Bromaghin, Jeffrey jbromaghin at usgs.gov
Mon Oct 5 11:19:20 PDT 2015

Dear colleagues,

I am pleased to announce the publication of an objective method to
establish bootstrap sample sizes for investigating the performance of
quantitative fatty acid signature analysis (QFASA), a method that has been
widely utilized for marine species.


Bromaghin, J. F. 2015. Simulating realistic predator signatures in
quantitative fatty acid signature analysis.  Ecological Informatics


Diet estimation is an important field within quantitative ecology,
providing critical insights into many aspects of ecology and community
dynamics. Quantitative fatty acid signature analysis (QFASA) is a prominent
method of diet estimation, particularly for marine mammal and bird species.
Investigators using QFASA commonly use computer simulation to evaluate
statistical characteristics of diet estimators for the populations they
study. Similar computer simulations have been used to explore and compare
the performance of different variations of the original QFASA diet
estimator. In both cases, computer simulations involve bootstrap sampling
prey signature data to construct pseudo-predator signatures with known
properties. However, bootstrap sample sizes have been selected arbitrarily
and pseudo-predator signatures therefore may not have realistic properties.
I develop an algorithm to objectively establish bootstrap sample sizes that
generates pseudo-predator signatures with realistic properties, thereby
enhancing the utility of computer simulation for assessing QFASA estimator
performance. The algorithm also appears to be computationally efficient,
resulting in bootstrap sample sizes that are smaller than those commonly
used. I illustrate the algorithm with an example using data from Chukchi
Sea polar bears (Ursus maritimus) and their marine mammal prey. The
concepts underlying the approach may have value in other areas

of quantitative ecology in which bootstrap samples are post-processed prior
to their use.

The paper is available at the following URL:



Jeffrey F. Bromaghin, PhD
Research Statistician
USGS Alaska Science Center
​Marine Ecosystems Office
4210 University Drive
Anchorage, AK 99508
jbromaghin at usgs.gov
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