Members of the Epinephelinae subfamily of serranids (‘grouper’) are heavily exploited by bottom longline in the Gulf of Gabès located in the south of Tunisia. In addition to direct mortality, hook and release mortalities likely occur when fish are caught and released, due to injuries sustained from hooking as well as those associated with retrieval. During five experimental trips (29 fishing sets) conducted in August 2011 from the port of Djerba (south of the Gulf of Gabès), we evaluated the effect of hook styles (9/0 ‘J’ and 12/0 circle hook) on groupers and non-target species. A total of 340 specimens representing 10 species were captured. The higher catch rate was registered for Epinephelus aeneus. The majority of groupers captured were female mature. The circle hook increased the capture of the most common grouper E. aeneus and did not affect the catch of Epinephelus marginatus and Epinepheleus costae. The effect of the type of hook on hooking location was inconclusive. Managing of the grouper fishery using some management actions such as size limits, bag limits, and closed seasons may prevent more unnecessary losses of grouper species. From this preliminary study, a definite conclusion for or against the use of circle hook cannot be drawn. Further research on the role of gear modification and hook designs in reducing by-catch, hooking-related injury and mortality should be encouraged.

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.

Une analyse des correspondances multiples et une classification ascendante hiérarchique ont été utilisées pour étudier les variations de rendements par espèce entre 1972 et 1989 de navires de la pêche chalutière hauturière française. L'application de ces méthodes permet de mettre en évidence les relations parfois complexes qui lient les rendements des principales espèces débarquées au sein des rendements totaux et de dégager une partition des profils de rendements caractéristique de cette période. Les facteurs comme l'année et les secteurs de pêche sont ceux qui expliquent le mieux les variations observées; les variations saisonnières jouent un rôle secondaire. Les rendements augmentent et se diversifient entre 1972 et 1989. L'étude montre que ces évolutions peuvent être reliées pour une part à des changements dans les stratégies d'allocation d'effort de pêche et dans la composition des flottilles. Les chalutiers qui exploitaient traditionnellement le golfe de Gascogne au début des annéessoixante-dix ont reporté leur effort sur des secteurs situés plus au nord (nord de l'Irlande et ouest de l'Ecosse) et ont été remplacés par des chalutiers de taille et de puissance plus importantes. Dans les années quatre-vingt, une autre composante fait son apparition. Elle est constituée par des chalutiers de taille plus réduite qui exploitent des secteurs plus côtiers que les précédents.