Daily ration and feeding chronology of dominant diel vertical migrant fishes in the Subtropical Eastern North Atlantic Ocean

[EN] Diel Vertical Migrants (DVMs) are mainly zooplankton and micronekton which migrate upward from 400-500 m depth every night to feed on the productive epipelagic zone, coming back at dawn to the mesopelagic zone, where they defecate, excrete, and respire the ingested carbon. DVMs should contribute to the biological pump in the ocean and, accordingly, to the global CO2 balance. Although those migrants are mainly small fishes, cephalopods and crustaceans, the lanternfishes (myctophidae) usually contribute up to 80% of total DVMs biomass. Thus, myctophids may represent a pathway accounting for a substantial export of organic carbon to the deep ocean. However, the magnitude of this transport is still poorly known. In order to assess this active flux of carbon, we performed a preliminary study of mesopelagic organisms around the Canary Islands. Here we present the results of diet, daily rations and feeding chronology of Lobianchia dofleini, Hygophum hygomii and Ceratoscopelus maderensis, 3 dominant species of myctophids performing diel vertical migrations in the Subtropical Eastern North Atlantic Ocean. Samples were obtained on board the RV La Bocaina during June 2009. Myctophids were sorted and fixed in 4% buffered formalin and the stomach contents of target species were examined and weighted. Feeding chronology was approached by studying stomach fullness and state of digestion of prey items in individuals from hauls performed at different times and depths. Our results provide further information about lanternfishes feeding ecology in relation to their vertical migration patterns as well as their contribution to the biological carbon pump.

Variation in spatial distribution of juvenile loggerhead turtles in the eastern Atlantic and western Mediterranean Sea

[EN] Loggerhead sea turtles (Caretta caretta) originating from the Western Atlantic carry out one of the largest marine migrations, reaching the eastern Atlantic and Mediterranean Sea. It has been proposed that this transatlantic journey is simply a consequence of drifting, with the lack of a target destination and a passive dispersal with oceanic currents. This predicts that the size of the source populations and geographic distance to the feeding grounds should play important roles in defining stock composition in the eastern Atlantic and Mediterranean Sea.

Phenotypically linked dichotomy in sea turtle foraging requires multiple conservation approaches

[EN] Marine turtles undergo dramatic ontogenic changes in body size and behavior, with the loggerhead sea turtle, Caretta caretta, typically switching from an initial oceanic juvenile stage to one in the neritic, where maturation is reached and breeding migrations are subsequently undertaken every 2-3 years [1-3]. Using satellite tracking, we investigated the migratory movements of adult females from one of the world's largest nesting aggregations at Cape Verde, West Africa. In direct contrast with the accepted life-history model for this species [4], results reveal two distinct adult foraging strategies that appear to be linked to body size. The larger turtles (n = 3) foraged in coastal waters, whereas smaller individuals (n = 7) foraged oceanically.

Evaluation of male breeding population inferred from paternity analyses in the Cape Verde islands

[EN] Because of the extensive migrations of marine turtles through the ocean, many aspects of their biology have been unknown for a long time. However, much information has been recently gained from genetic studies and population monitoring of female turtles at their nesting sites. In contrast, still very little is known on the genetic diversity, population structure and dispersal patterns of the male breeding population, mainly because of the difficulty of capturing and monitoring them at sea. The aim of this study is to assess the genetic patterns of the male breeding population of the loggerhead turtle, Caretta caretta, using a non invasive approach and compare them to the female breeding population.

Conservation genetics of North Atlantic loggerhead sea turtles: analysis of nuclear and mitochondrial DNA

[EN] Complex population structure has been described for the loggerhead sea turtle (Caretta caretta), revealing lower levels of population genetic structure in nuclear compared to mitochondrial DNA assays. This may result from mating during spatially overlapping breeding migrations, or male-biased dispersal as previously found for the green turtle (Chelonia mydas). To further investigate these multiple possibilities, we carried out a comparative analysis from twelve newly developed microsatellite loci and the mitochondrial DNA control region (~804 bp) in adult females of the Cape Verde Islands (n=158), and Georgia, USA (n=17).