MOVEMENTS OF THREE LOGGERHEAD SEA TuRTLES IN TuSCANy WATERS (original) (raw)
Related papers
Marine Biology, 2012
Knowledge about migratory routes and highly frequented areas is a priority for sea turtle conservation, but the movement patterns of juveniles frequenting the Adriatic have not been investigated yet, although juveniles represent the bulk of populations. We tracked by satellite six juvenile and one adult female loggerhead from the north Adriatic. The results indicated that loggerhead juveniles (1) can either show a residential behaviour remaining in the Adriatic throughout the year or perform seasonal migrations to other areas, (2) can remain even in the coldest, northernmost area during winter, (3) can frequent relatively small foraging areas, (4) mostly frequent the eastern part of the Adriatic, and (5) follow preferred migratory routes along the western and eastern Adriatic coasts. The movements of the adult turtle also revealed (6) a behavioural polymor-phism in Mediterranean adults, which included a lack of area Wdelity and connection between distant neritic foraging grounds.
Mediterranean Marine Science
The Adriatic Sea is one of the main foraging areas for marine turtles of the Mediterranean Sea, but the specific high-use sites are poorly known, due to the scarceness of satellite tracking data available for juvenile turtles frequenting the area. In the present study, we tracked 8 juvenile and adult loggerhead turtles (Caretta caretta) that were released along the north-western Adriatic coast after a rehabilitation period having been equipped with Argos-linked satellite transmitters. Tracked turtles displayed quite variable movement patterns, but mostly remained in the north-western Adriatic, especially during the summer months. A marked preference for specific coastal sites was revealed in many turtles, that actively moved towards these specific locations when released south of it or having spent the winter away. Pooling these data with those obtained in previous studies on a further 10 turtles, we highlighted the presence of two main high-use areas, north and south of the Po Rive...
Long-Term Tracking of Adult Loggerhead Turtles (Caretta caretta)in the Mediterranean Sea
Journal of Herpetology, 2013
Three adult-sized Loggerhead Turtles (Caretta caretta), captured incidentally by bottom trawlers, were tracked by satellite in the Mediterranean Sea for a substantial part of their annual cycle, including the period preceding nesting. The three turtles performed longdistance movements that were variable between individuals but shared common features such as seasonal migration. Very prolonged dives (up to over 300 min) were associated with temperature drops to below 188C , likely an overwintering strategy. Our findings integrate recent tracking data on the postnesting migrations of Mediterranean Loggerhead Turtles, documenting the movement patterns made during the poorly known nonreproductive phase.
Bycatch of Loggerhead Turtle (Caretta caretta) in the Italian Adriatic Midwater Pair Trawl Fishery
Frontiers in Marine Science
Despite the fact that Mediterranean loggerhead turtles are listed as "Least Concern" by the International Union for the Conservation of Nature (IUCN), they are among the most threatened marine megafauna worldwide, because of fishery-related incidental captures. The northern central Adriatic Sea is one of the most overfished basins of the Mediterranean Sea and it supports a very valuable marine biodiversity, including sea turtles. This study assesses the spatial and seasonal impact of the northern central Adriatic midwater pair trawl fishery on loggerhead turtle (Caretta caretta) by examining incidental catches recorded between 2006 and 2018 and environmental variables. The model predicted seasonal variation of loggerhead distribution. According to previous studies, data analysis indicates that most bycatch events of loggerhead turtle occurred in the northern Adriatic Sea. The present data confirm that the northern Adriatic may be an important foraging area for loggerhead turtle. They also highlight the urgent need for a better understanding of the interactions between sea turtles and fisheries to develop and apply suitable, ad hoc management measures in critical habitats.
Scientia Marina, 2010
The southern coast of Ionian Calabria was recently recognized as the main nesting area of the loggerhead sea turtle Caretta caretta in Italy. The aim of this study was to characterize the fishing fleet in this area in terms of number of boats, economic situation, social aspects and impact on sea turtle specimens and target species. A multidisciplinary approach was essential to understand how the conservation problems of C. caretta are linked to various characteristics of the fishing fleet. Our data showed a vast discrepancy between the official census and the actual number of boats fishing in the area: 87% of the observed artisanal vessels lacked a required registration number, and thus were fishing illegally. This has caused serious social problems that worsened over the summer of 2007, when the presence of non-local registered vessels, using drift nets, generated a spatial conflict with the local artisanal fishermen. We identified 11 fishing gears used in the area and four of them were studied with on board observations: illegal drift nets, trammel nets, bottom longlines and longlines targeting swordfish. The total number of turtles caught during the summer in the area by longliners targeting swordfish was calculated to be 500 (±180 SE). In addition the presence of drift netters had a negative impact from an ecological and social point of view. RESUMEN: Actividad pesquera e impacto en la principal área de nidificación de la tortuga boba Caretta Caretta en Italia: diferencia abrumadora con los datos oficiales. -La costa sureste de la Calabria jónica ha sido identificada recientemente como el área principal de nidificación de la tortuga boba Caretta caretta en Italia. El objetivo del presente estudio fue caracterizar la flota pesquera en esta área cuantificando el número de barcos por tipología de pesca y describiendo la situación económica, los aspectos sociales y los impactos sobre individuos de tortugas marinas y de las especies objetivo. El enfoque multidisciplinario ha sido fundamental a la hora de entender como los problemas de conservación de C. caretta se relacionan con las varias características de la flota pesquera. Nuestros datos revelan una enorme discrepancia entre el censo oficial y el número real de barcos que faenan en esta área: el 87% de los barcos artesanales pesca ilegalmente, ya que no poseen la matrícula reglamentaria. Esto causa graves problemas sociales que empeoraron durante el verano 2007, cuando la presencia en el área de barcos matriculados, procedentes de otros lugares y que utilizaban las redes de deriva, provocó un serio conflicto espacial con los pescadores artesanales locales. Identificamos 11 artes de pesca empleadas en el área, cuatro de ellas estudiadas con observaciones a bordo: red de deriva ilegal, trasmallo, palangre de fondo y palangre para la captura del pez espada. El total de tortugas capturadas en verano en el área por los palangreros de pez espada fue estimado en 500 (±180 SE) y la presencia de rederos de deriva tuvo un impacto negativo desde un punto de vista ecológico y social.
Marine Biology, 2005
An aerial survey was conducted in early spring 2002 over the continental shelf of the Balearic Archipelago to study the distribution of neritic loggerhead turtles. Furthermore, five juvenile loggerhead turtles [straight carapace length (SCL) range 37.1-48.7 cm], were instrumented with transmitters and monitored during 2003 by satellite tracking to study habitat use over a broader geographical range. The distribution of the turtles over the continental shelf matched habitat availability, as defined by depth. However, those tracked by satellite spent most of the time in the oceanic waters of the Algerian basin and generally avoided continental shelf areas. In these turtles, average speed of travel and mean cosine of turning angle did not significantly differ between habitats, indicating that avoidance of shelf areas is not due to active habitat selection. On average, tracked turtles spent 35.1±19.7% of the time at the surface, although surface time was much greater in the turtle with the shortest carapace length, suggesting that this individual had limited swimming capacity. We conclude that the transition between passive drifting and active habitat selection occurs at an SCL of about 40 cm. The turtles followed tracks that matched prevailing currents, but on some occasions they also swam upstream. Hence, the distribution of late juvenile log-gerhead turtles in the southern and central western Mediterranean may reflect a combination of passive drifting and active habitat selection.
Aquatic Conservation: Marine and Freshwater Ecosystems, 2012
1. Identifying highly frequented areas is a priority for sea turtle conservation. Although juveniles represent the bulk of the population, a minority of studies have investigated their movement patterns. 2. Six large juvenile loggerhead turtles that were found and released in an important foraging ground in the Mediterranean, the Tunisian continental shelf were tracked. Tracking data were obtained via satellite for periods ranging from 120 to 225 days and allowed the identification of high use areas. 3. All turtles generally performed apparently non-directed, wandering movements in waters with a wide range of seafloor depths. They showed clear residential behaviour to the region with no evident seasonal pattern. Core areas of residence were in the neritic zone or on the edge of the continental shelf, largely overlapping among individuals, and were much smaller than residential oceanic areas reported elsewhere. 4. When integrated into current knowledge, these results suggest an ecological-behavioural model of a gradual shift from a pelagic-vagile to a benthic-sedentary life style with progressive reduction of home ranges. 5. They also highlight an area of the continental shelf and offshore waters as potential core foraging ground for large juvenile loggerhead turtles in the Mediterranean informing future spatial management for loggerhead turtles.
2008
Sea turtle populations worldwide suVer from reduced survival of immatures and adults due to Wshery bycatch. Unfortunately, information about the whereabouts of turtles outside the breeding habitat is scarce in most areas, hampering the development of spatially explicit conservation plans. In the Mediterranean, recoveries of adult females Xipper-tagged on nesting beaches suggest that the Adriatic Sea and Gulf of Gabès are important foraging areas for adults, but such information could be heavily biased (observing and reporting bias). In order to obtain unbiased data, we satellite-tracked seven loggerhead sea turtles after they completed nesting in the largest known Mediterranean rookery (Bay of Laganas, Zakynthos, Greece). Three females settled in the north Adriatic Sea, one in the south Adriatic Sea and two in the Gulf of Gabès area at the completion of their post-nesting migrations (one individual did not occupy a distinct foraging area). The concordance of tracking results with information from recoveries of Xipper-tagged turtles suggests that the north Adriatic Sea and the Gulf of Gabès represent key areas for female adult Mediterranean loggerhead sea turtles.
Marine Biology, 2007
Sea turtle tagging carried out in Italy in the period 1981-2006 resulted in 125 re-encounters of loggerhead turtles (Caretta caretta) after a mean of 2.5 years, from diVerent marine areas in the Mediterranean. At Wrst Wnding, turtles ranged 25-83 cm of curved carapace length. Data were analyzed according to size, area, habitat type, season, in order to provide indication of movement patterns. When integrated with other information, results indicate that: (1) a part of turtles in the oceanic stage show a nomad behavior with movements among diVerent oceanic areas; (2) another part show Wdelity to an oceanic area; (3) turtles in the neritic stage show Wdelity to neritic areas, and once settled to one area, change to other neritic areas is unlikely; (4) nomad oceanic turtles are signiWcantly larger than sedentary ones, and also larger than turtles found in neritic areas; it is hypothesized that these could be Atlantic turtles that eventually leave the Mediterranean; (5) ecological transition from oceanic to neritic habitats occurs at a wide range of sizes, and some turtles may have a very brief oceanic stage; (6) turtles in the oceanic stage are more likely to recruit to neritic areas close to their oceanic areas than to distant ones; (7) part of turtles from some Mediterranean nesting beaches might frequent a relatively limited area range, including both oceanic and neritic areas; (8) in most of the Mediterranean, latitudinal seasonal migrations are unlikely. A general model of movement patterns of loggerhead turtles in the Mediterranean is proposed. Communicated by R. Cattaneo-Vietti.
ICES Journal of Marine Science
Assessing sea turtle movements and connectivity among different areas is pivotal to understanding their biology and implementing efficient conservation actions. In the Adriatic Sea, one of the most important sea turtle foraging areas in the Mediterranean, a total of 311 capture–mark–recapture (CMR) records (mostly bycatch) from 294 loggerhead turtles (Caretta caretta) in the period 1984–2021 were analysed. A general fidelity pattern to Adriatic subareas was indicated by a significantly shorter CMR distance than the potential dispersal distance and by the significantly higher proportion of re-encounters in the same area of release than expected. No seasonal pattern was detected between subareas, and shorter re-encounter distances were observed in turtles released and re-encountered in the same season, suggesting different winter and summer residential areas. Results suggest that turtles frequenting the Adriatic can go anywhere in the Mediterranean basin and may exhibit a wandering be...