23 research outputs found
Invasion récente de la crevette asiatique Palaemon macrodactylus : cas de la Gironde (France)
International audienceThe shrimp Palaemon macrodactylus Rathbun, 1902 is a native species of Asian waters. It was introduced into California (USA) in the 1950s and it had recently been recorded in Mar del Plata Harbor (Argentina) and in several European estuaries, such as the Guadalquivir (Spain), the Orwell (England) and the Gironde (France). In Europe, Palaemon macrodactylus was recorded belatedly after its introduction and hence very few data about its ecology and possible interactions with local shrimps are available. Since 1979, a large part of the Gironde estuary had been monthly sampled for fauna survey (mainly fish). The date of the first apparition of the oriental shrimp Palaemon macrodactylus and its expansion were inferred from the examination of the preserved samples from 1992 to 2006. The distribution of the invasive species indicated a spatial overlap with the distribution of the native species Palaemon longirostris Milne Edwards, 1837 and Crangon crangon Linnaeus, 1758, according to the seasons. We particularly focused on the possible interactions with Palaemon longirostris which supports an important traditional fisheries in the Gironde estuary (73 tonnes in the 2005). The first ecological data about P. macrodacylus in this area are presented, particularly its spatial distribution and its reproductive characters. These results revealed that the exotic species had an ecological advantage compared to the native one. P. macrodactylus is becoming an abundant element of the Palaemonid community of Gironde. The strength of the exotic population may be responsible for the decrease in abundance of the native shrimp populations
L'introduction de la crevette exotique Palaemon macrodactylus dans l'estuaire de la Gironde risque-t-elle d'impacter la population de crevettes blanches natives P. longirostris ? : Quelques éléments de réponse
National audience5 espèces de crevettes sont recensées dans l'estuaire de la Gironde. En été 2006 on identifie la crevette exotique Palaemon macrodactylus. Etude de cette nouvelle espèce et comparaison avec la crevette blanche
A finer look into the twilight zone : comparing acoustic records from an animal-borne miniature sonar and a multifrequency echosounder [résumé]
ICES. Working Group of Fisheries Acoustics, Science and Technology (WGFAST), Somone, SEN, 25-/04/2022 - 28/04/2022An animal-borne miniature active echo-sounder has been recently deployed on southern ele-phant seals (Mirounga leonina) from the Kerguelen and Argentinian colonies. This high frequency sonar (1.5 MHz) has shown a strong potential in detecting small mid-trophic level targets (zoo-plankton and micronekton). Relative abundance and distribution can be assessed, allowing to observe temporal (diel migration) and spatial patterns of plankton. However, the interpretation of the collected data remains uncertain. To address this lack of information, we conducted in situ experiments onboard the Marion Dufresne vessel in the Southern Ocean (10th February to 6th March 2022). The microsonar was fixed on the rosette sampler at 13 locations and attached 16 times to a trawling net (4 mm mesh). Records will be analyzed applying a recent method devel-oped on elephant seals data to detect targets in the beam and estimate organisms abundance. The result will be compared with biological samples and backscattering layers detected by a multifrequency EK80 echosounder (18, 38, 70, 120 and 200 kHz), offering an acoustic landscape of the seals foraging area. This study will benefit to ongoing research regarding biological fields visited by the elephant seals, bringing precision on microsonar target detection capacities
A finer look into the twilight zone : comparing acoustic records from an animal-borne miniature sonar and a multifrequency echosounder [résumé]
ICES. Working Group of Fisheries Acoustics, Science and Technology (WGFAST), Somone, SEN, 25-/04/2022 - 28/04/2022An animal-borne miniature active echo-sounder has been recently deployed on southern ele-phant seals (Mirounga leonina) from the Kerguelen and Argentinian colonies. This high frequency sonar (1.5 MHz) has shown a strong potential in detecting small mid-trophic level targets (zoo-plankton and micronekton). Relative abundance and distribution can be assessed, allowing to observe temporal (diel migration) and spatial patterns of plankton. However, the interpretation of the collected data remains uncertain. To address this lack of information, we conducted in situ experiments onboard the Marion Dufresne vessel in the Southern Ocean (10th February to 6th March 2022). The microsonar was fixed on the rosette sampler at 13 locations and attached 16 times to a trawling net (4 mm mesh). Records will be analyzed applying a recent method devel-oped on elephant seals data to detect targets in the beam and estimate organisms abundance. The result will be compared with biological samples and backscattering layers detected by a multifrequency EK80 echosounder (18, 38, 70, 120 and 200 kHz), offering an acoustic landscape of the seals foraging area. This study will benefit to ongoing research regarding biological fields visited by the elephant seals, bringing precision on microsonar target detection capacities