Lake Ontario salmon (Salmo salar) were not migratory: A long-standing historical debate solved through stable isotope analysis

Isotopic life-history signatures are retained in modern and ancient Atlantic bluefin tuna vertebrae

Isotopic, tagging and diet studies of modern-day teleosts lack the ability to contextualise life-histories and trophic dynamics with a historical perspective, when exploitation rates were lower and climatic conditions differed. Isotopic analysis of vertebrae, the most plentiful hard-part in archaeological and museum collections, can potentially fill this data-gap. Chemical signatures of habitat and diet use during growth are retained by vertebrae during bone formation. However, to fulfil their potential to reveal life-history and trophic dynamics, we need a better understanding of the time-frame recorded by vertebrae, currently lacking due to a poor understanding of fish bone remodelling. To address this issue, we serially-sectioned four vertebral centra of the highly migratory Atlantic bluefin tuna (Thunnus thynnus; BFT) captured off Sardinia (Italy) and analysed their isotopic composition. We show how carbon (δ¹³ C), nitrogen (δ¹⁵ N) and sulfur (δ³⁴ S) isotope values can vary significantly across BFT vertebrae growth-axes, revealing patterning in dietary life-histories. Further, we find similar patterns are revealed through incremental isotopic analysis of inner and outer vertebrae centra samples from thirteen archaeological BFT vertebrae dating between the 9^th -13^th century CE. Our results indicate that multi-year foraging signatures are retained in vertebrae and allow for the study of life-histories in both modern and paleo-environments. These novel methods can be extended across teleost taxa owing to their potential to inform management and conservation on how teleost trophic dynamics change over time and what their long-term environmental, ecological, and anthropological drivers are.

Freshwater wetland–driven variation in sulfur isotope compositions: Implications for human paleodiet and ecological research

Sulfur isotope (δ34S) analyses are an important archaeological and ecological tool for understanding human and animal migration and diet, but δ34S can be difficult to interpret, particularly in archaeological human-mobility studies, when measured isotope compositions are strongly 34S-depleted relative to regional baselines. Sulfides, which accumulate under anoxic conditions and have distinctively low δ34S, are potentially key for understanding this but are often overlooked in studies of vertebrate δ34S. We analyze an ecologically wide range of archaeological taxa to build an interpretive framework for understanding the impact of sulfide-influenced δ34S on vertebrate consumers. Results provide the first demonstration that δ34S of higher-level consumers can be heavily impacted by freshwater wetland resource use. This source of δ34S variation is significant because it is linked to a globally distributed habitat and occurs at the bottom of the δ34S spectrum, which, for archaeologists, is primarily used for assessing human mobility. Our findings have significant implications for rethinking traditional interpretive frameworks of human mobility and diet, and for exploring the historical ecology of past freshwater wetland ecosystems. Given the tremendous importance of wetlands’ ecosystem services today, such insights on the structure and human dynamics of past wetlands could be valuable for guiding restoration work.

A millennium of trophic stability in Atlantic cod (Gadus morhua): transition to a lower and converging trophic niche in modern times

Stable isotope analyses of zooarchaeological material can be used to examine ecological variability in exploited species at centennial to millennial scales. Climate change is a notable driver of marine ecosystem change, although historical fishing is also likely to have impacted past marine systems. Fishing removes the oldest and largest individuals and may thereby result in shorter trophic pathways and reduced niche width of predatory fish species. In the current study we examine the trophic niche of Atlantic cod, haddock and Atlantic wolffish, in the last millennium using δ13C and δ15N values of bone collagen. We report a lower trophic level of Atlantic cod and haddock but higher level of wolffish in present times, following centuries at consistent and higher trophic levels of Atlantic cod. This results in a concurrent converging trophic niche of the demersal fish. We suggest that the current data set provides a valuable historical baseline facilitating interpretation of current variability in the trophic ecology of northern demersal fish.

Mobilizing the past to shape a better Anthropocene

As our planet emerges into a new epoch in which humans dominate the Earth system, it is imperative that societies initiate a new phase of responsible environmental stewardship. Here we argue that information from the past has a valuable role to play in enhancing the sustainability and resilience of our societies. We highlight the ways that past data can be mobilized for a variety of efforts, from supporting conservation to increasing agricultural sustainability and food security. At a practical level, solutions from the past often do not require fossil fuels, can be locally run and managed, and have been tested over the long term. Past failures reveal non-viable solutions and expose vulnerabilities. To more effectively leverage increasing knowledge about the past, we advocate greater cross-disciplinary collaboration, systematic engagement with stakeholders and policymakers, and approaches that bring together the best of the past with the cutting-edge technologies and solutions of tomorrow.

Ancient dog diets on the Pacific Northwest Coast: zooarchaeological and stable isotope modelling evidence from Tseshaht territory and beyond

Domestic dogs are frequently encountered in Indigenous archaeological sites on the Northwest Coast of North America. Although dogs depended on human communities for care and provisioning, archaeologists lack information about the specific foods dogs consumed. Previous research has used stable isotope analysis of dog diets for insight into human subsistence ('canine surrogacy' model) and identified considerable use of marine resources. Here, we use zooarchaeological data to develop and apply a Bayesian mixing model (MixSIAR) to estimate dietary composition from 14 domestic dogs and 13 potential prey taxa from four archaeological sites (2,900-300 BP) in Tseshaht First Nation territory on western Vancouver Island, British Columbia, Canada. Two candidate models that best match zooarchaeological data indicate dogs predominantly consumed salmon and forage fish (35-65%), followed by nearshore fish (4-40%), and marine mammals (2-30%). We compared these isotopic data to dogs across the Northwest Coast, which indicated a pronounced marine diet for Tseshaht dogs and, presumably, their human providers. These results are broadly consistent with the canine surrogacy model as well as help illuminate human participation in pre-industrial marine food webs and the long-term role of fisheries in Indigenous economies and lifeways.

From Land to Water: Taking Fish Welfare Seriously

This article aims to use contemporary (terrestrial) animal welfare science as a lens to evaluate the state of knowledge concerning welfare in fish species, focusing on farmed fishes. We take advantage of the vast expertise-including previous pitfalls and accomplishments-in the investigation of welfare in terrestrial vertebrates, borrowing questions and methodologies from terrestrial animal welfare science in order to (1) better understand the challenges and opportunities in the study of welfare in fish species, and (2) propose strategies for filling knowledge gaps.

Integrating fish scale and bone isotopic compositions for 'deep time' retrospective studies

Isotopic studies of archived fish scales have tremendous potential to develop long-term retrospectives that provide important insights into how humans have altered aquatic ecosystems. However, fish specimens in museum archives and other repositories typically date to time periods when the impacts of industrial societies may have already caused profound environmental changes. Archaeological fish bones offer an opportunity to bridge this key temporal gap by providing samples spanning from the recent past to as far back as the Pleistocene. Collagen is the primary protein component of both fish scale and bone, but the comparability of isotopic compositions from these tissues has not been established experimentally. To lay the framework for integrating isotopic datasets from these tissues, we compare δ¹³C and δ¹⁵N of bone and scale collagen, as well as other tissues, from fish with life-time controlled diets. Results show that while there is no difference in δ¹³C between scale and bone collagen, there may be a very slight but meaningful inter-tissue offset in δ¹⁵N (<0.3‰). We discuss potential sources of δ¹⁵N variation in scale and bone collagen measurements. Because there is no difference in scale and bone δ¹³C, and the observed offset in δ¹⁵N is very small (less than analytical uncertainty in many studies), our findings demonstrate that collagen isotopic compositions from these tissues should be directly comparable when integrating datasets from modern and ancient samples to build more powerful, millennium-scale isotopic times series. In linking isotopic compositions of collagen from modern, historical (scales), and archaeological (bones) fish, our findings open the way for more nuanced contextualization of how ecosystems functioned prior to large-scale exploitation and how they have responded to mounting anthropogenic pressures in the intervening centuries.

Differentiating salmonid migratory ecotypes through stable isotope analysis of collagen: Archaeological and ecological applications

The ability to distinguish between different migratory behaviours (e.g., anadromy and potamodromy) in fish can provide important insights into the ecology, evolution, and conservation of many aquatic species. We present a simple stable carbon isotope (δ13C) approach for distinguishing between sockeye (anadromous ocean migrants) and kokanee (potamodromous freshwater residents), two migratory ecotypes of Oncorhynchus nerka (Salmonidae) that is applicable throughout most of their range across coastal regions of the North Pacific Ocean. Analyses of kokanee (n = 239) and sockeye (n = 417) from 87 sites spanning the North Pacific (Russia to California) show that anadromous and potamodromous ecotypes are broadly distinguishable on the basis of the δ13C values of their scale and bone collagen. We present three case studies demonstrating how this approach can address questions in archaeology, archival, and conservation research. Relative to conventional methods for determining migratory status, which typically apply chemical analyses to otoliths or involve genetic analyses of tissues, the δ13C approach outlined here has the benefit of being non-lethal (when applied to scales), cost-effective, widely available commercially, and should be much more broadly accessible for addressing archaeological questions since the recovery of otoliths at archaeological sites is rare.

Maintaining Traditions: Food and Identity among Early Immigrants to Upper Canada

A critical examination of the relationships between food and identity is explored among early British and American Loyalist settlers in Upper Canada (southern Ontario) from the late 18th to the late 19th centuries. This research synthesizes zooarchaeological data from the region and interprets these alongside historical texts to address how meat was incorporated into early immigrant diets. Previous scholarship generally agreed that pork played a dominant role in Upper Canadian cuisine and that residents first settling in the area were particularly reliant on wild meat resources. Archaeological evidence suggests this was not the case. Results and discussions highlight the influence of British working-class traditions on Upper Canadian identities and the development of regional cuisines in southern Ontario. Parallels are drawn to anthropological and sociological studies of migrant foodways, encouraging archaeologists to consider the importance of maintaining food traditions when examining early immigrant assemblages.

Fish and maize: Bayesian mixing models of fourteenth- through seventeenth-century AD ancestral Wendat diets, Ontario, Canada

Freshwater and marine fish have been important components of human diets for millennia. The Great Lakes of North America, their tributaries and smaller regional freshwater bodies are important Native American fisheries. The ethnohistorical record, zooarchaeological remains, and isotopic values on human bone and tooth collagen indicate the importance of fish in fourteenth- through seventeenth-century ancestral Wendat diets in southern Ontario, which is bordered by three of the Great Lakes. Maize (Zea mays ssp. mays) was the primary grain of Native American agricultural systems in the centuries prior to and following sustained European presence. Here we report new Bayesian dietary mixing models using previously published δ¹³C and δ¹⁵N values on ancestral Wendat bone and tooth collagen and tooth enamel. The results confirm previous estimates from δ¹³C values that ancestral Wendat diets included high proportions of maize but indicate much higher proportions of fish than has previously been recognized. The results also suggest that terrestrial animals contributed less to ancestral Wendat diets than is typically interpreted based on zooarchaeological records.

Freshwater reservoir offsets on radiocarbon-dated dog bone from the headwaters of the St. Lawrence River, USA

Isotopic analysis of dog (Canis lupus familiaris) bone recovered from archaeological sites as proxies for human bone is becoming common in North America. Chronological placement of the dogs is often determined through radiocarbon dating of dog bone. The Great Lakes, their tributaries, and nearby lakes and streams were important fisheries for Native Americans prior to and after sustained European presence in the region. Carbon entering the food web in freshwater systems is often not in full isotopic equilibrium with the atmosphere, giving rise to spuriously old radiocarbon ages in fish, other aquatic organisms, and their consumers. These freshwater reservoir offsets (FROs) have been noted on human and dog bone in several areas of the world. Here we report the results of multi-tracer Bayesian dietary modeling using δ¹⁵N and δ¹³C values on dog bone collagen from mid-fifteenth to mid-sixteenth-century Iroquoian village sites at the headwaters of the St. Lawrence River, New York, USA. Results indicate that fish was an important component of dog diets. A comparison of radiocarbon dates on dog bone with dates on deer bone or maize from the same sites indicate FROs ranging from 97 ± 24 to 220 ± 39 ¹⁴Cyr with a weighted mean of 132 ± 8 ¹⁴Cyr. These results suggest that dog bone should not be used for radiocarbon dating in the absence of modeling to determine fish consumption and that previously reported radiocarbon dates on human bone from the larger region are likely to have FROs given the known importance of fish in regional human diets.

Long-term ecological changes in marine mammals driven by recent warming in northwestern Alaska

Carbon and nitrogen isotopes analyses were performed on marine mammal bone collagen from three archaeological sites (ad 1170-1813) on Cape Espenberg (Kotzebue Sound, northwestern Alaska) as well as modern animals harvested from the same area to examine long-term trends in foraging ecology and sea ice productivity. We observed significant and dramatic changes in ringed seal stable isotope values between the early 19th and early 21st centuries, likely due to changing sea ice productivity and reduced delivery of organic matter to the benthos driven by recent warming in the Arctic. These data highlight the importance of the archaeological record for providing a long-term perspective on environmental variation and interpreting recent changes driven by anthropogenic processes.