg L⁻¹.

Similarly, Bordignon et al. (2021) reported a higher growth of 8–10 mm within 10 weeks for clams reared in suspended lanterns in lagoon environments characterized by high chlorophyll-a concentrations ranged from 10 to 80 μg L⁻¹. However, Palazzi (2015), observed that hatchery-reared clam seed (∼1 mm initial size) reached 10–15 mm after only 45 days in suspended lanterns, likely due to nutrient-rich conditions with chlorophyll-a concentrations around 2.42 μg L⁻¹.

Comparable results have also been reported in other lagoon systems using alternative rearing techniques. Zanella et al. (2025) and Chessa et al. (2013) documented high growth performance of hatchery-reared clam seed in lagoon environments using a FLUPSY (Floating Upwelling System). Shell length increased from 1.8 mm to 16.9 mm within 53 days and from 10.88 ± 0.91 mm to 19.60 ± 1.11 mm after three months of rearing growth gain of 8.72 mm, under chlorophyll-a concentrations ranging approximately from 1 to 3 μg L⁻¹ and from 0.79 ± 0.55 to 5.63 ± 2.04 μg L⁻¹.

Taken together, these studies highlight the potential of lagoon systems over open-sea environments to provide suitable environmental conditions, particularly in terms of phytoplankton availability and high chlorophyll-a concentrations, which are essential for bivalve growth and development (Shafee and Sabatie, 1986; Jara-Jara et al., 1997; Ren and Schiel, 2008; Kaddioui et al., 2018; Sakurai et al., 2021).

In the present study, the condition index CI remained at 5.41 ± 0.75 from June 2023 to May 2024. This value is lower than previously reported CI values for R. decussatus reared in sheltered environments in Tunisia such as lagoons and foreshore sites. For example, CI values of 12.4 ± 1.4 have been reported for clams ranging from 30 to 46 mm in shell length during the fattening phase, collected from Oued Maltine (Gulf of Gabès) and Boughrara lagoon in southern Tunisia (Hamida et al., 2004; Medhioub et al., 2013). This difference may be attributed to variation in rearing techniques and environmental conditions.

In fact, R. decussatus, a burrowing bivalve species of the Veneridae family, naturally inhabits sandy-muddy substrates (Parisi et al., 2012; Anhichem et al., 2021; Medlouh et al., 2026). Several studies have shown that the use of substrate during rearing enhances growth performance and survival (Medhioub and Limayem, 1995). For instance, Dhraief et al. (2009), reported better growth of R. decussatus on the foreshore of the Gulf of Gabès (Zarrat foreshore), with a shell length gain of 6.85 mm after 11.2 months of rearing, which was substantially higher than that observed in the present study. Similarly, Serdar et al. (2007), reported higher growth rates for R. decussatus reared in the Sufa Lagoon (İzmir, Turkey) using alternative culture methods, including hard plastic nets (7.44 mm year⁻¹), net boxes (5.77 mm year⁻¹), polyamide nets (5.44 mm year⁻¹), and fenced ground systems (5.05 mm year⁻¹), all of which exceeded the growth performance recorded in the present study.

Furthermore, Sea Fish Report (1992) demonstrated that clams reared on the Scottish west coast using substrate-based methods exhibited higher growth and survival rates than those cultured in suspension, with 29% of clams reaching commercial size (>39 mm). Pais et al. (2006) also reported that rearing R. decussatus in coarse sand baskets in the Calich lagoon (northwest Sardinia) yielded high survival, significant shell growth, and favorable shell morphology.

Compared with our study, these findings suggest that substrate-based rearing systems can promote better growth performance than suspended culture and emphasize the critical role of rearing techniques in determining the growth performance of clam seed. Indeed, mollusk growth is strongly influenced by both environmental conditions and culture methods (Kaddioui et al., 2018; Medlouh et al., 2023).

In the present study, the growth gain during the pre-fattening phase was 2.6 ± 0.86 mm, approximately three times higher than that recorded during the fattening phase 1.18 ± 0.36 mm after 316 days of rearing (from June 2023 to May 2024). Previous studies have suggested that the decline in bivalve growth with increasing age is linked to reduced metabolic activity, lower filtration and feeding rates, and increased energy allocation to reproduction process (Mitchell et al., 2000; Pouvreau et al., 2000; Medhioub et al., 2023; Medlouh et al., 2026). Therefore, the low growth observed during the fattening phase in the present study may be related to metabolic constraints associated with aging and reproductive investment in this species.

Clam seed reared in suspended lanterns in the open sea exhibited high survival rates in both phases, reaching 64.35% and 84.58% during the pre-fattening and the fattening phases, respectively. These results emphasize the important role of temperature as a key environmental factor influencing bivalve physiology, including growth, reproduction, feeding, behavior, and respiration, and acting as a major driver of overall performance (Sobral and Widdows, 1997; Gosling, 2003; Fly and Hilbish, 2013; De Kantzow et al., 2016; Gharbi et al., 2016; Treviño et al., 2020).

During the summer period, water temperature in the Bay of Monastir can exceed 30 °C (Chaouch et al., 2024), potentially causing marine heatwaves that lead to mass mortality events in shellfish production (Deutsch et al., 2015; Thomas and Bacher, 2018; Buer et al., 2020). This observation is consistent with several studies reporting high mortality rates in both seed and adult molluscs, in some cases reaching up 100%. For example, the Mediterranean mussel Mytilus galloprovincialis is highly sensitive to thermal stress and shows reduced tolerance to temperatures above 28–31 °C (Matias et al., 2013; Gazeau et al., 2014; Gosling, 2015).

In the Bizerte lagoon, high mortality of spat mollusks was reported in August 2012, resulting in production losses of up 90%. Martinez et al. (2018), attributed this mortality primarily to evaluated summer temperatures, which typically range from 27 to 30 °C, and can peak at 40 °C. In addition to thermal stress, lagoon environments can pose a major risk to cultured shellfish due to potentially toxic algae, such as Pseudo-nitzschia spp. and Alexandrium spp, which may trigger dystrophic events and hypoxic conditions (Turki et al., 2014; Kristiansen and Butenschön, 2022).

The high survival rates of 64.35 and 84.58% observed in the present study can be also attributed to the rearing technique. Suspended culture is a widely used farming method for many bivalve species such as mussels, oysters, and scallops (Pais et al., 2006; Marshall and Dunham, 2013; Lebata-Ramos et al., 2021). Numerous studies have reported that the pre-fattening phase of clams is commonly conducted using suspended systems such as net cages, pearl nets, or lantern nets. This method provides several advantages, including accelerated growth, enhanced survival, improved control and cleaning, more efficient harvesting, and a reduced ecological footprint, particularly when integrated into multi-trophic aquaculture systems (Boscolo and Giovanardi, 2003; Bordignon et al., 2021; Oliva et al., 2021; Palazzi, 2015; Medlouh et al., 2023).

Overall, although growth performance remained limited, these results suggest that offshore suspended culture may provide a suitable strategy for maintaining clam seed survival under stressful summer conditions. This approach could therefore be considered as “storage” phase during periods of elevated temperature, unlike studies focused on growth.

In fact, the current experiment was proposed as an alternative approach to maintain clam seed survival during extreme summer heatwaves in the open sea. This study has been confirmed by several authors who demonstrate the potential of offshore rearing in providing strong water exchange and good oxygenation beneficial for shellfish culture. For instance, the blue mussel spat Mytilus edulis and oysters Crassostrea gigas and Ostrea edulis reared under open-sea condition reported high condition indices and favourable growth rates (Pogoda et al., 2013; Guillou et al., 2023). According to Boscolo and Giovanardi (2003), offshore suspended rearing may be a good strategy, as environmental conditions in the open sea are more favorable than those in lagoon systems. Besides, water currents play a key role in supplying dissolved oxygen and maintaining nutrient availability (Jaafar Kefi and Mleiki, 2016). Proper water ventilation and circulation strongly influence the vital processes of cultured species, particularly mollusks, by enhancing food supply, oxygen solubility, plankton distribution, and the removal of CO2 and other organic residues from the marine environment (Nair and Nayak, 2023). Furthermore, offshore suspended farming can improve the hygiene and the health status of farmed organisms by reducing pathogen pressure and disease prevalence (Steeves et al., 2018; Mizuta and Wikfors, 2019; Medhioub et al., 2023) which can be explained by the maintenance of the CI of 5.41 ± 0.75 (Boscolo and Giovanardi, 2003).

Overall, we can suggest that R. decussatus can be considered as a suitable candidate species for integration into pre-existing offshore IMTA systems, owing to its high filtration capacity. Several studies have stated bivalves mainly mussels and oysters as suitable candidates for IMTA due to their high filtration abilities (Pensa et al., 2022). The integration of clams within fish farming systems reduces ammonia levels in water and consequently improves water quality (Cunha et al., 2019; Domingues et al., 2020; Tacon et al., 2022; Kumara et al., 2023). For instance, Atlam (2024), reported a significant increase in the weight of European clams R. decussatus reared in seabass ponds, from 4.00 ± 0.01 g to 12.54 ± 0.03 g after 60 days, with a survival rate of 75.20 ± 1.60%. Similarly, Yao et al. (2025), demonstrated that the co-culture of razor clams with swimming crabs and kuruma shrimp improved water quality. Likewise, Essa et al. (2025), showed that the water quality was much better in tanks combining seabass and clams compared to seabass only.

Table 3

Comparative growth performance and survival rate of R. decussatus reared under different culture systems.

5 Conclusions

The present study demonstrates, for the first time, the feasibility of rearing hatchery-produced European clam R. decussatus in suspended lantern nets deployed on a pre-existing offshore longline structure originally designed for the cultivation of the Mediterranean mussel Mytilus galloprovincialis, within an IMTA system under open-sea conditions in Monastir Bay, Tunisia.

Under these conditions, clam seed exhibited relatively low growth rates but high survival throughout the 316-day experimental period, despite the relatively low chlorophyll-a concentrations characteristics of open sea environment. These findings suggest that this species can be temporarily maintained under offshore conditions, particularly during the summer period. In this context, offshore environments may represent a promising alternative for the temporary rearing of clam seed.

Moreover, owing to their high filtration capacity, clam seed may represent a suitable candidate species for integration into IMTA systems. However, further investigations are required to better assess and validate their functional role and ecological contribution within such systems.

Acknowledgments

This work was conducted within the framework of the European project Promoting and Developing Sustainable and Integrated Multi-Trophic Aquaculture (PATINER) (www.patiner.eu), coordinated by the Aquaculture Laboratory (LR 16 INSTM 03) of the National Institute of Marine Sciences and Technologies (INSTM). The authors would like to thank Offshore fish farm staff of TTF who supported us and facilitated the sampling of shellfish.

References

  • Anhichem M, Yahyaoui A, Adil O, Bessa A, Benbrahim S. 2021. Evaluation of the growth potential and contamination of the European clam (Ruditapes decussatus), raised using the suspension culture technique at the Oualidia lagoon in Morocco. AACL Bioflux 14(2): 786-803. [Google Scholar]
  • Asplund ME, Baden SP, Russ S, Ellis RP, Gong N, Hernroth BE. 2014. Ocean acidification and host–pathogen interactions: blue mussels, Mytilus edulis, encountering Vibrio tubiashii. Environ Microbiol 16: 1029–1039. [Google Scholar]
  • Atlam AI. 2024. Integrated multitrophic aquaculture of the seabass (Dicentrarachus labrax) with two types of clams and the whiteleg shrimp (Litopenaeus vannamei) for increased production and better sustainability in Egypt. Egypt J Aquatic Biolo Fish 28: 901–927. [Google Scholar]
  • Azirar R, Janah H, Aghzar A, Ouagajjou Y. 2024. Effect of stocking density on larval performance and post-larvae settlement of clam Ruditapes decussatus (Linnaeus, 1758) in bivalve hatchery production. E3S Web Conf 492: 02002. [Google Scholar]
  • Barton A, Hales B, Waldbusser GG, Langdon C, Feely RA. 2012. The Pacific oyster, Crassostrea gigas, shows negative correlation to naturally elevated carbon dioxide levels: implications for near‐term ocean acidification effects. Limnol& Oceanogr 57: 698–710. [Google Scholar]
  • Bordignon F, Trocino A, Rossetti E, Zomeño C, Pascual A, Birolo M, Llorens SM, Xiccato G. 2021. Effect of stocking density on growth and survival of juvenile Manila clams (Ruditapes philippinarum) farmed in suspended lanterns in a North Italian lagoon. Aquac Rep 20: 100719. [Google Scholar]
  • Boscolo R, Giovanardi O. 2003. Condition index and air survival time to compare three kinds of Manila clam Tapes philippinarum (Adams & Reeve) farming systems. Aquac Int 11: 243–254. [Google Scholar]
  • Boyd SL. Trophic Transfer of Metals from Seaweed to Shellfish in an Aquaculture System (Master’s Thesis), The Faculty of Western Washington University, 2023. [Google Scholar]
  • Buck BH, Nevejan N, Wille M, Chambers MD, Chopin T. Offshore and multi-use aquaculture with extractive species: seaweeds and bivalves, in: B.H. Buck, R. Langan (Eds.), Aquaculture Perspective of Multi-Use Sites in the Open Ocean, Springer International Publishing, Cham, 2017, pp. 23–69. [Google Scholar]
  • Buer A-L, Maar M, Nepf M, Ritzenhofen L, Dahlke S, Friedland R, Krost P, Peine F, Schernewski G. 2020. Potential and feasibility of Mytilus spp. farming along a salinity gradient. Front Mar Sci 7: 371. [Google Scholar]
  • Chaouch S, Harzallah A, Brahim M, Zarrad R, Sammari C. 2024. A three-dimensional hydrodynamic model for the Gulf of Hammamet-Bay of Monastir: model validation and application. J Coast Conserv 28: 11. [Google Scholar]
  • Chessa G, Serra S, Saba S, Manca S, Chessa F, Trentadue M, Fois N. 2013. The floating upwelling system (FLUPSY) for breeding of Venerupis decussata (Linnaeus, 1758) juveniles in a coastal lagoon in Sardinia (Italy). [Google Scholar]
  • Chopin T. Aquaculture, integrated multi-trophic (IMTA), in: P. Christou, R. Savin, B.A. Costa-Pierce, I. Misztal, C.B.A. Whitelaw (Eds.), Sustainable Food Production, Springer New York, New York, NY, 2013, pp. 184–205. [Google Scholar]
  • Clawson G, Kuempel CD, Frazier M, Blasco G, Cottrell RS, Froehlich HE, Metian M, Nash KL, Többen J, Verstaen J, Williams DR, Halpern BS. 2022. Mapping the spatial distribution of global mariculture production. Aquaculture 553: 738066. [CrossRef] [Google Scholar]
  • Copernicus. 2025. GLOBAL_ANALYSISFORECAST_BGC_001_028, https://doi.org/10.48670/moi-00015. [Google Scholar]
  • Copernicus. 2025. GLOBAL_ANALYSISFORECAST_PHY_001_024, https://doi.org/10.48670/moi-00016. [Google Scholar]
  • Cunha ME, Quental-Ferreira H, Parejo A, Gamito S, Ribeiro L, Moreira M, Monteiro I, Soares F, Pousão-Ferreira P. 2019. Understanding the individual role of fish, oyster, phytoplankton and macroalgae in the ecology of integrated production in earthen ponds. Aquaculture 512: 734297. [Google Scholar]
  • De Kantzow M, Hick P, Becker J, Whittington R. 2016. Effect of water temperature on mortality of Pacific oysters Crassostrea gigas associated with microvariant ostreid herpesvirus 1 (OsHV-1 μVar). Aquacult Environ Interact 8: 419–428. [Google Scholar]
  • Deutsch C, Ferrel A, Seibel B, Pörtner H-O, Huey RB. 2015. Climate change tightens a metabolic constraint on marine habitats. Science 348: 1132–1135. [Google Scholar]
  • Devic E. 2010. Diversification de la conchyliculture en Languedoc-Roussillon : évaluation du potentiel de croissance de la palourde européenne (Ruditapes decussatus) et du pétoncle noir (Chlamys varia) et essais de captage d’espèces d’intérêt maricole dans l’étang de Thau et sur les filières en mer ouverte au large de Thau. [Google Scholar]
  • DGPA. 2024. Marine Fishing and Aquaculture Statistics for the year 2024 (arabic version). Directorate-General for Fisheries and Aquaculture. [Google Scholar]
  • Domingues A, Rosa IC, Pinto Da Costa J, Rocha-Santos TAP, Gonçalves FJM, Pereira R, Pereira JL. 2020. Potential of the bivalve Corbicula fluminea for the remediation of olive oil wastewaters. J Clean Prod 252: 119773. [Google Scholar]
  • Dhraief MN, Hitonoi N, Zouari M, Guergef H, Lymayem Y, M’rabet R, Missaoui H, Kraiem MM. 2009. Grossissement des juveniles de palourdes Ruditapes decussatus (L., 1758), sur l’estran de Zarat (golfe de Gabes, Tunisie), dans des conditions experimentales. INSTM Bull: Mar Freshw Sci 36: 93–106. [Google Scholar]
  • Essa MAE-R, Srour TMA, Zahran S, Ashry AM, Habiba MM. 2025. Effect of integrated multi-trophic polyculture systems of marine fish and bivalves on European seabass (Dicentrarchus labrax) growth performance, feed utilization, and whole-body-proximate composition. Anim Rep 1: 75–84. [Google Scholar]
  • Fly EK, Hilbish TJ. 2013. Physiological energetics and biogeographic range limits of three congeneric mussel species. Oecologia 172: 35–46. [Google Scholar]
  • Gazeau F, Alliouane S, Bock C, Bramanti L, LÃpez Correa M, Gentile M, Hirse T, PÃrtner H-O, Ziveri P. 2014. Impact of ocean acidification and warming on the Mediterranean mussel (Mytilus galloprovincialis). Front Mar Sci 1. [Google Scholar]
  • Gharbi A, Farcy E, Van Wormhoudt A, Denis F. 2016. Response of the carpet shell clam (Ruditapes decussatus) and the Manila clam (Ruditapes philippinarum) to salinity stress. Biologia 71: 551–562. [Google Scholar]
  • Gharbi A, Fatnassi M, Zarrouk H, Ennouri R, Mili S. 2023. Clam harvesting in Tunisia: sustainability risks and SDG opportunities. JAMB 12: 72–78. [Google Scholar]
  • Gosling E. (Ed.), Bivalve Molluscs: Biology, Ecology and Culture, 1st edn, Wiley, 2003. [Google Scholar]
  • Gosling E. Marine Bivalve Molluscs, 1st edn, Wiley, 2015. [Google Scholar]
  • Guillou E, Androuin T, Toupoint N, Tremblay R. 2023. Selective pressure on ontogenic stages of blue mussels (Mytilus edulis, L.). J Exp Mar Biol Ecol 568: 151940. [Google Scholar]
  • Hamida L, Medhioub MN, Cochard JC, Romdhane MS, Le Pennec M. 2004. Étude comparative du cycle de reproduction de la palourde Ruditapes decussatus en milieu naturel (sud Tunisie) et contrôlé (écloserie). [Google Scholar]
  • IPCC. 2023. Climate Change 2023: Synthesis Report. Contribution of Working Groups I, II and III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, H. Lee and J. Romero (eds.)]. IPCC, Geneva, Switzerland. First, Intergovernmental Panel on Climate Change (IPCC). [Google Scholar]
  • Jaafar Kefi F, Mleiki A. 2016. Seasonal variations of trace metal concentrations in the soft tissue of Lithophaga Lithophaga collected from the bizerte bay (Northern Tunisia, Mediterranean Sea). J Aquac Res Dev 7. [Google Scholar]
  • Jara-Jara R, Pazos AJ, Abad M, García-Martín LO, Sánchez José L. 1997. Growth of clam seed (Ruditapes decussatus) reared in the wastewater effluent from a fish farm in Galicia (N.W. Spain). Aquaculture 158: 247–262. [Google Scholar]
  • Kaddioui A, Kassila J, ElMdari M, Errhif A. 2018. Aquaculture in Marocco: growth of Crassostrea gigas in two lagoons on the Atlantic shore. IJAR 6: 243–254. [Google Scholar]
  • Komatsu T, Komatsu T, Sasa S, Sasa S, Montani S, Montani S, Nishimura O, Nishimura O, Sakamaki T, Sakamaki T, Yoshimura C, Yoshimura C, Fujii M, Fujii M, Yanagi T, Yanagi T. Satoumi approach for realizing sustainable coastal use in a Riastype Bay: A case of Shizugawa Bay in Sakurai coast hit by the huge tsunami on 11 March 2011, in: Proceedings of International Conference “Managinag Risks to Coastal Regions and Communities in a Changinag World” (EMECS’11 - SeaCoasts XXVI). Presented at the Managing risks to coastal regions and communities in a changing world, Saint-Petersburg, Academus Publishing, 2017, pp. 1–1. [Google Scholar]
  • Kristiansen T, Butenschön M. 2022. An ensemble of trend preserving statistically downscaled projections for key marine variables under three different future scenarios for the North Sea. [Google Scholar]
  • Kumara R, Syamala K, Anand PSS, Chadha NK, Sawant PB, Prasad MS, Doddamani PL, Muralidhar AP. 2023. Effect of bivalves on water quality, microbial load and growth performance of P. vannamei and M. cephalus in halophyte-based integrated multi-trophic aquaculture reared under pond conditions. IJAR. [Google Scholar]
  • Lebata‐Ramos MaJHL, Dionela CS, Novilla SRM, Sibonga RC, Solis EFD, Mediavilla JP. 2021. Producing young, single and meaty oyster Crassostrea iredalei (Faustino, 1932) in grow‐out culture using pouches suspended from rafts. Aquac Res 52: 5270–5282. [Google Scholar]
  • Marshall RD, Dunham A. 2013. Effects of culture media and stocking density on biofouling, shell shape, growth, and survival of the Pacific oyster (Crassostrea gigas) and the Manila clam (Venerupis philippinarum) in suspended culture. Aquaculture 406–407: 68–78. [Google Scholar]
  • Martinez M, Mangano MC, Maricchiolo G, Genovese L, Mazzola A, Sarà G. 2018. Measuring the effects of temperature rise on mediterranean shellfish aquaculture. Ecol Indic 88: 71–78. [Google Scholar]
  • Mascorda Cabre L, Hosegood P, Attrill MJ, Bridger D, Sheehan EV. 2021. Offshore longline mussel farms: a review of oceanographic and ecological interactions to inform future research needs, policy and management. Rev Aquac 13: 1864–1887. [Google Scholar]
  • Matias D, Joaquim S, Leitão A, Massapina C. 2009. Effect of geographic origin, temperature and timing of broodstock collection on conditioning, spawning success and larval viability of Ruditapes decussatus (Linné, 1758). Aquac Int 17: 257–271. [Google Scholar]
  • Matias D, Joaquim S, Matias AM, Moura P, De Sousa JT, Sobral P, Leitão A. 2013. The reproductive cycle of the European clam Ruditapes decussatus (L., 1758) in two Portuguese populations: implications for management and aquaculture programs. Aquaculture 406–407: 52–61. [Google Scholar]
  • McFarland K, Jean F, Thébault J, Volety AK. 2016. Potential impacts of blooms of the toxic dinoflagellate Karenia brevis on the growth, survival and juvenile recruitment of the non-native green mussel Perna viridis in southeastern United States. Toxicon 109: 94–102. [Google Scholar]
  • Medhioub A, Mechri B, Bchir S, Limeyem Y, Slimani W, Aouni M, Medhioub MN. 2017. Impacts of rearing techniques on growth, survival and bacterial microbiota of carpet shell clam (Ruditapes decussatus) larvae. Aquac Int 25: 603–617. [Google Scholar]
  • Medhioub MN, Limayem Y. 1995. Effet d’un substrat sur la survie et la croissance de la palourde Ruditapes decussatus en phase de pré-grossissement 2. INSTM Bull: Mar Freshw Sci 22: 44–53. [Google Scholar]
  • Medhioub W, Amzil Z, Soudant Ph, Hamza A, Kraiem MN, Lassus P, Medhioub MN. 2013. Etude de l’impact de l’alimentation sur la detoxification de la palourde Ruditapes decussatus contaminee in-situ par les gymnodimines (lagune de Boughrara, sud de la Tunisie). INSTM Bull: Mar Freshw Sci 40: 73–85. [Google Scholar]
  • Medhioub W, Challouf R, Laabir M, Limayem Y, Bchir S, Slimeni W, El Amri D, Hamza A, Mahfoudhi M, Leblad BR, Medhioub MN, Abadie E, Rolland J-L, Azaza MS. 2023. Potential to produce brown mussel integrated to a net-cage fish farm in a Mediterranean bay. Aquac Rep 31: 101674. [Google Scholar]
  • Medlouh M, Doukilo I, Errhif A, Id Halla M, Belhsen OK. 2026. Reproductive biology and biochemical composition of the reared european clam Ruditapes decussatus (Mollusca: Bivalvia) in Oualidia Lagoon, Morocco. Oceans 7: 13. [Google Scholar]
  • Medlouh M, Doukilo I, Errhif A, Idhalla M. 2023. Development of a new rearing technique for the clam Ruditapes decussatus (Linnaeus, 1758) and evaluation of its zootechnical performance in the Oualidia Lagoon, Morocco 16. [Google Scholar]
  • Mille D, Blachier P. 2009. Mutation conchylicoles. E? tat des lieux et perspectives de development des productions en eau profonde a l’automne 2008 (Changing shellfish aquaculture practice: status and development perspectives of deep water production, Fall 2008). Aglia Rep Febr. [Google Scholar]
  • Mitchell IM, Crawford CM, Rushton MJ. 2000. Flat oyster (Ostrea angasi) growth and survival rates at Georges Bay, Tasmania (Australia). Aquaculture 191: 309–321. [Google Scholar]
  • Mizuta DD, Wikfors GH. 2019. Seeking the perfect oyster shell: a brief review of current knowledge. Rev Aquac 11: 586–602. [Google Scholar]
  • Nair NV, Nayak PK. 2023. Exploring water quality as a determinant of small-scale fisheries vulnerability. Sustainability 15: 13238. [Google Scholar]
  • Oliva D, Célis ADP, Abarca A, Pizarro M, Durán LR. 2021. Pre-engorda de semillas de cultivo de la almeja taquilla, Mulinia edulis, en un sistema suspendido en el mar. RBMO 55: 183–190. [Google Scholar]
  • Pais A, Chessa L, Serra S, Ruiu A. 2006. An alternative suspended culture method for the Mediterranean carpet clam, Tapes decussatus, in the Calich lagoon (North Western Sardinia). [Google Scholar]
  • Papageorgiou N, Dimitriou PD, Chatzivasileiou D, Tsapakis M, Karakassis I. 2023. Can IMTA provide added ecosystem value services in the fish farms of Greece? Front Mar Sci 9: 1083099. [Google Scholar]
  • Parisi G, Centoducati G, Gasco L, Gatta PP, Moretti VM, Piccolo G, Roncarati A, Terova G, Pais A. 2012. Molluscs and echinoderms aquaculture: biological aspects, current status, technical progress and future perspectives for the most promising species in Italy. Ital J Anim Sci 11: e72. [Google Scholar]
  • Pensa D, Fianchini A, Grosso L, Ventura D, Scardi M, Rakaj A. Tracking Population Status and Structure of Mediterranean Pen Shell Pinna Nobilis After a Mass Mortality Outbreak, 2022. [Google Scholar]
  • Palazzi R. 2015. Ottimizzazione del preingrasso lagunare della Vongola Verace. Relazione finale, Veneto Agricoltura, Sezione Innovazione e Sviluppo, Centro Ittico Sperimentale Bonello, 25 pp. [Google Scholar]
  • Pogoda B, Buck BH, Saborowski R, Hagen W. 2013. Biochemical and elemental composition of the offshore-cultivated oysters Ostrea edulis and Crassostrea gigas. Aquaculture 400–401: 53–60. [Google Scholar]
  • Pouvreau S, Tiapari J, Gangnery A, Lagarde F, Garnier M, Teissier H, Haumani G, Buestel D, Bodoy A. 2000. Growth of the black-lip pearl oyster, Pinctada margaritifera, in suspended culture under hydrobiological conditions of Takapoto lagoon (French Polynesia). Aquaculture 184: 133–154. [CrossRef] [Google Scholar]
  • Ren JS, Schiel DR. 2008. A dynamic energy budget model: parameterization and application to the Pacific oyster Crassostrea gigas in New Zealand waters. J Exp Mar Biol Ecol 361: 42–48. [Google Scholar]
  • Riquet F, Sanchez F, Antajan E, Bru N, Caill‐Milly N. 2026. The international manila and european clams conference: euro‐mediterranean overview and future directions to support sustainable clam fisheries. Aquat Living Resour 39: 4. [Google Scholar]
  • Rodrigues LC, Bergh JCJMVD, Massa F, Theodorou JA, Ziveri P, Gazeau F. 2015. Sensitivity of mediterranean bivalve mollusc aquaculture to climate change, ocean acidification, and other environmental pressures: findings from a producer survey. J Shellfish Res 34: 1161–1176. [Google Scholar]
  • Sakurai I, Mori T, Hisatomi Y. 2021. Experimental study on the possibility of a suspended culture of the Japanese littleneck clam Ruditapes philippinarum in Suttsu fishing port, Hokkaido. Fish Sci 87: 239–251. [Google Scholar]
  • Sanz-Lazaro C, Sanchez-Jerez P. 2020. Regional Integrated Multi-Trophic Aquaculture (RIMTA): Spatially separated, ecologically linked. J Environ Manag 271: 110921. [Google Scholar]
  • Sea Fish Report. 1992. Assessment of the potential for manila clam (Tapes philippinarum) cultivation on the Scottish West Coast (No. 400). Sea Fish Industry Authority Marine Farming Unit, Ardtoe. [Google Scholar]
  • Serdar S, Lök A, Köse A, Yildiz H, Acarli S, Goulletquer P. 2007. Growth and survival rates of carpet shell clam (Tapes decussatus Linnaeus, 1758) using various culture methods in Sufa (Homa) Lagoon, Izmir, Turkey. Aquac Eng 37: 89–99. [Google Scholar]
  • Shafee MS, Sabatie MR. 1986. Croissance et mortalite des huitres dans la lagune de Oualidia (Maroc). Aquaculture 53: 201–214. [Google Scholar]
  • Smaal AC. Goods and Services of Marine Bivalves, 1st edn, Springer International Publishing AG, Cham, 2019. [Google Scholar]
  • Sobral P, Widdows J. 1997. Effects of copper exposure on the scope for growth of the clam Ruditapes decussatus from southern Portugal. Mar Pollut Bull 34: 992–1000. [Google Scholar]
  • Steeves LE, Filgueira R, Guyondet T, Chassé J, Comeau L. 2018. Past, present, and future: performance of two bivalve species under changing environmental conditions. Front Mar Sci 5: 184. [Google Scholar]
  • Tacon AGJ, Metian M, McNevin AA. 2022. Future feeds: suggested guidelines for sustainable development. Rev Fish Sci& Aquac 30: 271–279. [Google Scholar]
  • Tan K, Zheng H. 2020. Ocean acidification and adaptive bivalve farming. Sci Total Environ 701: 134794. [Google Scholar]
  • Thomas Y, Bacher C. 2018. Assessing the sensitivity of bivalve populations to global warming using an individual‐based modelling approach. Glob Change Biol 24: 4581–4597. [Google Scholar]
  • Treviño L, Lodeiros C, Vélez‐Falcones J, Chávez‐Alcivar C, Isea‐León F, Bermúdez‐Medranda AE, Vélez‐Chica JC, Cruz‐Quintana Y, Leal D, Santana‐Piñeros AM, Rodríguez‐Pesantes D. 2020. Suspended culture evaluation of Pacific oyster Crassostrea gigas in a tropical estuary. Aquac Res 51: 2052–2061. [Google Scholar]
  • Troell M, Joyce A, Chopin T, Neori A, Buschmann AH, Fang J-G. 2009. Ecological engineering in aquaculture — potential for integrated multi-trophic aquaculture (IMTA) in marine offshore systems. Aquaculture 297: 1–9. [CrossRef] [Google Scholar]
  • Turki S, Dhib A, Fertouna-Bellakhal M, Frossard V, Balti N, Kharrat R, Aleya L. 2014. Harmful algal blooms (HABs) associated with phycotoxins in shellfish: What can be learned from five years of monitoring in Bizerte Lagoon (Southern Mediterranean Sea)? Ecol Eng 67: 39–47. [Google Scholar]
  • Wang J, Yang X, Wang Z, Ge D, Kang J. 2022. Monitoring marine aquaculture and implications for marine spatial planning—an example from Shandong Province, China. Remote Sensing 14: 732. [Google Scholar]
  • Williams GJ, Price NN, Ushijima B, Aeby GS, Callahan S, Davy SK, Gove JM, Johnson MD, Knapp IS, Shore-Maggio A, Smith JE, Videau P, Work TM. 2014. Ocean warming and acidification have complex interactive effects on the dynamics of a marine fungal disease. Proc R Soc B. 281: 20133069. [Google Scholar]
  • Yang B, Pu F, Li L, You W, Ke C, Feng D. 2017. Functional analysis of a tyrosinase gene involved in early larval shell biogenesis in Crassostrea angulata and its response to ocean acidification. Comp Biochem Physiol B: Biochem Mol Biol 206: 8–15. [Google Scholar]
  • Yao S, Liu H, Zhang D, Chen Y, Li S, He J, Xu W. 2025. The potential influence of clams on water quality improvement in mariculture ponds: a comprehensive assessment utilizing single-factor and water quality index (WQI) methods. Aquacult Int 33: 143. [Google Scholar]
  • Zanella L, Pastres R, Freguglia M, Stoppa S, Palazzi R. 2025. Effects of water flow rate and stocking density on the early pre-fattening of Manila clams (Ruditapes philippinarum) farmed in a North Adriatic “Valle da Pesca” (Italy). Aquac Int 33: 161. [Google Scholar]

Cite this article as: Harbaoui O, Medhioub W, Limayem Y, Zini R, Bchir S, Slimani W, Salah Azaza M. 2026. Growth and survival performance of European clam Ruditapes decussatus seed in suspended lantern nets in open sea, Bay of Monastir, Tunisia. Aquat. Living Resour. 39: 24. https://doi.org/10.1051/alr/2026020

All Tables

Table 1

Shell length (mean ± SD, mm) of duplicate per size class during the pre-fattening and fattening phases and number of individuals from June 2023 to May 2024. Inter-replicate Student's t-test P-values, pooled means and between-date comparisons.

In the text
Table 2

Main data concerning clam seed Length and Weight growth rate, Length gain, Weight gain and Survival Rate (SR) after 316 days of rearing in the open sea in IMTA system.

In the text
Table 3

Comparative growth performance and survival rate of R. decussatus reared under different culture systems.

In the text

All Figures

Thumbnail: Fig. 1 Refer to the following caption and surrounding text. Fig. 1

A: The geographic location of the study area in Tunisia; B: The experimental site located in Monastir Bay TTF farm (35°47’N 35°37’N, 10°45’E 11°50’E), C: Finfish cage of sea bass Dicentrarchus labrax and sea bream Sparus aurata with IMTA longline. Scales bars: A: 150km; B: 6,5km; C: 0, 2km.Source Esri, Maxar, Earthstar Geographics and GIS User Community.
In the text
Thumbnail: Fig. 2 Refer to the following caption and surrounding text. Fig. 2

(A) Illustration of two sizes of clams: pre-fattening and fattening phases; (B) placement of clams in 2 mm mesh traps; (C) the distribution of clams spat inside suspended lantern consisted of 8 stages; (D) the distribution of the pre-fattening group (stage 1 and 2) (shell length: <13.28 ±1.52 mm) and for the fattening group (stage 6 and 7) (shell length: >15.90 ± 1.53 mm) (E) the placement of lanterns at the IMTA longline.
In the text
Thumbnail: Fig. 3 Refer to the following caption and surrounding text. Fig. 3

Experimental IMTA systems. (1) mussel nylon bags, (2) oyster ropes, (3) clams suspended lanterns, (4) oyster suspended lanterns, (5) sea cucumber experimental suspended double-net trays, (6) ballast concrete, (7) macroalgae suspended lanterns, (8) second buoys, (9) principal buoys. L1: Lanterne1; L2: Lanterne 2.
In the text
Thumbnail: Fig. 4 Refer to the following caption and surrounding text. Fig. 4

Monthly variability of environmental parameters: (A) Temperature and Chlorophyll-a; (B) Dissolved oxygen; (C) Salinity in open sea (TTF farm; Monastir Bay, Tunisia) recorded during the study period from June 2023 to May 2024 extracted from Copernicus Marine Service (CMS) (Copernicus, 2025).
In the text
Thumbnail: Fig. 4 Refer to the following caption and surrounding text. Fig. 4

(Continued).
In the text
Thumbnail: Fig. 5 Refer to the following caption and surrounding text. Fig. 5

Box plots of distribution of shell length in mm (A) and weight in g (B) based on pooled data from duplicate per size class during the pre-fattening phase reared in suspended lanterns in open sea from June 2023 to May 2024. Student's t-test: P < 0.001. Mid-line: median; box: 25th and 75th percentiles; whiskers: 1.5 × the interquartile range.
In the text
Thumbnail: Figure 6 Refer to the following caption and surrounding text. Figure 6

Box plots of distribution of shell length in mm (A) and weight in g (B) based on pooled data from duplicate per size class during the fattening phase reared in suspended lanterns in open sea from June 2023 to May 2024 Student's t-test: P < 0.001. Mid-line: median; box: 25th and 75th percentiles; whiskers: 1.5 × the interquartile range.
In the text
Thumbnail: Figure 7 Refer to the following caption and surrounding text. Figure 7

Variation of the Condition Index CI of European clam Ruditapes decussatus spat (n = 15) during the fattening phase after 316 days of rearing in suspended lanterns in the open sea in IMTA system.
In the text

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.