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Stable isotope signal homogeneity and differences between and within pinniped muscle and skin
Author(s) -
Todd Sean K.,
Holm Bethany,
Rosen David A. S.,
Tollit Dominic J.
Publication year - 2010
Publication title -
marine mammal science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.723
H-Index - 78
eISSN - 1748-7692
pISSN - 0824-0469
DOI - 10.1111/j.1748-7692.2009.00345.x
Subject(s) - marine mammal , marine research , archaeology , columbia university , mammal , geography , fishery , ecology , oceanography , media studies , biology , geology , sociology
Stable isotope analysis (SIA) is often used to examine diet choice and trophic relationships in marine mammals (e.g., see Hobson 1999, Kelly 2000). However, the technique makes a number of largely untested assumptions (Gannes et al. 1997). For example, because marine mammal SIA studies typically sample only a small section of tissue (due to logistical or animal welfare considerations), researchers often assume that biopsy to be representative of the whole animal—that is, that the isotopic signal is homogenous within a tissue. Further, there is little standardization among (or within) studies regarding appropriate tissue sampling protocols, which may lead to bias if isotope ratios are sufficiently heterogeneous within tissues. This problem may be greater when biopsies are obtained through remote darting, a nonlethal method of obtaining samples for a variety of marine mammals (Gemmel and Majluf 1997, Todd et al. 1997, Kurle and Worthy 2002, Herman et al. 2005) as such methods severely limit the ability to accurately select specific target areas. Isotopic composition may differ across the body within the same tissue type due to differential assimilation or catabolization rates. In addition, while a variety of tissue types can be used to determine stable isotope values, differences in stable isotope value between tissues are not always known.