Habitat use and spatial fidelity of male South American sea lions during the nonbreeding period

Conditions experienced during the nonbreeding period have profound long-term effects on individual fitness and survival. Therefore, knowledge of habitat use during the nonbreeding period can provide insights into processes that regulate populations. At the Falkland Islands, the habitat use of South American sea lions (Otaria flavescens) during the nonbreeding period is of particular interest because the population is yet to recover from a catastrophic decline between the mid-1930s and 1965, and nonbreeding movements are poorly understood. Here, we assessed the habitat use of adult male (n = 13) and juvenile male (n = 6) South American sea lions at the Falkland Islands using satellite tags and stable isotope analysis of vibrissae. Male South American sea lions behaved like central place foragers. Foraging trips were restricted to the Patagonian Shelf and were typically short in distance and duration (127 ± 66 km and 4.1 ± 2.0 days, respectively). Individual male foraging trips were also typically characterized by a high degree of foraging site fidelity. However, the isotopic niche of adult males was smaller than juvenile males, which suggested that adult males were more consistent in their use of foraging habitats and prey over time. Our findings differ from male South American sea lions in Chile and Argentina, which undertake extended movements during the nonbreeding period. Hence, throughout their breeding range, male South American sea lions have diverse movement patterns during the nonbreeding period that intuitively reflects differences in the predictability or accessibility of preferred prey. Our findings challenge the long-standing notion that South American sea lions undertake a winter migration away from the Falkland Islands. Therefore, impediments to South American sea lion population recovery likely originate locally and conservation measures at a national level are likely to be effective in addressing the decline and the failure of the population to recover

Diving efficiency at depth and pre-breeding foraging effort increase with haemoglobin levels in gentoo penguins

Individual differences in oxygen storage and carrying capacity have been associated with fitness-related traits and, for air-breathing aquatic animals, to diving ability and foraging success. In winter, many seabirds must replenish the energy reserves they have depleted during the breeding period. Thus, winter foraging efficiency can influence their upcoming breeding behaviour. Using gentoo penguins Pygoscelis papua as a study species, we investigated (1) if inter-individual variation in diving efficiency (proportion of time spent at the bottom) is associated with indices of oxygen storage and carrying capacity (haemoglobin, haematocrit, body mass), and (2) if measures of pre-breeding foraging effort (mean trip duration, total time at sea, and vertical distance travelled) are associated with these oxygen indices and breeding status. Haemoglobin was positively correlated with diving efficiency, particularly for deeper dives, and only penguins with high haemoglobin levels frequently dove to depths ≥140 m. Such differences could affect resource access. However, because reaching deep offshore waters likely requires travelling more than foraging nearshore, vertical distance travelled during pre-breeding increased with haemoglobin levels. The relationship with haematocrit was non-linear, suggesting that commonly used analyses may be inappropriate for this index. We found that early-laying penguins spent less time at sea prior to nesting than non-breeding penguins, suggesting that more efficient foragers lay earlier. Given that diving efficiency at depth is linked to aerobic capacity, anthropogenic activities taking place in either nearshore or offshore waters (e.g. shallow-water fisheries, offshore oil rigs) may have differing impacts on individuals. Further understanding these links could help the conservation of diving species

Analysis of the spatio-temporal pattern of Southern blue whiting (Micromesistius australis australis) abundance in the bottom-trawl fisheries in the southwest Atlantic using GIS techniques

Southern blue whiting (Micromesistius australis australis ) inhabits the waters of the Southern Hemisphere, and in the south-west Atlantic Ocean. It is distributed over an area next to the Falkland/Malvinas Islands, where it is commonly the most abundant commercial finfish species. This fish migrates to the outer Falkland shelf and aggregates in dense schools to spawn in August-September in the south-western part of the islands. Feeding concentrations of Southern blue whiting are targeted by specialized surimi vessels until the following March. Southern blue whiting is also taken as an occasional bycatch by finfish trawlers. Fishery and biological information collected by scientific observers aboard commercial Spanish trawlers between 1988 and 2003 were analysed in relation to physical and environmental factors to establish the spatio-temporal pattern of the species. The data included 26 168 commercial hauls of which 4 797 positive (including effort, catches and discards, as well as biological and environmental information). CPUE (Catch Per Unit Effort, kg⋅hr-1) was used as abundance index. The analysis of the general spatio-temporal pattern of fish abundance, and the influence of environmental factors, such as SST, SBT and depth on fish abundance and distribution, was based on correlation, variograms, and time-series maps created using GIS. Mature individuals and more specifically spawning females were recorded mainly in the waters south and south-west of the Islands, between 100 and 200 m isobaths

The spatio-temporal pattern of Argentine shortfin squid (Illex argentinus) abundance in the Spanish bottom-trawl fishery in the southwest Atlantic.

The Argentine shortfin squid (Illex argentinus) is a common neritic species occurring in waters off Brazil, Uruguay, Argentina, and the Falkland/Malvinas Islands in the southwest Atlantic. Illex is the most important cephalopod species in the area and plays a significant role in the ecosystem. It is object of major fisheries using both trawlers (mostly from European countries) and jigging vessels (mainly from Asian countries) and the actual total annual catch could reach up to 700 thousand tons. Fishery and biological information collected by scientific observers aboard commercial trawlers between 1988 and 2003 was analysed in relation to physical and environmental factors to establish the spatio-temporal pattern of the species distribution. The data included 26 168 fishing haul records, of which 11103 were positive. CPUE (Catch Per Unit Effort, kg⋅hr-1) was used as abundance index. The analyses of the general spatio-temporal pattern of fish abundance, and the influence of environmental factors, such as SST, SBT and depth on squid abundance and distribution, was based on correlation, variograms, and time-series maps created using GIS. The areas of the highest densities were found in deep waters of the High Seas between 44.5º S – 47.0º S outside the Argentinean EEZ and to the north-west of the Islands in February–May. The correlations between squid abundance and cloud index at different moon phases were also analyzed

The spatio-temporal pattern of Argentine shortfin squid Illex argentinus abundance in the southwest Atlantic

The Argentine shortfin squid (Illex argentinus) is a common neritic species occurring in waters off Brazil, Uruguay, Argentina, and the Falkland/Malvinas Islands in the southwest Atlantic. Illex argentinus is the most important fished cephalopod species in the area and plays a significant role in the ecosystem. It is object of major fisheries using both trawlers (mostly from European countries) and jigging vessels (mainly from Asian countries) and estimated total annual average catch for the last 15 years (1988-2003) is about 700 000 tons. The present paper aims to develop predictive models of squid abundance in relation to physical and environmental conditions, models that could ultimately be applied to fishery forecasting. Fishery and biological data collected by scientific observers aboard commercial trawlers between 1988 and 2003 were analysed in relation to physical and environmental factors to establish the spatio-temporal pattern of the species’ distribution and quantify the influence of environmental variables (e.g. SST, depth) on local abundance. The data included 26 168 fishing haul records, of which 11 103 were positive for Illex. CPUE (Catch Per Unit Effort, kg h−1) was used as abundance index. The analyses were based on time-series maps created using Geographical Information Systems (GIS). GIS maps showed that highest CPUE values were recorded during the first four months of the year (the Austral summer-autumn), with peak values higher than 5000 kg h−1 mainly located within 42◦ S, 46◦ S and MN (North part of Malvinas/Falkland) areas. Generalised additive models (GAMs) were used to describe variation in Illex argentinus abundance in relation to geographical and environmental variables. The presence/absence (PA) of Illex and its abundance (CPUE) in areas of presence were modelled separately. Predictors retained in the optimal models included SST, latitude, longitude, month, average fishing depth and year. Both models suggest a clear seasonal effect: maximum catchability was found during March (PA model) and the maximum abundances were found during the first quarter of the year (CPUE model). GAM models also demonstrated that higher catches and maturity of squid were related, in general terms, to warmer and deeper water.Abondance spatio-temporelle du calmar Illex argentinus dans l’Atlantique Sud. L’encornet rouge argentin (Illex argentinus) est une espèce néritique commune de l’Atlantique Sud-Ouest présente dans les eaux du Brésil, de l’Uruguay de l’Argentine et des îles Malouines (Falklands). Illex argentinus est la principale espèce de céphalopode exploitée dans cette région où elle joue un rôle majeur dans l’écosystème. L’espèce est pêchée par d’importantes flottilles de chalutiers (principalement de pays européens) et aux turluttes industrielles (de pays asiatiques) pour une production annuelle de 700 000 t en moyenne sur les 15 dernières années (1988-2003). Cet article présente des modèles prédictifs de l’abondance en fonction des facteurs physiques et environnementaux ; modèles qui pourraient à terme être appliqués à la gestion des pêches. Les données de capture et les paramètres biologiques récoltés, grâce à des observateurs embarqués, de 1988 à 2003, ont été analysées en relation avec les facteurs physiques pour préciser les variations spatio-temporelles de répartition et quantifier l’effet de la température et de la profondeur sur l’abondance. Le jeu de données porte sur 26 168 traits de pêche dont 11 103 comportant des captures d’Illex. Les captures par unité d’effort (CPUE en kg h−1) sont utilisées comme indice d’abondance et les analyses utilisent des séries de cartes, créées avec un système d’information géographique (SIG). Les valeurs les plus élevées de CPUE sont enregistrées durant les quatre premiers mois de l’année (l’été et l’automne austral) avec un pic dépassant 5000 kg h−1 localisé entre 42◦ S et 46◦ S dans la partie Nord desMalouines. Les modèles additifs généralisés (GAM) ont servi à décrire les variations d’abondance en fonction des variables géographiques et environnementales. La présence ou l’absence de la ressource est modélisée séparément de l’abondance. Les modèles optimaux retiennent comme variables explicatives la température, la latitude, la longitude, le mois, la profondeur et l’année. Les deux modèles indiquent un effet saisonnier net: la capturabilité est maximale en mars (présence/absence) et l’abondance (CPUE) est la plus élevée durant le premier trimestre. Les modèles additifs généralisés montrent également que les captures les plus élevées d’animaux à maturité sont associées à des eaux plus tièdes et des secteurs plus profonds

Preliminary study of the variations on the spatio-temporal distribution of a potentially exploitable species (Patagonotothen spp.) in the southwest Atlantic, using GIS techniques

The genus Patagonotothen is the most common Nototheniid on the Patagonian Shelf and slope and is part of the by-catch species in the bottom trawl fisheries. This paper presents preliminary results from the EC CRAFT project “Promoting higher added value to a finfish species rejected to sea”, aiming to develop the research and the technology necessary to promote higher added value to fishing activity by taking profit from a finfish species (Rockcod, Patagonotothen spp.) not known to consumers and currently discarded by the EU fishing fleet operating in the South West Atlantic in order to supply the EU seafood industry with a good quality raw material for human food manufacturing. Historical fishery data series (26 168 commercial hauls of which 12 745 were positive), including effort, catches and discards, as well as biological and environmental information, from 1988 onwards was used to describe and quantify patterns and spatio-temporal changes in the rockcod fishery. These data was collected by scientific observers on board commercial vessels.GIS analysis was carried out in order to study the seasonal geographical changes in the distribution of abundance, SST and densities calculated from CPUE. Fishery and environmental data as well as SST data derived from the NOAA Advanced Very High Resolution Radiometer (AVHRR), were analysed in order to find monthly variations in spatial and depth distribution of Patagonotothen spp. Preliminary results demonstrated that, within areas of occurrence, there are significant correlations between fish abundance (CPUE), the oceanographic conditions of the area (SST gradients) and depth in certain months

Marine nutrient subsidies promote biogeochemical hotspots in undisturbed, highly humic estuaries

The land-ocean dissolved organic carbon (DOC) flux represents a significant term within the global carbon budget, with peatland-dominated regions representing the most intense sources of terrestrial DOC export. As the interface between freshwater and marine systems, estuaries have the potential to act as a filter of the land-ocean carbon flux, removing terrestrially derived DOC, which is present at low concentrations in the oceans, via a combination of physicochemical and biological processes. However, the fate of peat-derived DOC within estuaries remains poorly quantified, partly due to the complicating influences of heterogeneous soils, land-use, point sources, and upstream modification of organic matter. To minimize these modifying factors, we studied DOC and inorganic nutrients in four small, peat-dominated, minimally disturbed, and oligotrophic Falkland Island estuaries. Contrary to expectations, we found limited evidence of physicochemical estuarine DOC removal, and instead observed apparent “hot zones” of biogeochemical activity, where terrestrially-derived silicate mixed with inorganic nitrogen and phosphorus entering the estuaries from the nutrient-rich marine ecosystem. In two estuaries, this coincided with apparent in situ DOC production. We suggest that the observed phenomena of marine nutrient subsidy of estuarine productivity, and flexible utilization of multiple nutrients within the oligotrophic system, may once have been widespread in temperate estuaries. However, this function has been lost in many ecosystems due to catchment eutrophication by agricultural and urban development. We conclude that the estuaries of the Falkland Islands provide a valuable pre-disturbance analogue for natural biogeochemical functioning in temperate estuaries receiving high organic matter inputs

Mismatches in scale between highly mobile marine megafauna and marine protected areas

Marine protected areas (MPAs), particularly large MPAs, are increasing in number and size around the globe in part to facilitate the conservation of marine megafauna under the assumption that large-scale MPAs better align with vagile life histories; however, this alignment is not well established. Using a global tracking dataset from 36 species across five taxa, chosen to reflect the span of home range size in highly mobile marine megafauna, we show most MPAs are too small to encompass complete home ranges of most species. Based on size alone, 40% of existing MPAs could encompass the home ranges of the smallest ranged species, while only \u3c 1% of existing MPAs could encompass those of the largest ranged species. Further, where home ranges and MPAs overlapped in real geographic space, MPAs encompassed \u3c 5% of core areas used by all species. Despite most home ranges of mobile marine megafauna being much larger than existing MPAs, we demonstrate how benefits from MPAs are still likely to accrue by targeting seasonal aggregations and critical life history stages and through other management techniques

Albatrosses Following Fishing Vessels: How Badly Hooked Are They on an Easy Meal?

Fisheries have major impacts on seabirds, both by changing food availability and by causing direct mortality of birds during trawling and longline setting. However, little is known about the nature and the spatial-temporal extent of the interactions between individual birds and vessels. By studying a system in which we had fine-scale data on bird movements and activity, and near real-time information on vessel distribution, we provide new insights on the association of a threatened albatross with fisheries. During early chick-rearing, black-browed albatrosses Thalassarche melanophris from two different colonies (separated by only 75 km) showed significant differences in the degree of association with fisheries, despite being nearly equidistant to the Falklands fishing fleet. Most foraging trips from either colony did not bring tracked individuals close to vessels, and proportionally little time and foraging effort was spent near ships. Nevertheless, a few individuals repeatedly visited fishing vessels, which may indicate they specialise on fisheries-linked food sources and so are potentially more vulnerable to bycatch. The evidence suggests that this population has little reliance on fisheries discards at a critical stage of its nesting cycle, and hence measures to limit fisheries waste on the Patagonian shelf that also reduce vessel attractiveness and the risk of incidental mortality, would be of high overall conservation benefit