Measuring the potential influence of cooking on the carbon and nitrogen isotopic composition of spawning Chinook salmon Briana Doering 1 abstract article info Article history: Received 14 November 2016 Received in revised form 23 February 2017 Accepted 24 February 2017 Available online xxxx This study considers the effect of heat treatment (cooking) on muscle tissue from modern spawning Alaskan Chi- nook salmon (Oncorhynchus tshawytscha) and implications for archaeological dietary reconstructions. Here, it is demonstrated that cooking, potentially through exposure to lighter volatiles present in wood smoke, significantly alters the stable carbon (δ 13 C) isotopic composition of muscle tissue, though the difference may be too slight (-0.50‰) to be incorporated into dietary mixing models. Cooking produces no significant change in nitrogen (δ 15 N) values. Additionally, this study identifies significant differences in stable nitrogen (δ 15 N) and carbon (δ 13 C) isotopic values between previous studies on coastal adult Chinook salmon and the spawning adult Chi- nook salmon from Central Alaska analyzed in this study, emphasizing the importance of employing isotopic data from local fauna in dietary reconstructions. The data presented here have implications not only for our un- derstanding of general salmon ecology, but also for refining archaeological reconstructions of prehistoric diet in Central Alaska and other regions where smoke-preserved tissue was regularly consumed. © 2017 Elsevier Ltd. All rights reserved. Keywords: Isotopic analysis Cooking Central Alaska Salmon 1. Introduction Alaskan archaeologists have relied largely on a direct analysis of fau- nal remains to reconstruct prehistoric diet and track dietary changes through time (Goebel, 2011; Hoffecker, 2005; Holmes, 2001; Dixon, 1999). However, there are several limitations on our ability to recon- struct the importance of different dietary items in prehistory using physical remains alone, and this is particularly true for smaller game like fish. The small bones of fish do not preserve well in Central Alaska's acidic soils and tend to pass readily through the standard screen sizes routinely used in excavation (Ping et al., 2005; Thomas, 1969). Preserva- tion conditions are further worsened by high winds and sparse vegeta- tion, which have resulted in very shallow soil deposits across much of the region (Yesner, 1996). Additionally, unlike the stone tools employed in hunting large game, the nets, traps, and smoking racks used to capture and process fish are typically constructed from organic materials that infrequently survive the conditions described above (Fienup-Riordan, 1986; Schiffer, 1983; McKennan, 1981). Owing in part to these taphonomic and site formational factors, studies of prehistoric subsistence practices in Alaska have primarily focused on the importance of large mammals, such as caribou, bison, wapiti, and moose (Potter, 2016; Graf and Bigelow, 2011; Esdale, 2008; Dixon, 1999), rather than aquatic resources like fish, though they are known to be critical to Central Alaskan subsistence today (Loring and Gerlach, 2010). Food preservation techniques have also been under-discussed in ar- chaeological reconstructions of Central Alaskan subsistence practices, despite a wealth of ethnographic evidence pointing to the importance of smoked or fermented meats as a winter food for contemporary Alaskans (Fienup-Riordan, 1986; Nelson, 1986). Today, salmon are fre- quently hot or cold smoked for several days (Buklis, 1999; Ames, 1994; Fienup-Riordan, 1986), driving off moisture and transforming the raw food product into one that is lighter and can be stored for long periods without risk of spoiling (Horner, 1997). This relatively sim- ple technique can greatly enhance the transportability and longevity of the original raw food product. If cooking—whether through exposure to smoke or heat—has a sig- nificant and measurable isotope effect, it may be possible to establish proxies for identifying different cooking techniques. While previous ex- perimental isotopic studies have considered the potential isotopic ef- fects of cooking on fish bones, they have not considered how it may affect the isotopic composition of muscle tissue (Fernandes et al., 2014). Identifying an isotopic proxy for preservation techniques such as smoking would allow archaeologists to better reconstruct critical pre- historic survival strategies and understand the role of long-term climate change in the development of these now-common preservation tech- niques. An isotopic proxy for such techniques could be used to measure differences in human remains or soil to identify when such a transition occurred. Recent discoveries of the earliest evidence for salmon fishing in Central Alaska at the archaeological site of Upward Sun River have Journal of Archaeological Science: Reports 12 (2017) 491–498 E-mail address: doeringb@umich.edu. 1 Permanent address: Ruthven Museums Building, Rm 4013, 1109 Geddes Ave, Ann Arbor, MI 48109. http://dx.doi.org/10.1016/j.jasrep.2017.02.028 2352-409X/© 2017 Elsevier Ltd. All rights reserved. Contents lists available at ScienceDirect Journal of Archaeological Science: Reports journal homepage: www.elsevier.com/locate/jasrep