For many species, there is broad-scale dispersal of juvenile stages and/or long-distance migration of individuals and hence the processes that drive these various wide-ranging movements have important life-history consequences. Sea turtles are one of these paradigmatic long-distance travellers, with hatchlings thought to be dispersed by ocean currents and adults often shuttling between distant breeding and foraging grounds. Here, we use multi-disciplinary oceanographic, atmospheric and genetic mixed stock analyses to show that juvenile turtles are encountered ‘downstream’ at sites predicted by currents. However, in some cases, unusual occurrences of juveniles are more readily explained by storm events and we show that juvenile turtles may be displaced thousands of kilometres from their expected dispersal based on prevailing ocean currents. As such, storms may be a route by which unexpected areas are encountered by juveniles which may in turn shape adult migrations. Increased stormy weather predicted under climate change scenarios suggests an increasing role of storms in dispersal of sea turtles and other marine groups with life-stages near the ocean surface.

Factors of mortality of marine turtles in the Bay of Biscay. Factors of mortality in marine turtles near the French coast of the Bay of Biscay have been recorded for four species: leatherback (Dermochelys coriacea), loggerhead (Car&a carettu), Ridley's turtle (Lepidochelys kempii) and green turtle (Chelonia mydas). Most accidental captures of D. coriacea by fishing gears lead to drowning, but the main threat for the species is the ingestion of floating waste. Plastic bags induce occlusion or lesions in the stomach and subsequent death. For C. car-etta, L. kempii and C. mydas, the pathology points out mainly two features: external or internal mycosis. 0 Elsevier, Paris Chelonian I marine turtle I pathology I pollution / Bay of Biscay RCsumC -L'examen de 230 tortues marines trouvees sur la cbte franqaise du golfe de Gascogne a permis de rechercher les facteurs de mortalite chez quatre especes : Tortue Luth (Dermochelys coriacea), Caouanne (Caretta caretta), Tortue de Kemp (Lepidochelys kempii) et Tortue verte (Chelonia mydas). La noyade consecutive aux captures accidentelles dans les engins de p&he est frequente chez D. coriacea et l'ingestion de dechets flottants presente, a long terme, une grave menace pour l'espece. Les morceaux de plastique provoquent des occlusions ou des lesions infectieuses de l'estomac, dont l'issue est fatale. Chez C. caretta, L. kempii et C. mydas, les lesions dominantes sont celles dues aux mycoses externes et internes.

Among the seven species of existing sea turtles, four can be seen in the Bay of Biscay and in the Manche. The leatherback turtle Dermochelys coriacea (Vandelli, 1761) and the loggerhead turtle Caretta caretta (Linnaeus, 1758) are the most seen species whereas the Kemp's ridley turtle Lepidochelys kempii (Garman, 1880) and the green turtle Chelonia mydas (Linnaeus, 1758) are seen more occasionally. The monitoring of the sightings done by the Aquarium La Rochelle and its Center of Studies and Cares for Sea Turtles since 1988 allowed us to identify the main characteristics of the sea turtles present on the studied area.KEY WORDS: French Atlantic Coast, Dermochelys coriacea, Caretta caretta, Lepidochelys kempii, Chelonia mydas. RESUMENEntre las siete especies de tortugas marinas que existen, cuatro pueden observarse en el Golfo de Vizcaya y en el Canal de la Mancha. La tortuga laúd Dermochelys coriacea (Vandelli, 1761) y la tortuga boba Caretta caretta (Linnaeus, 1758) son las más frecuentes, mientras que la tortuga lora Lepidochelys kempii (Garman, 1880) y la tortuga verde Chelonia mydas (Linnaeus, 1758) se ven ocasionalmente. El seguimiento de avistamientos llevado a cabo por el Aquarium de La Rochelle y su centro de estudios y cuidado de tortugas marinas desde 1988 nos ha permitido identificar las características de las tortugas presentes en el área de estudio.

Measuring fish target strength (TS) in the wild is challenging because: (i) TS varies versus physical (orientation relative to the incident sound wave, size, and depth) and physiological fish attributes (maturity and condition), (ii) the target species and its aforementioned attributes are difficult to assess in near real time, and (iii) in the case of packed fish schools, accepted echoes may originate from multiple unresolved targets. We propose a method for controlled TS measurements of densely packed small pelagic fish during daytime, based on the joint use of a Remotely Operated Towed Vehicle, “EROC”, with a pelagic trawl fitted with a codend opening system, “ENROL”. EROC, equipped with a 70-kHz split-beam echosounder (Simrad EK60) and a low-light black and white camera, can be moved inside the fishing trawl. Pelagic fish are funnelled into the open trawl and their TS is measured in the middle of the net, where small groups actively swim towards the trawl mouth. The swimming behaviour allows for near-dorsal TS to be measured, minimizing the large effect of incidence angle on TS variability. The EROC camera, located near the open codend, provides optical identification of the species. This method was used to measure the TS of European Anchovy, Engraulis encrasicolus in the Bay of Biscay during 2014. The mean, near dorsal TS was −43.3 dB, for a mean fork length of 12.5 cm. This value is compared to published values of clupeiforms mean TS obtained for a range of natural incidence angles and discussed in the light of TS modelling results obtained for E. encrasicolus.

This study aims at (1) experimentally estimating first sexual maturation of the European sardine S. pilchardus, (2) using the results to calibrate existing bioenergetic models. During the 183 days-experiment, fish growth and body condition were assessed by biometry, and gonads were weighed when present. Age, wet weight and total length at first maturity were estimated at 262 days, 10.79 ± 0.75 g, and 11.26 ± 0.21 cm, respectively. Including these traits in biphasic Von Bertalanffy models did not significantly improve simulations for either length or weight data, meaning that energy allocation was not impacted by these traits. The implementation of the results in the Dynamic Energy Budget (DEB) calibration procedure strengthened the parameter set of the existing model, but resulted in significant changes in the energy allocation. Our results are a first step that will allow the design of new experiments to further quantify maturation and reproduction rates in diverse environmental conditions, consolidating DEB model calibration.