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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 | Saidi B.,National Institute of Sea science and Technologies | Bradai M.N.,National Institute of Sea science and Technologies
Journal of the Marine Biological Association of the United Kingdom | Year: 2014

In Tunisia, elasmobranch landings have decreased substantially in recent years. Generally, species-specific information is largely unavailable for artisanal fisheries, but it is essential to increase knowledge and to ensure proper management of these species. This study analysed elasmobranch catches with longline fishery in the Gulf of Gabès. In total, 21 and 20 pelagic and bottom longline fishing trips were conducted, respectively, from July to September in 2007 and 2008. A total of eight elasmobranch species were caught: four batoids and four sharks. Pelagic longline captures were hooked externally while a high number of individuals captured with bottom longline were hooked internally. Discards due essentially to low commercial value and size represented 7.6% of total number of elasmobranch specimens caught. Longline landings in the Gulf of Gabès were principally composed of sandbar shark, Carcharhinus plumbeus, representing, respectively, 94.14% and 21.17% in number of pelagic and bottom longline captures. The importance of rhinobatids and Mustelus capture with bottom longline reflect their abundance in this area compared to other Mediterranean zones. Juveniles, including neonates with umbilical scars, dominated carcharhnids specimens, while smoothhound and guitarfish captures were dominated by mature individuals. Mitigation measures based on gear modifications, size limits and delineated nursery areas in the Gulf of Gabès should be developed to protect these vulnerable species. © 2013 Marine Biological Association of the United Kingdom.


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: 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.

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