Abstract
Stable isotope analysis (SIA) provides ecological data that can be safely and efficiently
collected on endangered, threatened, and cryptic species. Marine mammals are an ecologically important
group for which economical and logistical constraints can make data collection challenging. Stranded
marine mammals are often used in research, but the causes of strandings and subsequent tissue
decomposition could affect SIA. We conducted a three-part study to test the validity of using δ13 C and
δ15 N values from tissues of stranded bottlenose dolphins (Tursiops truncatus) and West Indian manatees
(Trichechus manatus) for ecological studies. First, we quantified isotopic overlap using ellipses based on
95% of the data to compare isotope values in skin between stranded and live-captured animals. Second,
we compared stable isotope values from liver, skin, and muscle from animals that had stranded and were
sampled at different decomposition stages. Third, we experimentally exposed each tissue to
environmental conditions and sampled tissues as they decomposed. For both dolphins and manatees,
isotopic ellipses from skin of stranded carcasses were similar to live-captured individuals. Among
individuals recovered at different decomposition stages, more advanced decomposition affected δ13 C
values in dolphin liver and skin but not in manatee tissues and had no effect on δ15 N values in any tissue
for either species. In the experimental manipulation, decomposition resulted in depleted δ13 C values,
enriched δ15 N values, and increased C:N in liver for both species. Skin and muscle from stranded dolphins
and manatees are representative of their corresponding live populations and can be used for SIA with
appropriate caution. To facilitate the use of tissues from stranded animals, tissues should be dried or
frozen for storage as soon as possible after sampling. We recommend liver from stranded animals only be
used for SIA when researchers need tissues with short turnover times and can access fresh samples.
Without consideration of decomposition effects on isotope values, ecologists may make inaccurate
inferences about habitat use, diet, and community structure. Careful use of SIA on tissues from stranded
animals can help researchers provide better quality information for managers and policymakers.
Purpose
This file contains two datasheets. The first sheet, titled read.me, contains column title
information for the second sheet. The second sheet, title Data, contains data on stable isotope values from
live and dead stranded dolphins and manatees as well as the tissue sampled (liver, skin, muscle), the
condition code specifying whether the sample was from a live or dead animal and, if dead, the
decomposition code at time of sampling. This sheet also contains information on the year of sampling, the
total amount of carbon and nitrogen in the sample. Samples from live dolphins were from Mobile Bay,
AL during 2019 and 2020. Samples from stranded animals were from 2011-2019 from coastal Alabama
waters. Samples from live manatees were taken from animals between 2009-2017. Samples from stranded
manatees were taken between 2008-2017. These data were used to test the first two objectives in the study
outlined above.
DOI: 10.57778/9xbe-kr37
Suggested Citation
Cloyed, C., Carmichael, R., Clance, L., & Bouveroux, T. (2022). Stable isotope values of live and stranded dolphins and manatees from the northern Gulf of Mexico [Data set]. Dauphin Island Sea Lab. https://doi.org/10.57778/9XBE-KR37
Related Publication Citation
Cloyed, C.S., Johnson, C., DaCosta, K.P., Clance, L.R., Russell, M.L., Díaz Clark, C., Hieb,
E.E., Carmichael, R.H. (2023). Effects of tissue decomposition on stable isotope ratios and implications
for use of stranded animals in research. Ecosphere
