Seabirds as indicators of marine resources:black-browed albatrosses feeding on ommastrephid squids in Kerguelen waters

The species, distributions and abundances of squids in the Southern Ocean are difficult to assess by conventional oceanographic means. The study of the food and feeding ecology of squid-eating predators such as procellariiform seabirds appears to be a supplemental way to collect useful information on cephalopod biology. Regurgitations were collected from 52 chicks of the black-browed albatross Diomedea melanophrys at Kerguelen Island in February 1994. Cephalopod remains were removed and identified by means of beaks, gladius and mantle. Squid beaks of the family Ommastrephidae amounted to 55 % (n = 348) of the accumulated squid beaks. They were also those most often regurgitated in association with partially digested crowns and mantles (90 % of the squid fresh remains, n = 28). Two species of ommastrephids equally dominated the squid diet, Martialia hyadesi (only found once in Kerguelen waters) and a Todarodes species, probably T. angolensis, previously unknown in the area. The concomitant satellite tracking of 16 adult birds over a total of 35 foraging trips identified their main feeding areas as the inner shelf break to the NE and over a bank to the SE of Kerguelen Island. Taken together, albatross dietary and foraging data indicate that juveniles of M. hyadesi and Todarodes sp, concentrate over the upper shelf slope to the east of Kerguelen Island, some of them occurring in the top 5 m of the water column where they are caught by the albatrosses

Isotopic Investigation of Contemporary and Historic Changes in Penguin Trophic Niches and Carrying Capacity of the Southern Indian Ocean

A temperature-defined regime shift occurred in the 1970s in the southern Indian Ocean, with simultaneous severe decreases in many predator populations. We tested a possible biological link between the regime shift and predator declines by measuring historic and contemporary feather isotopic signatures of seven penguin species with contrasted foraging strategies and inhabiting a large latitudinal range. We first showed that contemporary penguin isotopic variations and chlorophyll a concentration were positively correlated, suggesting the usefulness of predator δ13C values to track temporal changes in the ecosystem carrying capacity and its associated coupling to consumers. Having controlled for the Suess effect and for increase CO2 in seawater, δ13C values of Antarctic penguins and of king penguins did not change over time, while δ13C of other subantarctic and subtropical species were lower in the 1970s. The data therefore suggest a decrease in ecosystem carrying capacity of the southern Indian Ocean during the temperature regime-shift in subtropical and subantarctic waters but not in the vicinity of the Polar Front and in southward high-Antarctic waters. The resulting lower secondary productivity could be the main driving force explaining the decline of subtropical and subantarctic (but not Antarctic) penguins that occurred in the 1970s. Feather δ15N values did not show a consistent temporal trend among species, suggesting no major change in penguins’ diet. This study highlights the usefulness of developing long-term tissue sampling and data bases on isotopic signature of key marine organisms to track potential changes in their isotopic niches and in the carrying capacity of the environment

Pygmy Sperm Whale (Kogin breiJiceps) stranding record in Tasmania, Australia, and diet of a single specimen

This study describes the stranding record of the Pygmy Sperm Whale, Kogia breviceps, in Tasmanian waters, and the diet of a single individual. The Pygmy Sperm Whale is one of the most commonly stranded cetaceans in some parts of Australia, although it occurs infrequently in the Tasmanian stranding record, with only seven known stranding events. Dietary items were investigated from a single juvenile male Pygmy Sperm Whale stranded in southeast Tasmania. The recoverable diet consisted of approximately three kilograms of reconstructed cephalopod prey mass from at least 11 cephalopod species within nine families. Using reconstructed biomass, the most important family was Histioteuthidae (Histioteuthis atlantica and H. miranda: 29% of reconstructed biomass), followed by Ommastrephidae (unknown sp.: 27% of reconstructed biomass), Enoploteuthidae (Enoploteuthis sp): 25% of reconstructed biomass), Cranchiidae (Cranchia scabra and Teuthowenia pellucida), Chiroteuthidae (Chiroteuthis veranyi), Brachioteuthidae (Brachioteuthis linkovskyi), Neoteuthidae (Nototeuthis dimegacotyle), Pyroteuthidae (Pyroteuthis margaritifera) and Sepiolidae (Heteroteuthis sp.). Collection and analysis of biological material from Pygmy Sperm Whale strandings around Australia should be a high priority to better understand the ecology of this poorly known species

Trace elements in invertebrates and fish from Kerguelen waters, southern Indian Ocean

International audienceGiven the lack of background data on essential and non-essential trace elements in invertebrates and fish known to be the predominant prey of marine mammals and seabirds breeding at the Kerguelen Islands, this study intends to provide these results of great influence for predators in higher trophic levels. To this end, plankton organisms (9 species/4 phyla), mollusks (2 bivalves and 2 squid species) and fishes (8 benthic and 10 pelagic species) from Kerguelen waters were analysed for cadmium (Cd), copper (Cu), mercury (Hg), and zinc (Zn). Individual concentrations of non-essential elements (particularly Cd) showed larger variation in comparison with essential ones due to homeostasis. Cd ranged over 4 orders of magnitude; however, Hg ranged only 1, without significant correlation to trophic level. Instead, ecological parameters (benthic/mesopelagic habitat and feeding ecology) showed a more important influence on the results. Concerning seashore organisms, bivalves collected inside the Gulf of Morbihan had higher Cd concentrations compared to those from the Kerguelen shelf, suggesting a local source of Cd, such as runoff water from bird colonies. Comparison with literature showed metal concentrations in invertebrates and fishes from Kerguelen Islands somewhat lower than in the Antarctic area, with Hg prevailing in benthic species and Cd in pelagic ones. In contrast to Hg, Cd values of squids, jellyfish and the amphipod Themisto gaudichaudii were significantly higher than all other species. Finally, top predators foraging in this area that can be subject to potentially high Hg and Cd exposure through their diet at Kerguelen are reviewed

Texture analysis of magnetic resonance images of rat muscles during atrophy and regeneration

OBJECTIVES: The goals of the current study were (i) to introduce texture analysis on magnetic resonance imaging (MRI-TA) as a noninvasive method of muscle investigation that can discriminate three muscle conditions in rats; these are normal, atrophy and regeneration; and (ii) to show consistency between MRI-TA results and histological results of muscle type 2 fibers\u27 cross-sectional area. METHOD: Twenty-three adult female Wistar rats were randomized into (i) control (C), (ii) immobilized (I) and (iii) recovering (R) groups. For the last two groups, the right hind limb calf muscles were immobilized against the abdomen for 14 days; then, the hind limb was remobilized only for the R group for 40 days. At the end of each experimental period, MRI was performed using 7-T magnet Bruker Avance DRX 300 (Bruker, Wissembourg); T1-weighted MRI acquisition parameters were applied to show predominantly muscle fibers. Rats were sacrificed, and the gastrocnemius muscle (GM) was excised immediately after imaging. (A) Histology: GM type 2 fibers (fast twitch) were selectively stained using the adenosine triphosphatase (ATPase) technique. The mean cross-sectional areas were compared between the three groups. (B) Image analysis: regions of interest (ROIs) were selected on GM MR images where statistical methods of texture analysis were applied followed by linear discriminant analysis (LDA) and classification. RESULTS: Histological analysis showed that the fibers\u27 mean cross-sectional areas on GM transversal sections represented a significant statistical difference between I and C rats (ANOVA, P<.001) as well as between R and I rats (ANOVA, P<.01), but not between C and R rats. Similarly, MRI-TA on GM transversal images detected different texture for each group with the highest discrimination values (Fisher F coefficient) between the C and I groups, as well as between I and R groups. The lowest discrimination values were found between C and R groups. LDA showed three texture classes schematically separated. CONCLUSION: Quantitative results of MRI-TA were statistically consistent with histology. MRI-TA can be considered as a potentially interesting, reproducible and nondestructive method for muscle examination during atrophy and regeneration

Long-term species, sexual and individual variations in foraging strategies of fur seals revealed by stable isotopes in whiskers

Background: Individual variations in the use of the species niche are an important component of diversity in trophic interactions. A challenge in testing consistency of individual foraging strategy is the repeated collection of information on the same individuals. Methodology/Principal Findings: The foraging strategies of sympatric fur seals (Arctocephalus gazella and A. tropicalis) were examined using the stable isotope signature of serially sampled whiskers. Most whiskers exhibited synchronous delta C-13 and delta N-15 oscillations that correspond to the seal annual movements over the long term (up to 8 years). delta C-13 and delta N-15 values were spread over large ranges, with differences between species, sexes and individuals. The main segregating mechanism operates at the spatial scale. Most seals favored foraging in subantarctic waters (where the Crozet Islands are located) where they fed on myctophids. However, A. gazella dispersed in the Antarctic Zone and A. tropicalis more in the subtropics. Gender differences in annual time budget shape the seal movements. Males that do not perform any parental care exhibited large isotopic oscillations reflecting broad annual migrations, while isotopic values of females confined to a limited foraging range during lactation exhibited smaller changes. Limited inter-individual isotopic variations occurred in female seals and in male A. tropicalis. In contrast, male A. gazella showed large inter-individual variations, with some males migrating repeatedly to high-Antarctic waters where they fed on krill, thus meaning that individual specialization occurred over years. Conclusions/Significance: Whisker isotopic signature yields unique long-term information on individual behaviour that integrates the spatial, trophic and temporal dimensions of the ecological niche. The method allows depicting the entire realized niche of the species, including some of its less well-known components such as age-, sex-, individual- and migration-related changes. It highlights intrapopulation heterogeneity in foraging strategies that could have important implications for likely demographic responses to environmental variability

Current status of using beaks to identify cephalopods: III International Workshop and training course on Cephalopod beaks, Faial island, Azores, April 2007

The identification of cephalopods using their beaks is still a difficult technique. To increase our knowledge of this technique and stimulate a new generation of beak experts, the III International beak workshop and training course was organized in Faial, Azores Islands in 2007. We briefly review the activities of the workshop, including the identification procedure of lower beaks of cephalopods from predators with emphasis on cetaceans, seals, fish and seabirds; provision of basic knowledge to young researchers interested in the study area; identification of recent developments in beak research; and discussion of the main problematic issues. The families that need particular attention are Brachioteuthidae, Chiroteuthidae, Cranchiidae, Cycloteuthidae, Mastigoteuthidae, Octopoteuthidae, Promachoteuthidae, Onychoteuthidae (particularly the genus Walvisteuthis), Mastigoteuthidae and Cirroteuthidae. The stable isotopic signature of beaks is capable of revealing new trophic relationships and migrations. Future work should focus on: a) obtaining more cephalopod material from research cruises; b) promoting a close and continuous collaboration between beak experts and cephalopod taxonomists and; c) developing new, and updated, beak guides