scholarly journals Diet composition and trophic levels of marine mammals

1998 ◽  
Vol 55 (3) ◽  
pp. 467-481 ◽  
Author(s):  
D Pauly
Keyword(s):  
Marine Mammals ◽  
Diet Composition ◽  
Trophic Levels

Prey consumption estimates for salmon sharks

2019 ◽  
Vol 70 (6) ◽  
pp. 824 ◽  
Author(s):  
Kaitlyn A. Manishin ◽  
Kenneth J. Goldman ◽  
Margaret Short ◽  
Curry J. Cunningham ◽  
Peter A. H. Westley ◽  
...  
Keyword(s):  
Life History ◽  
Mass Balance ◽  
Marine Mammals ◽  
Extreme Values ◽  
Assimilation Efficiency ◽  
Prey Consumption ◽  
Trophic Levels ◽  
Shark Species ◽  
Top Predators ◽  
Balance Technique

Top predators, such as salmon sharks (Lamna ditropis), can influence the abundance and population structure of organisms at lower trophic levels through direct effects, such as predation mortality, and indirect interactions. As a first step towards better understanding the average annual prey consumption for individual adult salmon sharks, we bracketed consumption estimates using three methods: (1) daily ration requirement; (2) bioenergetic mass balance; and (3) a Bayesian model of shark growth. In the first method, we applied ration estimates for related lamnid shark species that yielded salmon shark estimates of 1461 and 2202kgyear–1. The second method used a mass–balance technique to incorporate life history information from salmon sharks and physiological parameters from other species and produced estimates of 1870, 2070, 1610 and 1762kgyear–1, depending on assumed diet. Growth modelling used salmon shark growth histories and yielded estimates of 16900 or 20800kgyear–1, depending on assumed assimilation efficiency. Of the consumption estimates, those from the mass–balance technique may be the most realistic because they incorporated salmon shark life history data and do not produce extreme values. Taken as a whole, these estimates suggest that salmon sharks have similar energetic requirements to piscivorous marine mammals.

scholarly journals Examining predator–prey body size, trophic level and body mass across marine and terrestrial mammals

2014 ◽  
Vol 281 (1797) ◽  
pp. 20142103 ◽  
Author(s):  
Marlee A. Tucker ◽  
Tracey L. Rogers
Keyword(s):  
Community Structure ◽  
Body Size ◽  
Body Mass ◽  
Marine Environment ◽  
Trophic Level ◽  
Marine Mammals ◽  
Trophic Position ◽  
Trophic Levels ◽  
Predator Prey ◽  
Terrestrial Mammals

Predator–prey relationships and trophic levels are indicators of community structure, and are important for monitoring ecosystem changes. Mammals colonized the marine environment on seven separate occasions, which resulted in differences in species' physiology, morphology and behaviour. It is likely that these changes have had a major effect upon predator–prey relationships and trophic position; however, the effect of environment is yet to be clarified. We compiled a dataset, based on the literature, to explore the relationship between body mass, trophic level and predator–prey ratio across terrestrial ( n = 51) and marine ( n = 56) mammals. We did not find the expected positive relationship between trophic level and body mass, but we did find that marine carnivores sit 1.3 trophic levels higher than terrestrial carnivores. Also, marine mammals are largely carnivorous and have significantly larger predator–prey ratios compared with their terrestrial counterparts. We propose that primary productivity, and its availability, is important for mammalian trophic structure and body size. Also, energy flow and community structure in the marine environment are influenced by differences in energy efficiency and increased food web stability. Enhancing our knowledge of feeding ecology in mammals has the potential to provide insights into the structure and functioning of marine and terrestrial communities.

South American sea lions Otaria byronia as biological samplers of local cephalopod fauna in the Patagonian shelf marine ecosystem

2019 ◽  
Vol 99 (06) ◽  
pp. 1459-1463
Author(s):  
R. L. Bustos ◽  
G. A. Daneri ◽  
E. A. Varela ◽  
A. Harrington ◽  
A. V. Volpedo ◽  
...  
Keyword(s):  
Marine Mammals ◽  
Marine Ecosystem ◽  
Isotopic Signature ◽  
Trophic Levels ◽  
Trophic Relationships ◽  
South American ◽  
Sea Lions ◽  
Patagonian Shelf ◽  
Important Prey ◽  
Top Predators

AbstractCephalopods are important prey in the diet of top predators, such as marine mammals and seabirds. However, detailed information on their trophic relationships in the Patagonian marine ecosystem is scarce, including those cephalopod species with commercial interest. The aims of this study were to evaluate the composition of the cephalopod component in the diet of Otaria byronia and determine the habitat use and trophic levels of their main cephalopod prey by measuring the stable isotopic signature of cephalopod beaks. Between May 2005 and February 2009, fresh faecal samples were collected from two sea lions rookeries in San Matias Gulf. Cephalopods occurred in 39.4% of the 1112 samples collected during the whole period of study. The dominant prey species was Octopus tehuelchus, which occurred in 45.8% of scats containing cephalopod remains, and represented 58.7% in terms of numerical abundance and 52.0% in mass of cephalopods consumed. The second species most consumed was the myopsid Doryteuthis gahi. The significant higher δ15N values of O. tehuelchus beaks in comparison with those of D. gahi showed that these two species have different trophic levels while occupying similar habitat (δ13C values) in neritic waters of the Patagonian shelf.

Omnivory of the larval phantom midge (Chaoborus spp.) and its potential significance for freshwater planktonic food webs

1994 ◽  
Vol 72 (11) ◽  
pp. 2055-2065 ◽  
Author(s):  
Marianne V. Moore ◽  
Norman D. Yan ◽  
Trevor Pawson
Keyword(s):  
Diet Composition ◽  
Trophic Levels ◽  
Potential Significance ◽  
Keratella Cochlearis ◽  
Planktonic Food ◽  
South Central ◽  
Invertebrate Predator ◽  
Asplanchna Priodonta ◽  
Phantom Midge ◽  
Plastic Lake

Developmental and seasonal changes in the preferred prey and the diet composition of the invertebrate predator Chaoborus punctipennis were determined in Plastic Lake, an acidified (pH 5.6) lake in south-central Ontario, Canada. All instars consumed rotifers (mainly Keratella cochlearis, Ploesoma sp., and Asplanchna priodonta), and instars III and IV fed preferentially on crustaceans (mainly bosminids and copepods). Phytoflagellates (Peridinium sp. and Dinobryon sp.), however, numerically dominated the diet of all instars examined (II–IV), and were consumed by instar II larvae in excess of their relative availability. On 40 and 20% of the sampling dates, instars III and IV, respectively, consumed phytoflagellates in accordance with their relative abundance in the lake. Although the contribution of phytoflagellates to the biomass-based diet of C. punctipennis was low, on one occasion phytoflagellates formed almost half of the diet biomass of instar II larvae. A review of the literature shows that in lakes where phytoflagellate densities are high (≥ 100–200/mL), phytoflagellates contribute ≥ 50% of the diet biomass of all instars of Chaoborus spp. These findings indicate that Chaoborus spp. are omnivores that frequently feed on phytoflagellates even when alternative animal prey are abundant. Consumption of phagotrophic phytoflagellates by Chaoborus spp. and other large invertebrate omnivores, such as Mysis spp., Epischura spp., and cyclopoid copepods, may increase the transfer efficiency of organic carbon from the microbial food web to the upper trophic levels in fresh waters. In acidified lakes, consumption of large dinoflagellates by Chaoborus spp. and other invertebrate omnivores may ameliorate the hypothesized bottleneck impeding the flow of carbon between phytoplankton and zooplankton.

scholarly journals Trends of polyfluoroalkyl compounds in marine biota and in humans

2010 ◽  
Vol 7 (6) ◽  
pp. 457 ◽  
Author(s):  
Renate Sturm ◽  
Lutz Ahrens
Keyword(s):  
Marine Mammals ◽  
Emerging Contaminants ◽  
Temporal Trends ◽  
Trophic Levels ◽  
Marine Biota ◽  
Polyfluoroalkyl Compounds ◽  
Phase Out ◽  
Future Work ◽  
Marine Wildlife ◽  
Sulfonyl Fluoride

Environmental context Polyfluoroalkyl compounds are used in a variety of industrial and consumer applications, including polymer production and for surface treatment of textiles and paper. Research over the last 10 years has shown that these compounds are ubiquitous environmental contaminants – they are extremely persistent, show toxic effects and accumulate in the food chain. We evaluate global, temporal and spatial trends of these important emerging contaminants. Abstract This review gives an overview of existing knowledge of polyfluoroalkyl compounds (PFCs) in humans and in marine biota. Temporal trends and spatial distribution of PFCs were globally compared in humans, marine mammals, seabirds and fish. In general, PFC concentrations in the environment have increased significantly from the beginning of the production up to the 1990s. After the phase-out of perfluorooctane sulfonyl fluoride (POSF) production starting in 2000, PFC concentrations in humans generally decreased. In marine biota no clear temporal trends were observed. The temporal trends depended on the species, their trophic levels and the geographical locations. PFC patterns in humans and in marine wildlife species were compared regarding perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), their shorter and longer chain homologues (C4–C15) and precursor compounds. Finally knowledge gaps were identified and recommendations for future work were presented.

scholarly journals Freshwater discharges drive high levels of methylmercury in Arctic marine biota

2015 ◽  
Vol 112 (38) ◽  
pp. 11789-11794 ◽  
Author(s):  
Amina T. Schartup ◽  
Prentiss H. Balcom ◽  
Anne L. Soerensen ◽  
Kathleen J. Gosnell ◽  
Ryan S. D. Calder ◽  
...  
Keyword(s):  
Water Column ◽  
Marine Mammals ◽  
River Mouth ◽  
Ecological Impacts ◽  
Trophic Levels ◽  
Indigenous Populations ◽  
Marine Biota ◽  
Terrestrial Organic Matter ◽  
Water Column Stratification ◽  
Freshwater Inputs

Elevated levels of neurotoxic methylmercury in Arctic food-webs pose health risks for indigenous populations that consume large quantities of marine mammals and fish. Estuaries provide critical hunting and fishing territory for these populations, and, until recently, benthic sediment was thought to be the main methylmercury source for coastal fish. New hydroelectric developments are being proposed in many northern ecosystems, and the ecological impacts of this industry relative to accelerating climate changes are poorly characterized. Here we evaluate the competing impacts of climate-driven changes in northern ecosystems and reservoir flooding on methylmercury production and bioaccumulation through a case study of a stratified sub-Arctic estuarine fjord in Labrador, Canada. Methylmercury bioaccumulation in zooplankton is higher than in midlatitude ecosystems. Direct measurements and modeling show that currently the largest methylmercury source is production in oxic surface seawater. Water-column methylation is highest in stratified surface waters near the river mouth because of the stimulating effects of terrestrial organic matter on methylating microbes. We attribute enhanced biomagnification in plankton to a thin layer of marine snow widely observed in stratified systems that concentrates microbial methylation and multiple trophic levels of zooplankton in a vertically restricted zone. Large freshwater inputs and the extensive Arctic Ocean continental shelf mean these processes are likely widespread and will be enhanced by future increases in water-column stratification, exacerbating high biological methylmercury concentrations. Soil flooding experiments indicate that near-term changes expected from reservoir creation will increase methylmercury inputs to the estuary by 25–200%, overwhelming climate-driven changes over the next decade.

scholarly journals Ecological studies of marine mammals using a seabed-mounted echosounder

2009 ◽  
Vol 66 (6) ◽  
pp. 1029-1036 ◽  
Author(s):  
Lise Doksæter ◽  
Olav R. Godø ◽  
Erik Olsen ◽  
Leif Nøttestad ◽  
Ruben Patel
Keyword(s):  
Marine Mammals ◽  
Principal Component ◽  
Dive Depth ◽  
Trophic Levels ◽  
Target Strength ◽  
Spatial Proximity ◽  
Ecological Studies ◽  
Marine Life ◽  
Deep Scattering Layer ◽  
Temporal And Spatial

Abstract Doksæter, L., Godø, O. R., Olsen, E., Nøttestad, L., and Patel, R. 2009. Ecological studies of marine mammals using a seabed-mounted echosounder. – ICES Journal of Marine Science, 66: 1029–1036. A seabed-mounted, upward-looking, 38 kHz echosounder (Simrad EK60) was used to monitor cetaceans for 128 d between July 2004 and June 2005. The echosounder was placed at 52°N 30°W at a depth of 910 m, in a frontal area with continuous upwelling creating a hotspot of marine life at all trophic levels. Echo tracks were observed, apparently resulting from one or more animals in close temporal and spatial proximity. The 69 “acoustic detections” were examined with a principal component analysis (PCA) considering mean target strength (TS), group size, and maximum dive depth and duration. The PCA conservatively classified 45 of the acoustic detections as “cetaceans”. Their mean TS values varied between −5 and −36 dB, in agreement with earlier TS measurements of whales and dolphins. Several of the supposed cetaceans were apparently feeding in the “deep-scattering layer” when this ascended at night. This study demonstrates that cetacean behaviour, including swimming, feeding, and vocalizing, can be observed and monitored with stationary active-acoustic instrumentation.

scholarly journals Understanding the diet composition of marine mammals: grey seals (Halichoerus grypus) in the Baltic Sea

2010 ◽  
Vol 67 (6) ◽  
pp. 1230-1239 ◽  
Author(s):  
Karl Lundström ◽  
Olle Hjerne ◽  
Sven-Gunnar Lunneryd ◽  
Olle Karlsson
Keyword(s):  
Baltic Sea ◽  
Marine Mammals ◽  
Diet Composition ◽  
Age Groups ◽  
Geographic Region ◽  
Halichoerus Grypus ◽  
The Baltic Sea ◽  
Sampling Condition ◽  
The Baltic ◽  
Sampling Procedures

AbstractLundström, K., Hjerne, O., Lunneryd, S-G., and Karlsson, O. 2010. Understanding the diet composition of marine mammals: grey seals (Halichoerus grypus) in the Baltic Sea. – ICES Journal of Marine Science, 67: 1230–1239. Dietary studies are important in understanding the ecological role of marine mammals and in formulating appropriate management plans in terms of their interactions with fisheries. The validity of such studies has, however, often been compromised by unrepresentative sampling procedures, resulting in false weight being given to external factors seeming to influence diet composition. The bias caused by non-random sampling was examined, using canonical correspondence analysis to assess how the prey species composition in digestive tract samples of Baltic grey seals (Halichoerus grypus) was related to spatial, temporal, and demographic factors and to whether the samples were collected in association with fishing gear or not (“sampling condition”). Geographic region explained the largest fraction of the observed variation, followed by sampling condition, age group, and year. Season and gender were not statistically significant. Segregation of the two age categories “pups” and “juveniles–adults”, and the two geographic categories “Baltic proper” and “Gulf of Bothnia” are proposed to estimate the diet and fish consumption of the Baltic grey seal population as a whole. Atlantic herring was the most commonly recovered prey item in all areas and age groups, followed by European sprat in the south, and common whitefish in the north. Pups had eaten relatively more small non-commercial species than older seals.

scholarly journals Eye fluke infection changes diet composition in juvenile European perch (Perca fluviatilis)

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jenny C. Vivas Muñoz ◽  
Christian K. Feld ◽  
Sabine Hilt ◽  
Alessandro Manfrin ◽  
Milen Nachev ◽  
...  
Keyword(s):  
Diet Composition ◽  
Infection Intensity ◽  
Perca Fluviatilis ◽  
Trophic Levels ◽  
Fish Diet ◽  
European Perch ◽  
Diet Specialization ◽  
Fluke Infection ◽  
Eye Fluke

AbstractIntraspecific diet specialization, usually driven by resource availability, competition and predation, is common in natural populations. However, the role of parasites on diet specialization of their hosts has rarely been studied. Eye flukes can impair vision ability of their hosts and have been associated with alterations of fish feeding behavior. Here it was assessed whether European perch (Perca fluviatilis) alter their diet composition as a consequence of infection with eye flukes. Young-of-the-year (YOY) perch from temperate Lake Müggelsee (Berlin, Germany) were sampled in two years, eye flukes counted and fish diet was evaluated using both stomach content and stable isotope analyses. Perch diet was dominated by zooplankton and benthic macroinvertebrates. Both methods indicated that with increasing eye fluke infection intensity fish had a more selective diet, feeding mainly on the benthic macroinvertebrate Dikerogammarus villosus, while less intensively infected fish appeared to be generalist feeders showing no preference for any particular prey type. Our results show that infection with eye flukes can indirectly affect interaction of the host with lower trophic levels by altering the diet composition and highlight the underestimated role of parasites in food web studies.

scholarly journals Scanning ferry routes: looking for eDNA traces of marine mammals and their preys

2021 ◽  
Vol 4 ◽  
Author(s):  
Elena Valsecchi
Keyword(s):  
Marine Mammals ◽  
High Throughput Sequencing ◽  
Simultaneous Detection ◽  
Environmental Dna ◽  
Trophic Levels ◽  
Systematic Sampling ◽  
Marine Biodiversity ◽  
Tyrrhenian Sea ◽  
Night Time ◽  
Species Specific

Marine environmental DNA (eDNA) surveys are becoming a promising approach to monitor biodiversity status and its variation over time. However, monitoring offshore areas could be extremely costly when using dedicated vessels, beside the impossibility to sample simultaneously geographically distant (even if adjacent) areas. The unexplored possibility of availing on operating ferries as an opportunistic platform for eDNA sampling offers several advantages besides opening limitless opportunities for systematic surveys on marine biodiversity.We present the results of both metabarcoding and barcoding approaches obtained from the analysis of water samples collected on board of a ferry boat along a pilot Mediterranean route crossing the Pelagos Sanctuary for Mediterranean Marine Mammals. The recently described MarVer primer sets (12SrDNA and 16SrDNA regions), specifically designed for the simultaneous detection of marine mammals and other marine vertebrates, were employed. The High Throughput Sequencing (HTS) outcome showed that the markers successfully detected most trophic levels of vertebrate marine communities, and classes, including bony fish, rays, cetaceans and birds. Ferry-based sampling allow to collect sample at any time of the day, and we indeed found diel differences in both quantitative and qualitative distribution of read counts. For instances, we observed an increased abundance of lantern fish amplicons in night-time collect samples (50%), reflecting nocturnal migration through the water column. In general, the number of read counts was significantly higher in nocturnal samples. Such diel differences within our sample indirectly provides evidence of the efficiency of the eDNA approach to detect contemporary signals in the sampled environment. Similarly, cetaceans were detected in correspondence of visual sightings (when these occurred, supplementary samples were collected). Rare species, such as the monk seal, are difficult to be detected in metabarcoding surveys, thus we opted to side the screening of the ferry-samples with a panel of species-specific qPCR assays, which were able to detect DNA traces of the endangered pinniped in the Tuscany archipelago (Tyrrhenian Sea) long before visual observations witnessed its presence in the same area. The study demonstrates the feasibility of using commercial shipping as a platform for eDNA marine sampling without dedicated survey cruises. Commercial shipping routes have potential to act as regular systematic sampling transects which can contribute to evaluating and monitoring marine biodiversity.

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