Trophic Habitat Research Articles

Persistent organic pollutants (POPs) in fish with different feeding habits inhabiting a shallow lake ecosystem

The occurrence of persistent organic pollutants (POPs) in the environment can affect organisms inhabiting aquatic systems, in particular shallow lakes that are vulnerable to environmental stressors. This study aimed to assess POPs accumulation and changes at histological and physiological levels in tissues of three fish species with different trophic habits. Gills, brain, muscle, liver and gonads of Odontesthes bonariensis, Oligosarcus jenynsii and Cyphocharax voga were collected from the shallow lake La Peregrina, located in an agricultural area from Argentina. In addition, contaminant levels in surface water (SW), suspended particulate matter (SPM) and bottom sediments (BS) were assessed. Histological lesions were evaluated in fish tissues and levels of vitellogenin (VTG) were assessed in plasma of male fish in order to correlate these alterations with the presence of POPs in the environment. Organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) were determined by GC-ECD. Biotic and abiotic samples showed the same POPs distribution pattern: OCPs>PCBs>PBDEs. Although tissue distribution of OCPs was species-specific, muscle showed the lowest levels in all species. The most abundant contaminants were endosulfans, suggesting their widespread use in the area. O. bonariensis showed the highest endosulfans levels in liver (184.2–219ngg−1wet w), which was associated with the high SPM levels considering this species is a filter feeder. The occurrence of PCBs and PBDEs shows the ubiquity of these pollutants in the area. Histological lesions in gills and liver of O. bonariensis and O. jenynsii, might be related with the high levels of endosulfans in these organs. The detection of VTG in males warns about a possible exposure to estrogenic compounds in the environment. In conclusion, the simultaneous exposure of fish to multiple environmental pollutants leads to different alterations, so measures should be taken in order to prevent their occurrence and toxic effects.

Trophic habits of mesostigmatid mites associated with bark beetles in Mexico

Trophic habits of mesostigmatid mites associated with bark beetles in Mexico

Warming Ocean Conditions Relate to Increased Trophic Requirements of Threatened and Endangered Salmon

The trophic habits, size and condition of yearling Chinook salmon (Oncorhynchus tshawytscha) caught early in their marine residence were examined during 19 survey years (1981–1985; 1998–2011). Juvenile salmon consumed distinct highly piscivorous diets in cold and warm ocean regimes with major differences between ocean regimes driven by changes in consumption of juvenile rockfishes, followed by several other fish prey, adult euphausiids and decapod larvae. Notable, Chinook salmon consumed 30% more food in the warm versus cold ocean regime in both May and June. Additionally, there were about 30% fewer empty stomachs in the warm ocean regime in May, and 10% fewer in warm June periods. The total prey energy density consumed during the warmer ocean regime was also significantly higher than in cold. Chinook salmon had lower condition factor and were smaller in fork length during the warm ocean regime, and were longer and heavier for their size during the cold ocean regime. The significant increase in foraging during the warm ocean regime occurred concurrently with lower available prey biomass. Adult return rates of juvenile Chinook salmon that entered the ocean during a warm ocean regime were lower. Notably, our long term data set contradicts the long held assertion that juvenile salmon eat less in a warm ocean regime when low growth and survival is observed, and when available prey are reduced. Comparing diet changes between decades under variable ocean conditions may assist us in understanding the effects of projected warming ocean regimes on juvenile Chinook salmon and their survival in the ocean environment. Bioenergetically, the salmon appear to require more food resources during warm ocean regimes.

Respuesta de la biomasa zooplanctónica a los gradientes de estado trófico y precipitación de un embalse tropical

The distribution of the zooplankton biomass in the spatial (longitudinal- vertical) and temporal scales based on the gradients of trophic status, algae biomass and the rainfall was analyzed in the photic zone of the reservoir Riogrande II. Cladocerans dominated the biomass due to the large contribution of Bosmina freyi, followed by copepods and rotifers. Biomass of species of microcrustaceans was associated to the most eutrophic sampling station related to highest algae biomass, whereas biomass of species of rotifers was linked to stations of lower trophic status. Highest biomass of microcrustacean was in the season of greatest trophic status whereas highest biomass of rotifer was related to the strongest rainfall season. In the vertical gradient, lowest biomass of all groups occurred in the subsurface. This zone tended to be avoided by most species during the sampling seasons. The expression of zooplankton biomass in the longitudinal axis and the temporal scale mainly responded to the gradient of trophic status and algae biomass, and in the vertical axis possibly responded to predation. Although, this response did not depend on the trophic habit of the species probably due to the diverse trophic offer of the reservoir and the alimentary plasticity of these species, it was clearly different between microcrustaceans and rotifers.

Avifauna structure in a forest remnant in the North of the State of Rio Grande do Sul, Brazil

The avifauna of a 70-ha forest fragment located in the North of the state of Rio Grande do Sul, southern Brazil was analyzed. The trophic structure, preferential habitats, relative abundance, and frequency of occurrence of the species were studied, with the aim of analyzing the conservation status of the sampled area. Pre-existing trails in the fragment were used as linear transects and they were monthly coursed between October 2012 and September 2013. Hundred-twenty species of birds were recorded; November and December 2012 had the highest bird abundance and species richness. Forty-two species were registered in 25% of the samples and 39 species in 25.1% - 50% of the samples. The trophic categories with highest diversity were insectivorous, omnivorous and frugivorous. The obtained data indicated that the sampling area plays an important role in the conservation of the local avifauna, housing many species with dependence of environments showing low levels of human disturbance. Keywords: abundance, species richness, birds.

The beetle tree of life reveals thatColeoptera survived end‐Permian mass extinction to diversify during theCretaceous terrestrial revolution

AbstractHere we present a phylogeny of beetles (Insecta:Coleoptera) based onDNAsequence data from eight nuclear genes, including six single‐copy nuclear protein‐coding genes, for 367 species representing 172 of 183 extant families. Our results refine existing knowledge of relationships among major groups of beetles. Strepsiptera was confirmed as sister toColeoptera and each of the suborders ofColeoptera was recovered as monophyletic. Interrelationships among the suborders, namelyPolyphaga (Adephaga (Archostemata,Myxophaga)), in our study differ from previous studies. Adephaga comprised two clades corresponding toHydradephaga andGeadephaga. The series and superfamilies ofPolyphaga were mostly monophyletic. The traditionalCucujoidea were recovered in three distantly related clades. Lymexyloidea was recovered withinTenebrionoidea. Several of the series and superfamilies ofPolyphaga received moderate to maximal clade support in most analyses, for exampleBuprestoidea,Chrysomeloidea,Coccinelloidea,Cucujiformia,Curculionoidea,Dascilloidea,Elateroidea,Histeroidea andHydrophiloidea. However, many of the relationships withinPolyphaga lacked compatible resolution under maximum‐likelihood andBayesian inference, and/or lacked consistently strong nodal support. Overall, we recovered slightly younger estimated divergence times than previous studies for most groups of beetles. The ordinal split betweenColeoptera andStrepsiptera was estimated to have occurred in theEarlyPermian. CrownColeoptera appeared in the LatePermian, and only one or two lineages survived the end‐Permian mass extinction, with stem group representatives of all four suborders appearing by the end of theTriassic. The basal split inPolyphaga was estimated to have occurred in theTriassic, with the stem groups of most series and superfamilies originating during theTriassic orJurassic. Most extant families of beetles were estimated to haveCretaceous origins. Overall,Coleoptera experienced an increase in diversification rate compared to the rest ofNeuropteroidea. Furthermore, 10 family‐level clades, all in suborderPolyphaga, were identified as having experienced significant increases in diversification rate. These include most beetle species with phytophagous habits, but also several groups not typically or primarily associated with plants. Most of these groups originated in theCretaceous, which is also when a majority of the most species‐rich beetle families first appeared. An additional 12 clades showed evidence for significant decreases in diversification rate. These clades are species‐poor in theModern fauna, but collectively exhibit diverse trophic habits. The apparent success of beetles, as measured by species numbers, may result from their associations with widespread and diverse substrates – especially plants, but also including fungi, wood and leaf litter – but what facilitated these associations in the first place or has allowed these associations to flourish likely varies within and between lineages. Our results provide a uniquely well‐resolved temporal and phylogenetic framework for studying patterns of innovation and diversification inColeoptera, and a foundation for further sampling and resolution of the beetle tree of life.

Ocean acidification effects on stable isotope signatures and trophic interactions of polychaete consumers and organic matter sources at a CO2 shallow vent system

Stable carbon and nitrogen isotope analysis (SIA) was used to examine trophic interactions in a naturally acidified shallow coastal CO2 area in the Mediterranean Sea. SIA was helpful to determine the potential effects of ocean acidification (OA) on the interactions of organic matter sources and polychaete consumers, which appear to be tolerant to high pCO2. Mesoherbivore consumers, represented by three polychaete species, Platynereis dumerilii (Audouin and Milne Edwards, 1834) (Nereididae), Polyophthalmus pictus (Dujardin, 1839) (Opheliidae) and Syllis prolifera Krohn, 1852 (Syllidae), are abundant in the low pH conditions of the CO2 vents. Samples of consumers and potential organic matter sources (macroalgae, seagrass and epiphytes) were collected in two periods (May-June and Oct-Nov 2012) in two acidified areas (Castello Aragonese CO2 vents, off Ischia, Italy) and in two control areas. Results suggest a substantial effect of high pCO2 on isotopic composition of both organic matter sources and consumers. The recurring 13C depletion observed in the acidified sites is probably due to an increase in carbon availability and to the exploitation of volcanic-derived dissolved inorganic carbon (DIC) present in the area. The nutritional quality of organic matter sources was higher in low pH stations, where indeed C:N ratios decreased. Despite the occurrence of these effects, the trophic habit of high pCO2 tolerant polychaete consumers seems not to be dramatically affected. Our findings shed the light on how some benthic organisms may respond well to near-future OA conditions, exhibiting high plasticity also in their feeding habits, without being subject to dramatic ecological changes.

Functional and Phylogenetic Characterization of Proteins Detected in Various Nematode Intestinal Compartments*[S

The parasitic nematode intestine is responsible for nutrient digestion and absorption, and many other processes essential for reproduction and survival, making it a valuable target for anthelmintic drug treatment. However, nematodes display extreme biological diversity (including occupying distinct trophic habitats), resulting in limited knowledge of intestinal cell/protein functions of fundamental or adaptive significance. We developed a perfusion model for isolating intestinal proteins in Ascaris suum (a parasite of humans and swine), allowing for the identification of over 1000 intestinal A. suum proteins (using mass spectrometry), which were assigned to several different intestinal cell compartments (intestinal tissue, the integral and peripheral intestinal membranes, and the intestinal lumen). A multi-omics analysis approach identified a large diversity of biological functions across intestinal compartments, based on both functional enrichment analysis (identifying terms related to detoxification, proteolysis, and host-parasite interactions) and regulatory binding sequence analysis to identify putatively active compartment-specific transcription factors (identifying many related to intestinal sex differentiation or lifespan regulation). Orthologs of A. suum proteins in 15 other nematodes species, five host species, and two outgroups were identified and analyzed. Different cellular compartments demonstrated markedly different levels of protein conservation; e.g. integral intestinal membrane proteins were the most conserved among nematodes (up to 96% conservation), whereas intestinal lumen proteins were the most diverse (only 6% conservation across all nematodes, and 71% with no host orthologs). Finally, this integrated multi-omics analysis identified conserved nematode-specific intestinal proteins likely performing essential functions (including V-type ATPases and ABC transporters), which may serve as promising anthelmintic drug or vaccine targets in future research. Collectively, the findings provide valuable new insights on conserved and adaptive features of nematode intestinal cells, membranes and the intestinal lumen, and potential targets for parasite treatment and control.

Trophic levels and habitat specialization of beetles caught on experimentally added aspen wood: Does trap type really matter?

Saproxylic (wood living) beetles make up an important part of forest biodiversity and are of importance for conservation practices. The beetles are commonly surveyed on various dead wood resources by use of flight interception traps (window traps), catching both species depending on the resource and vagrant (irrelevant) species. Enclosed traps have been suggested as an alternative sampling method, as they sample only the beetles utilizing the dead wood resource. This is the first study to compare the two trap types based on catches from experimentally added identical wood units. Our main aim was to test whether enclosed window traps catch a higher proportion of specialized species and species of a lower trophic level than open window traps, and whether proportions of vagrant species decrease with habitat specialization and trophic level in both trap types. The study was carried out during two summers with traps mounted on replicated, identical units of fresh aspen dead wood in boreal forest in south-eastern Norway. Contrary to our expectations and earlier findings, the enclosed window traps did not catch a higher proportion of habitat specialists (aspen-associated species) or species at the lowest trophic level (wood feeding) compared to the open traps. Rather, the proportion of predators was higher and fungivores lower in enclosed versus open window traps, and no difference was found between different categories of habitat specialization. The proportion of vagrant species was lowest among the beetles with the strongest specialization (aspen-associated) whereas there was no difference with trophic levels. We suggest that keeping vagrants but selecting species based on host tree affinity is the best way to use catches from open window traps on dead wood units. Studies of predators and fungivores should be interpreted with care.

Short-term responses of wolf feeding habits to changes of wild and domestic ungulate abundance in Northern Italy

Long-term changes of wolf feeding habits have been recorded in several parts of its European range and were related to the increase of wild ungulate populations. An increased use of wild prey often is linked to a decrease of predation on livestock, and consequently it can reduce wolf–human conflict and make for easier predator conservation. We analysed wolf diet from scats collected from 2007 to 2012 in a 927.3-km2 area of the Northern Apennines (Northern Italy) to compare the present diet to that recorded in the late 1980s when the area was colonised by wolves, and to examine short-term changes of wolf feeding habits together with annual and seasonal variations of wild and domestic ungulate selection, possibly related to the increase of wild ungulate abundance. We calculated the availability proportions of wild ungulate species from the presence signs recorded on itineraries and those of livestock species from the data on farms of veterinary services. We identified 17 kinds of prey, pooled into six categories, of which wild ungulates (70%) and livestock (20%) were the most important. During the study period, we observed a reduction in the diet breadth of wolves, to a greater use of wild ungulates, depending on the increase in the availability of wild prey species. Significant seasonal variations were observed in the trophic habits of the wolf, but generally there was a wide use of wild ungulates, especially wild boars. Livestock was mainly used in summer, which corresponds to the period of greatest presence of domestic ungulates on the pastures. Considering the study period, a fast response of wolf feeding habits to the increase of wild ungulate species resulted, together with changes in selection patterns. The change in diet towards a greater use of wild ungulates is an important step in the recovery and conservation of the wolf.

Rarity of blister beetles (Coleoptera: Meloidae) in Southern Africa correlates with their phylogeny and trophic habits, but not body size

Ecologists have identified several correlates of biological rarity in animals. Among the various correlates identified so far, three are explored in this paper: (a) abundance is correlated with absolute body size in animals; (b) phylogenetically primitive taxa are overrepresented in samples of rare species; (c) more specialized species are rarer than less specialized species. Here we use Namibian blister beetles (Coleoptera: Meloidae) as a model system for exploring these issues. We used data from five field expeditions, which resulted in the identification of 891 beetles belonging to 76 species collected from 191 sites. 13% of the species accounted for over 50% of the individuals; 22% of all species were represented by singletons. Abundance patterns differed significantly among the different trophic categories, with non-pollinophagous (non-specialized) species being more abundant than weed-eaters and pollinophagous (specialized) species. Species of phylogenetically basal tribes were less abundant than those of more derived groups. Trophic category and phylogenesis did not have a synergic effect in determining the relative abundance of the species, and body size had no influence on their abundance.

Evidence for a multi-peak adaptive landscape in the evolution of trophic morphology in terapontid fishes

Using the Australian marine-freshwater terapontid fishes as a model system, we examined the role of dietary phenotypic optima in an adaptive macro-evolutionary landscape. Comparative modelling relying on both a priori and data-driven identification of selective regimes suggested multi-peak models as best describing much of the dietary phenotypic landscape of terapontids. Both approaches identified common phenotypic optima for different lineages of marine and freshwater herbivores, and minimal differentiation between carnivores and omnivores, irrespective of their phylogenetic relationships, as the model best describing morphological evolution. Significant correlations also existed between these phenotypic axes and proportions of non-animal dietary items in species' diets. While simulation results provided evidence for a multi-peak adaptive landscape in the evolution of trophic morphology in terapontids, they could not rule out chance convergence in these adaptive peaks. However, they do provide scope for identifying areas for more detailed, functionally specific study of phenotypic convergence in herbivorous terapontid trophic habits.

Ecoregional Vulnerability Assessment for the Functional Richness of South American Carnivorans (Mammalia: Carnivora)

Mapping geographic trends in biodiversity is a key step in conservation planning, which has been mainly focused on taxonomic criteria or species of particular concern. More recently, higher consideration of ecosystem functioning has been advocated, allocating more attention to traits and functional diversity of species assemblages. Carnivorans (Mammalia: Carnivora) are charismatic, albeit threatened, species that variously affect ecosystem functioning through consumptive processes, and whose functional diversity depends on traits associated with their trophic habits and energetic requirements. Yet, analyses of spatial trends in the diversity and vulnerability of carnivoran assemblages have mostly focused on taxonomic and phylogenetic criteria. Then, the present study assessed the vulnerability of the functional richness of South American carnivoran assemblages, both at continental and regional levels. As a first diagnostic of vulnerability, the form of the association between functional richness and species richness (FRS) was assessed through simulations. The resulting nearly linear association indicated low functional redundancy and high sensitivity to global extinctions. A more realistic FRS accounting for actual extinction threats exacerbated losses of functional richness. Further, a positive correlation between effect and response traits suggests non-compensatory responses to environmental stressors by functionally redundant species and, thus, sensitivity of carnivoran functional richness to ongoing trends in land conversion and habitat degradation. Regionally, functional richness paralleled latitudinal gradients in species richness, but vulnerability did not entirely match these variables in space, nor did it risk estimates that accounted for regions’ conservation status. This suggests regional differentiation in conservation priorities, complementing existing taxonomically oriented prioritization schemes.

Non-trophic effects of earthworms on enchytraeids: An experimental investigation

Lumbricids and enchytraeids are two keystone fauna groups strongly responsible for the functioning of detrital food webs in temperate soils but acting at contrasting spatial scales. The relationships between both groups are poorly understood: considering their close kinship and trophic habits as generally microbi-/saprovores, competitive interactions are expected. However, due to engineering activities, various non-trophic earthworm impacts on enchytraeids also play a role, which has never been evaluated. We experimentally simulated and quantitatively estimated the effects of major non-trophic earthworm activities (burrowing, cast deposition, mucus release) and, in addition, of earthworm mortmass decay on the abundance of enchytraeids. Effects of two earthworm species belonging to epigeic (Lumbricus rubellus) and endogeic (Aporrectodea caliginosa) ecological groups were tested.Non-trophic earthworm effects strongly varied (a) between the types of activity (burrowing, casts, mucus), (b) across the soil profile, (c) between the earthworm species. In general, enchytraeids responded positively to earthworm non-trophic activities. Mucus release and burrowing showed usually stronger impacts than cast deposition. The participation of different non-trophic effects in the resulting joint effect (burrowing + casts + mucus) varied with earthworm species and soil horizon. Decomposition of dead earthworms stimulated enchytraeid abundance at lower, but inhibited it at higher mortmass amount.A comparison between enchytraeid responses to live earthworm (integrated trophic and non-trophic activities) and joint non-trophic (burrowing + casts + mucus) impacts allowed an approximate separation of both activity types. Rates of trophic and non-trophic impacts were quantitatively comparable and earthworm species-specific. In particular, L. rubellus and A. caliginosa earthworms rendered adverse (negative and positive, respectively) influence on enchytraeid abundance. It was concluded that the negative effects of live L. rubellus on enchytraeids were primarily related to its trophic activity, whereas the positive effects of live A. caliginosa were strongly connected with its non-trophic activities.

Applications of Self-Organizing Maps for Ecomorphological Investigations through Early Ontogeny of Fish

We propose a new graphical approach to the analysis of multi-temporal morphological and ecological data concerning the life history of fish, which can typically serves models in ecomorphological investigations because they often undergo significant ontogenetic changes. These changes can be very complex and difficult to describe, so that visualization, abstraction and interpretation of the underlying relationships are often impeded. Therefore, classic ecomorphological analyses of covariation between morphology and ecology, performed by means of multivariate techniques, may result in non-exhaustive models. The Self Organizing map (SOM) is a new, effective approach for pursuing this aim. In this paper, lateral outlines of larval stages of gilthead sea bream (Sparus aurata) and dusky grouper (Epinephelus marginatus) were recorded and broken down using by means of Elliptic Fourier Analysis (EFA). Gut contents of the same specimens were also collected and analyzed. Then, shape and trophic habits data were examined by SOM, which allows both a powerful visualization of shape changes and an easy comparison with trophic habit data, via their superimposition onto the trained SOM. Thus, the SOM provides a direct visual approach for matching morphological and ecological changes during fish ontogenesis. This method could be used as a tool to extract and investigate relationships between shape and other sinecological or environmental variables, which cannot be taken into account simultaneously using conventional statistical methods.

Trophic ecology of Saccodon dariensis (Pisces: Parodontidae) in Guatapé River tributaries, Magdalena River Basin, Colombia

ABSTRACTObjective. To study the trophic ecology of Saccodon dariensis in the Peñoles and El Cardal streams, Guatape River mid-basin, Magdalena River Basin, Colombia. Materials and methods. To compare differences in size between individuals from the two streams in terms of hydrologic periods, oral polymorphisms or sexes, an analysis of variance was conducted (ANOVA). Volume percentages, frequency of occurrence and the food importance index (FII) were determined; a principal component analysis (PCA) and an ANOVA was carried out to determine the diet differences between streams, climatic periods, oral polymorphism, sexes and developmental states, as well as a Mann-Whitney pairwise comparison test for each food category. Results. A significant difference was found in size between individuals of the two streams with different oral polymorphism. Algae are the most important food item (FII: 91.9%), followed by Trichoptera and insect remains (FII: 4.3%), and vegetal material (FII: 1.8%). The PCA did not indicate significant differences in diet between streams, climatic periods, oral polymorphisms, sexes or developmental states, but the ANOVA and Mann-Whitney pairwise comparison test indicated differences in oral morphotype, where individuals with a straight mouth consumed more vegetal material. We also observed different proportions in consumption of different algae genera, and increased consumption of insects in ontogeny, this being higher in individuals with a straight mouth. Conclusions. The species is algaevorous. The oral morphotypes of S. dariensis may be related to a trophic polymorphism that confers different trophic habits and differential access to the items that constitute their diet.

Species- and size-related patterns in stable isotopes and mercury concentrations in fish help refine marine ecosystem indicators and provide evidence for distinct management units for hake in the Northeast Atlantic

Abstract Recent European environmental policies argue for the development of indicators of the ecological status of ecosystems that are easy to implement and powerful enough to detect changes quickly. For instance, some indicators that are currently proposed for monitoring foodweb structure and functioning are based on the size of organisms, using size as a proxy for trophic level. However, these indicators do not necessarily accurately reflect the underlying trophic structure and dynamics to follow. Ecological tracers (i.e. chemical parameters measured in consumer tissues to infer the trophic ecology of organisms) may serve as complementary indicators of trophic level, and may also help distinguish different populations of a species when more commonly used methods (e.g. genetic, age determination) present their own limitations. Here, we analysed the potential of muscle δ13C and δ15N values and of muscle mercury (Hg) concentrations to depict size-related trophic habits of different fish species. We expected that intra- and interspecific variation in these ecological tracers could be helpful in refining currently proposed indicators of marine ecosystems, and also help in discriminating management unitsfor some species. Four fish species were selected for their economical and/or ecological importance in the Bay of Biscay (Northeast Atlantic): whiting Merlangius merlangus, European hake Merluccius merluccius, Atlantic horse mackerel Trachurus trachurus and anglerfish Lophius piscatorius. Muscle δ13C and δ15N values segregated the species and enabled us to discriminate species-specific feeding strategies with increasing size of individuals. Fish body size was not always linearly correlated with δ15N or trophic level. In contrast, Hg concentrations and size-related Hg patterns were more similar from species to species. Interestingly, muscle δ15N values together with Hg concentrations segregated the two putative stocks of European hake within the Bay of Biscay. Hence, we propose the combined use of ecological tracers as a promising method for accurately assigning a consumer to a trophic guild, investigating Hg trophodynamics in foodwebs, and helping discriminate distinct ecological populations within a species when defining management units.

Foraging movements and habitat niche of two closely related seabirds breeding in sympatry

As central-place foragers, pelagic seabirds are constrained by spatiotemporal heterogeneity to find productive marine areas and compete for prey. We analysed 97 foraging trips to study the movement and oceanographic characteristics of foraging habitats of two different—yet closely related—species of shearwaters (Scopoli’s shearwater Calonectris diomedea and Cory’s shearwater C. borealis) breeding in sympatry in the Mediterranean. We combined various methodological approaches (GPS-tracking, species distribution modelling and stable isotope analysis) to explore the foraging strategies of these two species. Isotopic results suggested that trophic habits of both shearwater species were similar, mainly based on pelagic fish consumption. Foraging areas of both species were characterized by shallow waters near the colony. Both shearwater species exploited persistent productive marine areas. The foraging areas of the two species broadly overlapped during the incubation period, but during chick-rearing period, Scopoli’s shearwaters apparently foraged in different areas than Cory’s shearwaters.

Erratum to: Does the trophic habitat influence the biochemical quality of the gonad of Octopus vulgaris? Stable isotopes and lipid class contents as bio-indicators of different life-cycle strategies

This study aims to test whether environmental conditions including the trophic habitat and diet impact the biochemical composition of storage organs and affect the nutritional quality of eggs of Octopus vulgaris. Trophic habitat and gonad quality of neighbouring populations off the Portuguese coast, subject to different oceanographic regimes, were compared using the digestive gland and beaks as recorders of trophic and habitat preferences, and gonads as indicators of egg quality. Cholesterol, phospholipids and triacylglycerol content, essential fatty acid (EFA) profile of the digestive gland and stable isotopes, δ15N and δ13C, in the buccal mass flesh and beaks were indicators of the differences in the trophic habitat between populations. For gonad quality, the same bio-indicators were used to identify differences with maturation. The study shows that, although diet influences the EFA profile of the gonads to a certain degree, the main lipid content, phospholipids and cholesterol content in the gonads are not influenced by habitat conditions. This, therefore, suggests that O. vulgaris is able to influence the quality of egg content independent of diet. The species is believed to be an income breeder which attains maturity upon reaching a sufficient condition level, then channelling energy directly from food to gonad development.

Trophic habits of the Ommastrephid squid Illex coindetii and Todarodes sagittatus in the northwestern Mediterranean Sea

Squids Illex coindetii and Todarodes sagittatus were collected from commercial trawls in the NW Mediterranean Sea and their stomach contents were analyzed to describe and compare their feeding habits. Fish, crustaceans and squids were found in the stomach contents of both squid species; however T. sagittatus had a wider trophic spectrum composed by fifteen prey items more than I. coindetii. This difference was attributed to the availability of feeding resources in the water column and the larger size and deeper distribution of T. sagittatus. The index of relative importance showed that the crustacean Pasiphaea multidentata was the most important prey for both squids, and that I. coindetii fed secondly on Anchilomera blossevillei, Pasiphaea sivado and the fish Lestidiops sp., while T. sagittatus fed secondly on Phronima sedentaria and the fish Arctozenus risso. The feeding habits of the two squids varied for two prey items at the size interval between 9.1 and 21cm ML. This difference was due to the presence of the amphipod P. sedentaria and the squid Ancistroteuthis lichtensteinii in the stomach contents of T. sagittatus, which are species with deeper distributions. T. sagittatus larger than 21cm ML preyed on other crustaceans and fish, such as big Pandalidae crustaceans and gadiform fish. Finally, the %FO analysis showed that there were fifteen common prey species in the feeding habits of the two squids, but they did not have the same importance for each squid. I. coindetii fed mainly on Lestidiops sp., Chauliodus sloani and P. multidentata and T. sagittatus fed on A. risso and P. sedentaria. These species correspond to mesopelagic fish, decapod crustaceans and amphipods. This suggests that these species are easy to prey at different levels in the water column, which affects the predation and distribution of I. coindetii and T. sagittatus.