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Occurrence of the lessepsian species Portunus segnis (Crustacea: Decapoda) in the Gulf of Gabes (Tunisia): First record and new information on its biology and ecology

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The alien blue swimming crab, Portunus segnis (Forskål, 1775), an Indo-Pacific species has been recorded in the Southern Mediterranean Sea since decades, even if its occurrence along the Tunisian coasts was not recorded yet. This paper reports the first record of P. segnis in the Gulf of Gabes, south-eastern Tunisia, with few observations on its biology and ecology. Twenty-four females of P. segnis were accidentally caught by local fishermen in October 2014 in shallow sandy areas covered mostly by seagrass and algal beds. Among these 24 individuals, 14 specimens (58.33%) were ovigerous. The mean carapace length (CL) and width (CW) of ovigerous females were 143.0 ± 5.8 mm and 67.8 ± 3.6 mm respectively, whereas in non ovigerous females these were 127.3 ± 6.8 mm and 58.9 ± 4.2 mm, respectively. The relationships between the size (CW and CL) and weight (TW) for ovigerous and non ovigerous females were also examined with non-linear equations. In addition, the mean number of eggs (fecundity) of 12 ovigerous females (whose mean CW = 143.3 ± 6.2 mm) was 777642 ± 80684. The correlations between fecundity and both CW and TW were found to be statistically significant.
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... Despite its economic and regional importance within fisheries in its native area (Abdel Razek et al. 2006;Anam and Mostarda 2012;Safaie et al. 2013a;Giraldes et al. 2016), and even in some localities within the Mediterranean Sea (Crocetta 2006;Ozcan 2012), there is limited biological or ecological information on this portunid species. Portunus segnis in Tunisian waters was first recorded in October 2014 (Rifi et al. 2014;Rabaoui et al. 2015); in August 2015 the species became very abundant in the region, with a 'bloom' 1 The Portunus pelagicus species complex was revised by Lai et al. (2010), prior to which P. segnis was considered by some authors to be synonymous with P. pelagicus. ...
... High abundance of this decapod in the receiving ecosystem could potentially alter trophic structure, modify natural benthic communities, reduce native biodiversity, threaten native species, and compete for and monopolise resources (CABI 2021). Portunus segnis was reported in Tunisia for the first time in 2014 (Rifi et al. 2014;Rabaoui et al. 2015). Rabaoui et al. (2015) noted its presence in the coastal zone at Ghannouch, where only 24 females were collected. ...
... Portunus segnis was reported in Tunisia for the first time in 2014 (Rifi et al. 2014;Rabaoui et al. 2015). Rabaoui et al. (2015) noted its presence in the coastal zone at Ghannouch, where only 24 females were collected. By the end of August in 2015, P. segnis had become very abundant, with 'blooms' occurring in coastal areas of the Gulf of Gabes (Crocetta et al. 2015), particularly in the central area between Zarrat and Ghannouch. ...
Article
The blue swimming crab Portunus segnis (Forskål, 1775) (family Portunidae) is one of the earliest Lessepsian invaders of the Mediterranean Sea and has been recorded for several decades in various Mediterranean areas. However, its presence on the southeastern Tunisian coast is very recent. This study describes the reproductive biology of the species in the Gulf of Gabes, including sex ratio, ovarian maturation, size at sexual maturity, spawning season and fecundity. Samples for biological investigation were collected from the commercial catches of trawlers and artisanal fishing units, from January to December in 2018. A total of 2 762 specimens, ranging from 19 to 158 mm carapace width (CW) and 0.638 to 356.109 g body weight (BW), were analysed. Females outnumbered males by 1.3 to 1 (1 581 vs 1 181 individuals). Sexual maturity was classified into five stages for females and three stages for males, based on visual observation of the colour and shape of the gonads. Spawning occurred three times during the year, with the first peak in May, the second in July, and the third—the most intensive peak—in October–November. Size at sexual maturity was 93.1 mm CW for males, and 93.6 mm CW for females. Females carried 142 242–2 640 080 eggs on their abdomen, with a positive linear relationship between fecundity and CW. The data presented in this study should be useful not only to detect variations in the reproductive cycle of P. segnis between regions but also to ensure sustainable management of the new fishery for the species in Tunisian waters.
... This significant decline was mainly attributed to industrial pollution from phosphate fertilizer industries dumping yearly ⁓10.95 million t of untreated wet phosphogypsum (⁓30 × 10 3 T/d of wet phosphogypsum; El Zrelli et al., 2018aZrelli et al., , 2019b into the coastal environment of Gulf of Gabes. These discharges have caused an extensive environmental chemical and radio-chemical pollution (El Zrelli et al., 2018b, 2019c, 2021a, 2023Rabaoui et al., 2014Rabaoui et al., , 2015aRabaoui et al., , b, 2017 and contributed to reduce the capacities of Posidonia to sustain ecosystem services (El Kateb et al., 2018;El Zrelli, 2017). ...
... The Gulf of Gabes is in a critical ecological situation as far as its seagrass ecosystem is concerned. Nearly 90 % of Posidonia meadows have already been destroyed or heavily degraded and biodiversity is decreasing drastically EC, 2017), which is further aggravated by invasive species such as the blue swimming crab (Portunus segnis; Rabaoui et al., 2015a;Crocetta et al., 2015;Shaiek et al., 2021), white-spotted jellyfish (Phyllorhiza punctata; Stamouli et al., 2017), Atlantic blue crab (Callinectes sapidus; Shaiek et al., 2021), brown shrimp (Penaeus aztecus; El Zrelli et al., 2021b). Such a situation results from the fact that Posidonia is highly sensitive to pollution and plays the critical role of habitat-forming species (sensu Lin et al., 2022) for the Gabesian coastal ecosystem and more generally for the coastal Mediterranean environment (Personnic et al., 2014). ...
Article
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... However, in less contaminated sites, different species have been found associated with seagrass as well as crawlers, carnivorous, suspension feeders, and herbivorous (Piló et al., 2015;Hu et al., 2019). Rabaoui et al. (2015) has studied the relationship between macrobenthic invertebrates and heavy metal enrichment in the Gulf of Gabes, Tunisia, and recorded a low number of species, density, and diversity in metal-polluted sites. ...
Chapter
This chapter presents information on the influence of major physicochemical factors including depth, temperature, salinity, turbidity, sediment texture, dissolved oxygen, pH, nutrients, organic matter, redox potential index, and contaminates on the marine benthos. Benthic assemblages encompassing macro and meiobenthos in all the regions including intertidal (soft and rocky), estuarine, coastal and deep seas occurring in different substrata are tied to the interplay of the environmental parameters. Salinity, dissolved oxygen concentration, temperature, depth, latitudinal variations, level of nutrients, and turbidity directly and indirectly influence the distribution, abundance, and larval survival of benthos as well as food availability among benthic organisms. Sediment composition is also interconnected to the complex relationship of other parameters with benthos besides contaminants. The establishment of a database on the environmental parameters in the benthic environment and their role in the distribution of benthic organisms will help monitor the benthic environment and its health.
... Among Portunidae crabs, P. segnis is one of the most commercially important true crabs in coastal waters of Persian Gulf and other areas worldwide (Hosseini et al., 2014). This species can inhabit a wide range of coastal and continental shelf ecosystems, including muddy, sandy and seagrass environments, from intertidal zone to at least 50 m depth (Rabaoui et al., 2015). However, few studies have been done on advantages of natural products extracted from this crab as drug's raw material (Anjugam et al., 2016;Bejaoui et al., 2017;Hamdi et al., 2018Hamdi et al., , 2020. ...
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... This can be explained by the influence of human activities in Boughrara, which disrupts the marine ecosystem and therefore causes destruction of their benthic communities (Darmoul et al. 1980;Kharroubi et al. 2011;Bejaoui et al. 2020). It can also be explained by the monthly fluctuations of the physiological condition of V. decussata and the nutrient abundance of their habitats (Albentosa et al. 2007) in addition to the vulnerability of clams to large predators such as the invasive crabs Portunus segnis (Forskål, 1775) (Rabaoui et al. 2015;Bejaoui et al. 2017). ...
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This study was carried out on the natural populations of Venerupis decussata from two Tunisian lagoons (North and Boughrara). Dynamics and morphological structures, growth and age characteristics of these clams were determined. Additionally, condition (CI) and gonadic (GI) indices were monthly determined from both populations. These indices were used as a tool in the determination of the harvesting period of this species which seems to be linked to the spring season. Our data showed that the dominant length ranged from 28.96 to 37.18 mm, while weight ranged from 17.91 to 20.98 and width ranged from 4.56 to 5.59 for both populations collected, respectively, from North Lagoon and Boughrara Lagoon. The morphological relationships indicated hypoallometry and hyperallometry between weight (2.347 ≤ b ≤ 2.816) and length (0.644 ≤ b ≤ 0.912), respectively. The marginal examination implied that only one growth increment was formed per year mainly during the summer season. The age class ranged from one to sixth with the dominance of the five age groups in the population of Boughrara as compared to the North Lagoon population, which reached the sixth age group. According to our results, the von Bertalanffy growth parameters were assumed and estimated to K 0.3 and 0.4 year−1 and L∞ 41 and 37.09 mm for the North and Boughrara populations, respectively. Furthermore, the growth performance index (Φ), age precision examination (IAPE), coefficient of age variation (CV) and annual growth rate (Gx) were assessed revealing that North population has a better growth rate as compared to the Boughrara one.
... In Tunisia, its invasive range covers the entire country coasts. It was recorded for the rst time in the Gulf of Gabès in 2015, but it has been assumed that its invasion occurred in Tunisian waters for at least two years before (Rabaoui et al. 2015). Like many invasive species, P. segnis invasion affected negatively native species, such as Carcinus aestuarii (C. ...
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