An implementation of Quantitative Fatty Acid Signature Analysis (QFASA) in R. QFASA is a method of estimating the diet composition of predators. The fundamental unit of information in QFASA is a fatty acid signature (signature), which is a vector of proportions describing the fatty acid composition of adipose tissue. Signature data from at least one predator and from samples of all potential prey types are required. Calibration coefficients, which adjust for the differential metabolism of individual fatty acids by predators, are also required. Given those data inputs, a predator signature is modeled as a mixture of potential prey signatures and its diet estimate is obtained as the mixture that minimizes a measure of distance between the observed and modeled signatures. A variety of estimation options, goodness-of-fit diagnostic procedures to assess the suitability of estimates, and simulation capabilities are implemented. Please refer to the package vignette and the documentation files for individual functions for details and references.

This dataset contains fatty acid data expressed as mass percent of total fatty acids from Chukchi Sea polar bears.

In 1992, the Marine Mammal Protection Act established the Marine Mammal Health and Stranding Response Program (Title IV) which operates in support of the Recovered Protected Species goal of NMFS’s Strategic Plan. The Northwest Fisheries Science Center (NWFSC) is the NMFS lead for the biomonitoring components and quality assurance of chemical analyses for the MMHSRP. Information generated by this activity addresses deficiencies in data quality and quantity on the levels of toxic chemical contaminants in marine mammals and their prey, refines methods and approaches for understanding linkages between exposure and specific biological effects and measures, and improves the dissemination of the information to constituents and resource managers. Furthermore, these data will provide a measure of the quality of marine mammal habitats. Various analytical methods developed at the NWFSC will be used for the following marine mammal projects: integrated assessment studies of contaminants and other chemical tracers to assess feeding ecology or population health; monitoring of contaminants from stranded animals in support of studies and from species for which few data exist; continued investigations of potential relationships between contaminant exposure and population effects; participation in Interlaboratory Comparison Exercises conducted by National Institute of Standards and Technology and other similar entities comparing analytical results for chemical tracers; and development of quality control materials and quality assurance criteria for new analytical methods as they are developed as part of our Quality Assurance Program. The results of the chemical tracer analyses will be summarized in a report that will be sent to the Office of Protected Resources by the 4th quarter of FY18. Concentrations of POPs, polycyclic aromatic hydrocarbons and their metabolites, total lipid and lipid profiles, fatty acids, and stable isotopes in samples derived from marine mammal biopsies and necropsies.

This dataset is from a laboratory study that investigated the effect of temperature and tissue type on fatty acid signatures of Pacific cod and walleye pollock.

These data consist of the fatty acid composition (percent of mass) of adipose tissue samples from polar bears in Alaska's southern Beaufort Sea. Fat biopsy samples were collected from polar bears that were either captured or biopsy darted along the north coast of Alaska or on offshore ice during March, April, or May from 2004 to 2016. The data also include an identification code unique to an individual bear, sex, age class, and the date of sample collection.

This dataset contains lab-measured percent lipid and fatty acid composition data from Pacific walruses harvested in waters near Saint Lawrence Island. Each row indicates data from a single layer from a blubber core sample collected from one body site (flank, rump, or sternum) from one walrus harvested by Native Alaskans during the spring walrus hunts of 2007 - 2010. Blubber cores were divided into two roughly equal depths (inner and outer) and individually characterized. Results are proportion lipid content of the sub-sample mass and proportional abundance of each fatty acid of total fatty acids identified in the sub-sample on a wet-weight basis. Some samples were found to be inadequate due to lack of anatomical landmarks and do not have laboratory values indicated. Some samples are flagged as being incomplete based on notes from the laboratory.

This dataset contains lab-measured percent lipid and fatty acid composition data from Pacific walruses harvested in waters near Saint Lawrence Island. Each row indicates data from a single layer from a blubber core sample collected from one body site (flank, rump, or sternum) from one walrus harvested by Native Alaskans during the spring walrus hunts of 2007 - 2010. Blubber cores were divided into two roughly equal depths (inner and outer) and individually characterized. Results are proportion lipid content of the sub-sample mass and proportional abundance of each fatty acid of total fatty acids identified in the sub-sample on a wet-weight basis. Some samples were found to be inadequate due to lack of anatomical landmarks and do not have laboratory values indicated. Some samples are flagged as being incomplete based on notes from the laboratory.

Fatty acid analysis is a powerful tool in food web research for estimating dietary sources in marine predators. However, the utility of fatty acids as dietary indicators from whole lipid samples, rather than from separate lipid classes, has been questioned. Samples are often collected at a single time point, precluding seasonal dietary comparisons. We investigated variations in the fatty acid composition of structural (phospholipids) and storage lipids (triacylglycerols) of Antarctic krill (Euphausia superba) using fisheries samples obtained over one year. Seasonal variation was observed in fatty acid biomarkers within triacylglycerol and phospholipid fractions of krill. Fatty acids in krill triacylglycerols (thought to better represent recent diet), reflected omnivorous feeding with highest percentages of flagellate biomarkers (18:4n-3) in summer, and diatom biomarkers (16:1n-7c) in autumn, winter and spring. Carnivory biomarkers (∑ 20:1 + 22:1 and 18:1n-9c/18:1n-7c) in krill were greater in autumn. Phospholipid fatty acids were less variable and higher in 20:5n-3 and 22:6n-3, which are essential components of cell membranes. Sterol composition did not yield detailed dietary information, but percentages of the major krill sterol, cholesterol, were significantly higher in winter and spring compared with summer and autumn. Unexpectedly, 18:4n-3 and copepod markers ∑ 20:1 + 22:1 were not strongly associated with the triacylglycerol fraction during some seasons. Krill may mobilise 18:4n-3 to phospholipids for conversion to long chain polyunsaturated fatty acids, which would have implications for its role as a dietary biomarker. For the first time, we demonstrate the dynamic seasonal relationship between specific biomarkers and krill lipid classes.

This dataset contains fatty acid data expressed as mass percent of total fatty acids for several species potentially preyed upon by yellow-billed loons. These data were utilized in a quantitative fatty acid signature analysis to estimate the diet of yellow-billed loons nesting on the Arctic Coastal Plain of Alaska.

This dataset contains fatty acid data expressed as mass percent of total fatty acids for several species potentially preyed upon by yellow-billed loons. These data were utilized in a quantitative fatty acid signature analysis to estimate the diet of yellow-billed loons nesting on the Arctic Coastal Plain of Alaska (Haynes et al. 2015).