National Institute of Sea science and Technologies

Sfax, Tunisia

National Institute of Sea science and Technologies

Sfax, Tunisia
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Jribi I.,University of Sfax | Bradai M.N.,National Institute of Sea science and Technologies
Scientific World Journal | Year: 2014

Hatchling sex ratios in the loggerhead turtle Caretta caretta were estimated by placing electronic temperature recorders in seven nests at Kuriat islands (Tunisia) during the 2013 nesting season. Based on the mean temperatures during the middle third of the incubation period, and on incubation duration, the sex ratio of hatchlings at Kuriat islands was highly male-biased. Presently, the majority of hatchling sex ratio studies are focused on major nesting areas, whereby the sex ratios are universally believed to be heavily female-biased. Here we present findings from a minor nesting site in the Mediterranean, where the hatchling sex ratio was found to be male-biased, suggesting a potential difference between major and minor nesting sites. © 2014 Imed Jribi and Mohamed Nejmeddine Bradai.


Echwikhi K.,National Institute of Sea science and Technologies | Echwikhi K.,University of Sfax | Jribi I.,University of Sfax | Bradai M.N.,National Institute of Sea science and Technologies | Bouain A.,University of Sfax
Aquatic Conservation: Marine and Freshwater Ecosystems | Year: 2010

1. Sea turtles may migrate vast distances from their feeding areas to home rookeries where they nest. During these migrations sea turtles are subject to many threats, among which are interactions with pelagic longlines. 2. This gear is used frequently in the summer period in the Gulf of Gabes targeting mainly the sandbar shark (Carcharhinus plumbeus). Hooks are baited with mackerel (Scomber scombrus) or pieces of stingray (Dasyatis pastinaca). 3. Twenty-one fishing trips (48 sets with a total of 35950 hooks deployed) were conducted using onboard observers in the south of the Gulf of Gabes during the months of July, August and September in 2007 and 2008. Stingray and mackerel bait were used in 19 and 29 sets, respectively. 4. In total, 29 loggerhead sea turtles (Caretta caretta) were captured; the majority of them were juvenile and active. Turtles were caught at a statistically greater frequency on sets with hooks baited with mackerel than on sets with hooks baited with pieces of stingray. 5. The type of bait also affected the catch of the target species by increasing the efficiency when pieces of stingrays were used. 6. These results encourage further research into new baits to mitigate turtle catch by longline fisheries without affecting the catch of target species. © 2010 John Wiley & Sons, Ltd.


Echwikhi K.,National Institute of Sea science and Technologies | Echwikhi K.,University of Sfax | Jribi I.,University of Sfax | Bradai M.N.,National Institute of Sea science and Technologies | Bouain A.,University of Sfax
Herpetological Journal | Year: 2010

Some gillnets used in the south of Tunisia (Gulf of Gabes) target shark species (Mustelus sp., Carcharhinus plumbeus) and guitarfish (Rhinobatos cemiculus, Rhinobatos rhinobatos). These artisanal nets interact with sea turtles. Here we present an analysis of the bycatch of loggerhead sea turtles Caretta caretta in these gillnets in the Gulf of Gabes, an important Mediterranean wintering and foraging area for this threatened species. We quantified mean catch per unit effort (CPUE) in three ways to account for uncertainty and found high levels of interaction in each case. The number of turtle captures per km2 of gillnet per day, the number of turtle captures per km of net and the number of turtle captures per set were 0.527 (0.403-0.649), 0.339 (0.250-0.438) and 0.800 (0.654-0.904), respectively. Captured loggerheads were mainly juveniles (mean = 56.6cm CCLn-t) and direct mortality was estimated as 69.4% (n=25). These are the first estimates of sea turtle interactions with artisanal fisheries for northern Africa, and one of very few estimates of turtle mortality in set gillnets in the Mediterranean. Our results indicate a need for research into ways for fishermen to avoid turtle captures and to raise awareness of this problem throughout the Mediterranean Sea. The following specific actions are recommended: 1) management of gillnet fisheries in the Mediterranean Sea, 2) minimizing gear soak time, particularly in foraging and inter-nesting habitats and along the migration pathways of sea turtles, 3) technical modifications of the gear by reducing the number of floats, and 4) carrying out an awareness campaign with fishermen to reduce post-release mortality.


Echwikhi K.,National Institute of Sea science and Technologies | Echwikhi K.,University of Sfax | Saidi B.,National Institute of Sea science and Technologies | Bradai M.N.,National Institute of Sea science and Technologies | Bouain A.,University of Sfax
Journal of Applied Ichthyology | Year: 2013

Elasmobranchs are an important catch component in Tunisian artisanal fisheries. Generally, species-specific information is largely unavailable for artisanal fisheries; an increase in knowledge thereof is essential to ensure proper management of these species. The study analyzed the gillnet fishery elasmobranch catches in the Gulf of Gabès, whereby 45 fishing trips were conducted from April to June 2007 and 2008 for the capture of a total of six species: three Rajiformes and three Carchariniformes. Rhinobatos cemiculus was the most important species (52%; 4.588 ind km-2 net per day). Among shark species, Mustelus mustelus was the most important (66.8%; 2.21 ind km-2 net per day). Discards represented 6.87% of total catch in weight and 14.28% in number of specimens caught. Size composition of captures varied by species, but usually mature, mainly gravid females were abundant. Further investigations are needed to obtain more information on such fragile species for the development of protective measures. © 2012 Blackwell Verlag, Berlin.


Echwikhi K.,National Institute of Sea science and Technologies | Echwikhi K.,University of Sfax | Jribi I.,University of Sfax | Bradai M.N.,National Institute of Sea science and Technologies | Bouain A.,University of Sfax
Journal of the Marine Biological Association of the United Kingdom | Year: 2012

In the Gulf of Gabès (Tunisia), a fleet of bottom longliners operates in summer and in the beginning of autumn targeting groupers. This fleet interacts with loggerhead turtles. During twenty trips in which 48,020 hooks were deployed, a total of 16 loggerheads were captured, most of them were juveniles, and direct mortality was estimated to be 43.75%. During the fishing operation, the hauling of the gear started one to three hours after and sometimes occurred immediately after setting. Results obtained show that the soak time did not affect the capture of turtles and target species, whereas it influenced the mortality rate of turtles. Bottom longline should be studied more in depth throughout the Mediterranean Sea, as well as parameters related to the interaction with sea turtles. However, mitigation measures to reduce turtle by-catch are urgently needed. In this way, we propose: (i) reducing the fishing soak time; (ii) experimenting with gear modification such as the use of circle hooks; and (iii) conducting an awareness campaign aimed at fishermen to show them how to deal with turtle by-catch. Copyright © Marine Biological Association of the United Kingdom 2011.


Echwikhi K.,National Institute of Sea science and Technologies | Echwikhi K.,University of Sfax | Jribi I.,University of Sfax | Bradai M.N.,National Institute of Sea science and Technologies | Bouain A.,University of Sfax
Aquatic Conservation: Marine and Freshwater Ecosystems | Year: 2012

In the Mediterranean Sea, trawl nets and drifting longlines have been recognized as methods that capture thousands or tens of thousands of turtles. However, the possible impact of other fishing methods has not been adequately addressed, especially for artisanal and amateur fisheries that use coastal nets. Coastal net fisheries, including driftnets and set nets, used at a much shallower depth (<40m) in the Mediterranean, result in a large bycatch of loggerhead turtles in the neritic zone. The mortality rate with these fisheries seems to be higher than with other commercial fisheries. In the Mediterranean context, additional assessments on fishery characteristics and fishing gear parameters to: (i) develop a simple and unanimous definition of an artisanal fishery; and (ii) standardize units for reporting sea turtle bycatch with coastal nets, are needed to provide an understanding of the current relative degree of risk coastal net fisheries pose to turtle populations. Mitigation measures based on (a) gear-technology approaches, (b) fisheries closures, and (c) increased awareness and education of fishermen, must be considered as priorities and should be implemented without further delay. © 2012 John Wiley & Sons, Ltd.


PubMed | University of Sfax and National Institute of Sea science and Technologies
Type: | Journal: TheScientificWorldJournal | Year: 2014

Hatchling sex ratios in the loggerhead turtle Caretta caretta were estimated by placing electronic temperature recorders in seven nests at Kuriat islands (Tunisia) during the 2013 nesting season. Based on the mean temperatures during the middle third of the incubation period, and on incubation duration, the sex ratio of hatchlings at Kuriat islands was highly male-biased. Presently, the majority of hatchling sex ratio studies are focused on major nesting areas, whereby the sex ratios are universally believed to be heavily female-biased. Here we present findings from a minor nesting site in the Mediterranean, where the hatchling sex ratio was found to be male-biased, suggesting a potential difference between major and minor nesting sites.


Ben Nasr I.,University of El Manar | Borgi A.,University of El Manar | Sellem F.,National Institute of Sea science and Technologies
2013 International Conference on Control, Decision and Information Technologies, CoDIT 2013 | Year: 2013

In this paper, we focus on expert knowledge incorporation in supervised learning tasks particularly decision rules. We aim to improve their quality, reduce their number and increase their prediction's rate. The proposed method consists of initially applying Knowledge Discovery in Databases process (KDD) on a database relating to Echinoderms. It aims to improve then classification rules' performance using background knowledge. This method is evaluated on a real domain area concerning Echinoderms. Experimental results are relevant; they generally improve performance and reduce prediction rules number. © 2013 IEEE.


Selmi S.,National Institute of Sea science and Technologies | Sadok S.,National Institute of Sea science and Technologies
Journal of Muscle Foods | Year: 2010

The seasonal lipid variation and fatty acids compositions were assessed in white and red muscles, head, viscera, liver and gonads of little tuna Euthynnus alletteratus. Lipid contents showed a significant variation (P < 0.05) throughout the year, the maximum level was found in the liver during winter season (27.28 g/100 g). The lowest fat contents were found in gonads during the winter and spring seasons, with levels of 1.56 and 1.49 g/100 g, respectively. White and red muscle fat levels increased significantly from winter to summer; viscera lipids, however, showed a significant decrease during the same period. Generally, the increase of the polyunsaturated fatty acids percentage in most organs was usually accompanied with a decrease of saturated fatty acids. It was shown that lipid content was higher in the head and liver compared to other compartments, and the fatty acid composition in the different organs of little tuna was significantly influenced by spawning and season. All lipids extracted contained significant amounts of docosahexaenoic acid and eicosapentaeneoic acid, which have various physiological functions Practical Applications: Most of the available literature showed little information about biochemical composition of fillets and by-products of some fish species and are, therefore, not complete for industrial purposes as application in food or feed nutriment. The practical application of this study was performed by the determination of fatty acids levels of little tuna fillets (white and red muscles) and by-products (head, viscera, liver and gonads) to further explain the evolution of lipid and fatty acids throughout the year. Finally, this manuscript may provide some valuable information for other scientists working in the field of food technology. © 2010, Wiley Periodicals, Inc.


Haouas W.G.,Higher Institute of Biotechnology of Monastir | Haouas W.G.,National Institute of Sea science and Technologies | Zayene N.,Higher Institute of Biotechnology of Monastir | Zayene N.,National Institute of Sea science and Technologies | And 3 more authors.
International Journal of Food Science and Technology | Year: 2010

In this study, we compared the lipid and fatty acids content, between cultured and wild Seriola dumerili, in different edible portions. Results showed that cultured fish contained a higher level of lipids than wild fish. The fatty acids profiles revealed that, among all the split-fish side, palmitic (C16:0) and oleic (C18:1n-9) acid were the principal saturated and monounsaturated fatty acids, in cultured and wild S. dumerili. On the other hand, wild S. dumerili contained a higher level of saturated (38.12 ± 0.54% vs. 33.66 ± 0.15% in cultured fish), monounsaturated (33.13 ± 1.07% vs. 26.49 ± 0.17%), n-3 polyunsaturated fatty acids (PUFA) (23.90 ± 1.02% vs. 19.77 ± 0.51%) particularly docosahexaenoic acid (DHA) (18.83 ± 0.48% vs. 11.77 ± 0.42%). However, the cultured fish showed a higher level of n-6 PUFA due principally to the higher value of linoleic acid (C18:2n-6). In fact, changes in fatty acids content between anatomical areas marked differences in the muscle quality of wild and cultured S. dumerili. According to this study, both groups of wild and farmed S. dumerili have nutritional benefits for human health. Cultured fish were characterised by higher hypocholesterolaemic and hypercholesterolaemic fatty acids ratio for all samples studied and a lower n-3/n-6 ratio due to the abundance of n-3 PUFA particularly DHA in wild fish. © 2010 Institute of Food Science and Technology.

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