Effects of phylogeny and prey type on fatty acid calibration coefficients in three pinniped species: implications for the QFASA dietary quantification technique

Rosen, David A. S.; Tollit, Dominic J.

doi:10.3354/meps09934

Cited by 45 publications

(59 citation statements)

References 35 publications

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“…In accord with previous studies (Budge et al, 2012;Rosen and Tollit, 2012), overestimating the presence of the item used as prey for CC calculations was also observed. Without questioning the necessity of using CC to compensate for lipid metabolism of the predator, it is important to highlight that the incorrect construction or improper use of CC can lead to poorer estimations.…”

Section: Feeding Trial and Calibration Coefficientssupporting

confidence: 92%

“…The determination of how long these experiments have to last to truly reflect the diet in the predator fat storage tissue is critical (Budge et al, 2006). Several studies have been conducted to determine calibration coefficients for birds and mammals (Iverson et al, 2007;Nordstrom et al, 2008;Rosen and Tollit, 2012;Wang et al, 2010;Williams et al, 2009) but, in regard to fish, only Atlantic salmon has been studied (Budge et al, 2011(Budge et al, , 2012. A careful selection of the predator fat store tissue to use in QFASA has been shown to be of crucial importance (Budge et al, 2006;Iverson, 2009).…”

mentioning

confidence: 98%

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Diet estimation of Paralichthys orbignyanus in a coastal lagoon via quantitative fatty acid signature analysis

Magnone

Bessonart

Rocamora

et al. 2015

Journal of Experimental Marine Biology and Ecology

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Section: Feeding Trial and Calibration Coefficientssupporting

confidence: 92%

mentioning

confidence: 98%

Diet estimation of Paralichthys orbignyanus in a coastal lagoon via quantitative fatty acid signature analysis

Magnone

Bessonart

Rocamora

et al. 2015

Journal of Experimental Marine Biology and Ecology

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“…Future studies, including continued harvest-based monitoring of the Mackenzie Estuary beluga harvest (Bell and Harwood, 2012), are important to continue to monitor the trends we have observed. To infer dietary change, these studies could be coupled with diet profiling studies using fatty acids (e.g., Dahl et al, 2000;Theimann et al, 2008) and stable isotopes (Kelly, 2000;Chambellant et al, 2012), provided that appropriate calibration coefficients could be determined (Rosen and Tollit, 2012). Such studies in turn would contribute to our understanding of feeding strategies and eventually provide a quantitative assessment of the time and location of resources selected by belugas throughout their range.…”

Section: Discussionmentioning

confidence: 99%

An Emerging Pattern of Declining Growth Rates in Belugas of the Beaufort Sea: 1989–2008

Harwood¹,

Kingsley²,

Smith³

2014

ARCTIC

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ABSTRACT. Standardized, hunter-based sampling of harvested beluga whales was initiated in the three main harvesting areas of the Mackenzie River delta (Shallow Bay, Kendall Island, Kugmallit Bay) in 1980 and near Paulatuk, Northwest Territories, in 1989. Standard length and sex of landed whales have been recorded for 90 to 110 belugas per year since 1980, and ages have been determined since 1988. Hunters select larger and older belugas; males outnumbered females 2.0 to 1 between 1980 and 1989, 3.0 to 1 between 1990 and 1999, and 3.6 to 1 between 2000 and 2009. Age classes younger than 10 growth layer groups (GLGs) were essentially absent from harvests both in the Delta and near Paulatuk. Asymptotic lengths, calculated using GLG counts from teeth of 839 males and 225 females sampled over 16 seasons (1989, 1993 -2008), were 435.3 cm (SE 2.0) for males and 380.1 cm (SE 1.8) for females. Males were 14.5% longer than females. Belugas landed in the Delta and Paulatuk were mainly mature adults (by hunter selection). Mature belugas landed by Paulatuk hunters were younger and shorter than those taken in the Delta because of age and sex segregation in the hunting areas. There was no difference in the size-at-age relationships for belugas landed at Paulatuk vs the Delta. The linear trend in size-at-age indicated a decline of 0.08% (SE 0.038%) per year, or 1.75% over the 19 year time series. The 314 male belugas landed in the Delta between 2000 and 2007 showed statistically significant differences in blubber thickness among years, but only a slight downward trend over this short period. Mean blubber was thickest in 2002 and 2003 and thinnest in 2005. The thinness of belugas in 2005, and subtle changes in growth of the belugas over the time series, may reflect ecosystem changes that have reduced the availability or quality and quantity of their prey in recent years. Further research, including isotope and fatty acid profiling, would be helpful in substantiating the declining trend in growth and elucidating the causative factors.

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“…To handle this, Iverson et al [8] introduced calibration factors and we accordingly also calibrate the FAs before estimating the diet. A discussion of the calibration factors used in our analysis may be found in [17].…”

Section: Datamentioning

confidence: 99%

An approach to measure distance between compositional diet estimates containing essential zeros

Stewart

2016

Journal of Applied Statistics

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For many applications involving compositional data, it is necessary to establish a valid measure of distance, yet when essential zeros are present traditional distance measures are problematic. In quantitative fatty acid signature analysis (QFASA), compositional diet estimates are produced that often contain many zeros. In order to test for a difference in diet between two populations of predators using the QFASA diet estimates, a legitimate measure of distance for use in the test statistic is necessary. Since ecologists using QFASA must first select the potential species of prey in the predator's diet, the chosen measure of distance should be such that the distance between samples does not decrease as the number of species considered increases, a property known in general as subcompositional coherence. In this paper we compare three measures of distance for compositional data capable of handling zeros, but not satisfying some of the well-accepted principles of compositional data analysis. For compositional diet estimates, the most relevant of these is the property of subcompositionally coherence and we show that this property may be approximately satisfied. Based on the results of a simulation study and an application to real-life QFASA diet estimates of grey seals, we recommend the chi-square measure of distance. ARTICLE HISTORY

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Effects of phylogeny and prey type on fatty acid calibration coefficients in three pinniped species: implications for the QFASA dietary quantification technique

Cited by 45 publications

References 35 publications

Diet estimation of Paralichthys orbignyanus in a coastal lagoon via quantitative fatty acid signature analysis

Diet estimation of Paralichthys orbignyanus in a coastal lagoon via quantitative fatty acid signature analysis

An Emerging Pattern of Declining Growth Rates in Belugas of the Beaufort Sea: 1989–2008

An approach to measure distance between compositional diet estimates containing essential zeros

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