Historic species records of the families Onuphidae and Eunicidae, from the Falkland Islands region, are reviewed and updated, new records added from intertidal and nearshore localities on and around the Falkland Islands, and a new species of Hyalinoecia described. Eight genera are reported from around the region including eight taxa of Onuphidae and two of Eunicidae, although most are only known from deep offshore waters. Kinbergonuphis dorsalis is re-described from type material, Kinbergonuphis sp. from the Falkland Islands is described and discrepancies between the two descriptions are examined. Hyalinoecia falklandica sp. nov. is described and the history of the genus and its misidentification in the region is discussed. The new species is distinguished from all other species in the genus through a combination of simple, unidentate falcigers on chaetigers 1 and 2, ventral cirri present to chaetigers 3 or 4, and branchiae present from chaetigers 26 or 27 to the end of the body. The historic record of Marphysa aenea from the Falkland Islands is also shown to be a misidentification and the actual, as-yet-undetermined species present is described. Problems surrounding a correct identification of Marphysa species, other species that do not quite fit current descriptions, and additional Eunicoidea taxa that might be expected to occur in the region are also discussed.

The Falkland Shelf is a highly productive ecosystem in the Southwest Atlantic Ocean. It is characterized by upwelling oceanographic dynamics and displays a wasp-waist structure, with few intermediate trophic-level species and many top predators that migrate on the shelf for feeding. One of these resident intermediate trophic-level species, the Patagonian longfin-squid Doryteuthis gahi, is abundant and plays an important role in the ecosystem. We used two methods to estimate the trophic structure of the Falkland Shelf food web, focusing on the trophic niche of D. gahi and its impacts on other species and functional groups to highlight the importance of D. gahi in the ecosystem. First, stable isotope measurements served to calculate trophic levels based on an established nitrogen baseline. Second, an Ecopath model was built to corroborate trophic levels derived from stable isotopes and inform about trophic interactions of D. gahi with other functional groups. The results of both methods placed D. gahi in the centre of the ecosystem with a trophic level of ~ 3. The Ecopath model predicted high impacts and therefore a high keystoneness for both seasonal cohorts of D. gahi. Our results show that the Falkland Shelf is not only controlled by species feeding at the top and the bottom of the trophic chain. The importance of species feeding at the third trophic level (e.g. D. gahi and Patagonotothen ramsayi) and observed architecture of energy flows confirm the ecosystem's wasp-waist structure with middle-out control mechanisms at play.

The continental margin off the La Plata Estuary (SE South America) is characterized by high fluvial sediment supply and strong ocean currents. High-resolution sediment-acoustic data combined with sedimentary facies analysis, AMS-14C ages, and neodymium isotopic data allowed us to reconstruct late Quaternary sedimentary dynamics in relation to the two major sediment sources, the La Plata Estuary and the Argentine margin. Sediments from these two provinces show completely different dispersal patterns. We show that the northward-trending La Plata paleo-valley was the sole transit path for the huge volumes of fluvial material during lower sea levels. In contrast, material from the Argentine margin sector was transported northwards by the strong current system. Despite the large sediment volumes supplied by both sources, wide parts of the shelf were characterized by either persistent non-deposition or local short-term depocenter formation. The location and formation history of these depocenters were primarily controlled by the interplay of sea level with current strength and local morphology. The high sediment supply was of secondary importance to the stratigraphic construction, though locally resulting in high sedimentation rates. Thus, the shelf system off the La Plata Estuary can be considered as a hydrodynamic-controlled end-member.

Argentina is one of the countries with the largest overall landings of skates and rays(24 000 t/year). As a consequence of high levels of exploitation and deficient managementtools, many of these species are threatened with extinction. In the bottom trawl fisheryof San Matías Gulf, northern Patagonia, skates and rays are caught as bycatch and all havehistorically been recorded in the fishery logbook under the category “rays”. Therefore,species composition and their characteristics were unknown. The aim of this study was tocharacterize the commercial exploitation of batoid species in this fishery. Our resultsindicate that commercial landings include nine species of skate, six of which are common.Among these, Atlantoraja platana, Sympterygia bonapartiiand Dipturus chilensis were considered the main species of thisfishery. Their combined relative abundance and weight made up about 90% of the batoidcatch throughout the year. Sexual segregation was detected in four species in whichindividuals of one sex dominated commercial landings. The commercial fraction was composedof individuals with a wide range of sizes. Immature individuals could represent 90% of theindividuals landed for some species. At present, lack of data prevents us from quantifyingthe impact that this fishery is having on these species, but our findings highlight theimportance of conducting research surveys to assess the abundance and geographic extent ofthese populations. The information presented here provided the basis for the proposal of anew logbook format incorporating species-level identification. The new logbook wasimplemented on 1 January 2010.

Monthly variations in spatial and depth distributions, sex ratios, and maturity status in two species of hakes, Merluccius hubbsi and M. australis, were analysed in an area where their ranges overlap spatially on the shelf and slope around the Falkland Islands, and in international waters at 45–47° S (High Seas), using data collected by scientific observers on commercial fishing vessels. A variety of exploratory analyses were carried out on the raw data before patterns were quantified using generalised additive models. Both species use the areas studied as their feeding grounds. M. australis occur mainly on the Falkland shelf south of 51° S, whereas M. hubbsi is widely distributed throughout both the Falkland and High Seas shelf areas. Preliminary schemes of the seasonal migrations of both hakes in Falkland waters and on the High Seas are suggested and discussed. M. hubbsi and M. australis are found to be boldly segregated, both spatially and temporally, on their common feeding grounds, thus avoiding potential inter-specific competition for food resources.