Malte Willmes

• PhD
• Researcher at Norwegian Institute for Nature Research

Strontium isotope ratios measured in fossil human teeth are a powerful tool to investigate past mobility patterns. In order to apply this method, the sample needs to be investigated for possible diagenetic alteration and a least destructive analytical technique needs to be employed for the isotopic analysis. We tested the useability of U, Th, and Z...

Strontium isotope ratios (⁸⁷Sr/⁸⁶Sr) of archaeological samples (teeth and bones) can be used to track mobility and migration across geologically distinct landscapes. However, traditional interpolation algorithms and classification approaches used to generate Sr isoscapes are often limited in predicting multiscale ⁸⁷Sr/⁸⁶Sr patterning. Here we inves...

Fall-run Chinook salmon (Oncorhynchus tshawytscha) from the Sacramento–San Joaquin River system form the backbone of California’s salmon fishery and are heavily subsidized through hatchery production. Identifying temporal trends in the relative contribution of hatchery- versus wild-spawned salmon is vital for assessing the status and resiliency of...

Effective conservation of endangered species requires knowledge of the full range of life-history strategies used to maximize population resilience within a stochastic and ever-changing environment. California’s endemic Delta Smelt (Hypomesus transpacificus) is rapidly approaching extinction in the San Francisco Estuary, placing it in the crossfire...

Measuring the growth of migratory fish across habitats is difficult because field observations only provide a snapshot into their life; yet, understanding which habitats provide better growth opportunities is crucial for their conservation. We experimentally enclosed individually tagged juvenile Chinook Salmon (Oncorhynchus tshawytscha) in habitats...

As fish populations face compounding pressures under climate change, highly modified rivers are receiving increasing research and conservation attention as important sites for restoration. Across the North Pacific Ocean, Chinook salmon (Oncorhynchus tshawytscha) have experienced unprecedented declines and extirpations because of habitat loss and fr...

Intraspecific biodiversity is vital for species persistence in an increasingly volatile world. By embracing methods that integrate information at different spatiotemporal scales, we can directly monitor and reconstruct changes in intraspecific biodiversity. Here we combined genetics and otolith biochronologies to describe the genotypic and phenotyp...

Chinook salmon (Oncorhynchus tshawytscha) display remarkable life history diversity, underpinning their ability to adapt to environmental change. Maintaining life history diversity is vital to the resilience and stability of Chinook salmon metapopulations, particularly under changing climates. However, the conditions that promote life history diver...

Phenotypic diversity and abundance drive salmon resilience in the face of increasing environmental variability. But what happens when human activities fundamentally alter the habitat complexity that drives this diversity? And how can we restore habitats to recover both diversity and abundance to support salmon persistence in a warming climate? Here...

Objective The illegal introduction of fish species can disrupt ecosystems, collapse food webs, and undermine recreational fishing opportunities. Determining whether introduced fish are locally reproducing is important for resource managers. Here, we used the geochemical analysis of otoliths to investigate the potential illegal introduction of a Wal...

Salmonids are well known for their natal homing behaviour, meaning they return to breed in the same area where they originated. However, not all individuals return to their natal breeding grounds—a behavioural trait known as straying. The prevalence of straying is difficult to explore and therefore quantitative estimates for straying are seldom rep...

Largemouth bass Micropterus salmoides, a popular warm water sport fish, is routinely stocked in reservoirs throughout the USA to augment wild populations. Evaluating if these supplementations are successful requires distinguishing hatchery-sourced fish from their wild counterparts. From 2011 to 2019, over 467 000 largemouth bass fingerlings were st...

Zooarchaeological analysis is a useful means of exploring faunal palaeoecology, paleoclimate and past human behaviours. The Middle Pleistocene archaeological site Lazaret Cave, located in modern-day Nice, France, features a vast assemblage of faunal remains pertinent to the understanding of early Neanderthal subsistence behaviours as well as red de...

In a system that uses supplemental stocking to enhance a fishery that serves a dual purpose, an understanding of the contributions from natural and hatchery-produced fish is important so that hatchery resources can be appropriately allocated. Kokanee Oncorhynchus nerka were first stocked in Flaming Gorge Reservoir (FGR), Wyoming-Utah, in 1963 and s...

Developmental abnormalities in otoliths can impact growth and survival in teleost fishes. Here, we quantified the frequency and severity of developmental anomalies in otoliths of delta smelt (Hypomesus transpacificus), a critically endangered estuarine fish that is endemic to the San Francisco Estuary. Left–right asymmetry and anomalous crystalline...

Understanding the relative contributions of different spawning habitats to adult fish populations is central to effective fisheries management and species conservation. The Tarek (Alburnus tarichi) is an adfluvial cyprinid that is endemic to the alkaline-saline waters of Lake Van, Turkey. Tarek are culturally and economically important to the regio...

Graphical abstract for our recent publication on the use of otoliths in fisheries science.

Chemical analysis of calcified structures continues to flourish, as analytical and technological advances enable researchers to tap into trace elements and isotopes taken up in otoliths and other archival tissues at ever greater resolution. Increasingly, these tracers are applied to refine age estimation and interpretation, and to chronicle respons...

Strontium isotopes (87 Sr/ 86 Sr) provide valuable information to help reconstruct past mobility. For the analysis of archaeological tooth enamel to provide a direct assessment of mobility, a comparison to the baseline 87 Sr/ 86 Sr in a region is required. In this study, a large-scale 87 Sr/ 86 Sr baseline of Portugal is created based on 151 paired...

Migration is a complex phenotypic trait with some species containing migratory and non-migratory individuals. Such life history variation may be attributed in part to plasticity, epigenetics, or genetics. Although considered semi-anadromous, recent studies using otolith geochemistry have revealed life history variation within the critically endange...

Understanding life-history diversity in a population is imperative to developing effective fisheries management and conservation practices, particularly in degraded environments with high environmental variability. Here, we examined variation in habitat use and migration patterns of White Sturgeon (Acipenser transmontanus), a long-lived migratory f...

Your dentist can tell a lot about your health and daily habits just by looking at your teeth. But did you know that archaeological scientists have discovered that there is a lot more information hidden in teeth? We can study the chemical composition of teeth and can find out what types of food a person ate, and even where that food was growing. Whe...

Food availability is a key determinant of the nursery value of a given habitat for larval and juvenile fishes. Growth, survival, and recruitment success are often inter-correlated and influenced by prey availability and associated feeding success. This is likely true for the threatened population of Longfin Smelt ( Spirinchus thaleichthys ) in the...

Strontium isotope ratios (87Sr / 86Sr) are a key geochemical tracer used in a wide range of fields including archaeology, ecology, food and forensic sciences. These applications are based on the principle that the Sr isotopic ratios of natural materials reflect the sources of strontium available during their formation. A major constraint for curren...

Seven adult human teeth from Cave T1 were analysed for trace element concentrations using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS) and strontium isotope compositions using Laser Ablation Multi-Collector Inductively Coupled Plasma Mass Spectrometry (LA-MC-ICPMS). The aim of this study was to examine whether the people b...

Strontium isotope ratios (87Sr = 86Sr) of biogenic material such as bones and teeth reflect the local sources of strontium ingested as food and drink during their formation. This has led to the use of strontium isotope ratios as a geochemical tracer in a wide range of fields including archaeology, ecology, food studies and forensic sciences. In ord...

Strontium isotope ratios (87Sr/86Sr) of archaeological samples (teeth and bones) can be used to track mobility and migration across geologically distinct landscapes. However, traditional interpolation algorithms and classification approaches used to generate Sr isoscapes are often limited in predicting multiscale 87Sr/86Sr patterning. Here we inves...

The burial mound of Le Tumulus des Sables, southwest France, contains archaeological artefacts spanning from the Neolithic to the Iron Age. Human remains have been found throughout the burial mound, however their highly fragmented state complicates the association between the burial mound structure and the archaeological material. Radiocarbon datin...

Background The application of otolith-based tools to inform the management and conservation of fishes first requires taxon- and stage-specific validation. The Delta Smelt ( Hypomesus transpacificus ), a critically endangered estuarine fish that is endemic to the upper San Francisco Estuary (SFE), California, United States, serves as a key indicator...

Floodplains represent critical nursery habitats for a variety of fish species due to their highly productive food webs, yet few tools exist to quantify the extent to which these habitats contribute to ecosystem-level production. Here we conducted a large-scale field experiment to characterize differences in food web composition and stable isotopes...

In estuaries, fluctuating environmental conditions exact strenuous physiological demands on the fishes that inhabit these oft-impacted areas, including the Critically Endangered delta smelt Hypomesus transpacificus in California (USA). Using an archive of otoliths spanning 2011-2019, we examined how growth rates of wild subadult delta smelt vary on...

Estuaries are places where fresh water from rivers mixes with salty water from the ocean. Why does this matter? This mixing creates dynamic, ever-changing conditions that fishes must navigate in order to survive. Environmental conditions can change yearly, seasonally, daily, and even hourly. Fishes use many different strategies to adjust to this wi...

Conodont microfossils record seawater strontium isotope values (⁸⁷Sr/⁸⁶Sr), permitting chemostratigraphic correlation for tectonic and climatic reconstructions of the Paleozoic and early Mesozoic (541–201 Ma). Laser ablation multiple collection inductively coupled plasma mass spectrometry (LA MC-ICP-MS) can provide rapid, high spatial resolution ⁸⁷...

Strontium isotope ratios (87Sr / 86Sr) of biogenic material such as bones and teeth reflect the local sources of strontium ingested as food and drink during their formation. This has led to the use of strontium isotope ratios as a geochemical tracer in a wide range of fields including archaeology, ecology, food studies and forensic sciences. In ord...

Establishing strontium isotope (87 Sr/ 86 Sr) geographical variability is a key component of any study that seeks to utilize strontium isotopes as tracers of provenance or mobility. Although lithological maps can provide a guideline, estimations of bioavailable 87 Sr/ 86 Sr are often necessary, both in qualitative estimates of local strontium isoto...

White Sturgeon (Acipenser transmontanus) are a long-lived, slow-growing, and late-reproducing anadromous fish common in estuaries and coastal habitats along the North American West Coast. These life history characteristics make populations vulnerable to human impacts and a challenge to study and manage. Previous studies in the San Francisco Estuary...

Chinook salmon (Oncorhynchus tshawytscha) populations in California are in decline due to the combined effects of habitat degradation, water diversions, and shifting climate regimes. Effective salmon conservation and management relies on understanding their life history diversity and ability to adapt to environmental change. Monitoring efforts and...

Delta Smelt (Hypomesus transpacificus) is an endangered, endemic fish species that functions as an indicator species of ecosystem health in the SFE. Over time, conservation efforts have been based on a semi-anadromous life history model. However, surprising otolith chemistry analyses suggested some individuals do not disperse into brackish water du...

Introduction: Global and regional climate models predict warming temperatures over the next century. Laboratory studies indicate that timing of Delta Smelt spawning/hatching is related to temperature. As a result, climate change may shift hatch dates by ~5 days/decade or up to 50 days by 2100. We examined how the correlation between hatch dates and...

Chinook Salmon (Oncorhynchus tshawytscha) populations in California are in decline due to the combined effects of habitat degradation, water diversions, and climate change. Reduced life‐history diversity within these populations inhibits their ability to respond to these stressors. Putah Creek, a small creek in California’s Central Valley that once...

Strontium isotope ratios (87Sr/86Sr) of biogenic carbonates such as bones and teeth reflect the local sources of strontium ingested as food and drink during their formation. This has led to the use of strontium isotope ratios as a geochemical tracer in a wide range of fields including archaeology, ecology, food studies and forensic sciences. In ord...

Our study describes newly discovered spawning and rearing habitats of Longfin Smelt (Spirinchus thaleichthys) in brackish tidal wetlands near Silicon Valley, California. The Longfin Smelt is a threatened estuarine forage fish native to the San Francisco Estuary. Prior to our observations, it was not known that Longfin Smelt utilized and spawned in...

A comprehensive understanding of the life history strategies and habitat use of species is essential for developing accurate ecological models and effective management and conservation strategies. For example, omitting critical habitats of endangered species when estimating their abundance and when designing conservation plans for them can severely...

Results of surveys for adult and larval Longfin Smelt in wetlands throughout the San Francisco Estuary. Includes special studies of otolith growth and chemistry, and genetic identifications.

Rationale Oxygen isotope ratios (δ¹⁸O values) of fish otoliths (ear bones) are valuable geochemical tracers of water conditions and thermal life history. Delta Smelt (Hypomesus transpacificus) are osmerid forage fish endemic to the San Francisco Estuary, California, USA and are on the verge of extinction. These fish exhibit a complex life history t...

Neanderthals had complex land use patterns, adapting to diversified landscapes and climates. Over the past decade, considerable progress has been made in reconstructing the chronology, land use and subsistence patterns, and occupation types of sites in the Rhône Valley, southeast France. In this study, Neanderthal mobility at the site of Payre is i...

Table A. Types of flint used at Abri des Pêcheurs in the Middle Palaeolithic sequence (MIS 4), after [84]. Table B. Types of flint and products in the Middle Palaeolithic sequence at Abri des Pêcheurs. (DOCX)

It has been estimated that up to 25% of Indigenous human remains held in Australian institutions are unprovenanced. Geochemical tracers like strontium isotope ratios (87Sr/86Sr) have been used globally for over 40 years to discern human provenance and provide independent data to aid in repatriation efforts. To reliably apply this technology, landsc...

The IsoFishR application is a data reduction and analysis tool for laser-ablation strontium isotope data, following common best practices and providing reliable and reproducible results. Strontium isotope ratios (87 Sr/ 86 Sr) are a powerful geochemical tracer commonly applied in a wide range of scientific fields and laser-ablation inductively coup...

The IsoFishR application is a data reduction and analysis tool for laser-ablation strontium isotope data, following common best practices and providing reliable and reproducible results. Strontium isotope ratios (⁸⁷Sr/⁸⁶Sr) are a powerful geochemical tracer commonly applied in a wide range of scientific fields and laser-ablation inductively coupled...

Strontium isotope ratios (⁸⁷Sr/⁸⁶Sr) are gaining considerable interest as a geolocation tool and are now widely applied in archaeology, ecology, and forensic research. However, their application for provenance requires the development of baseline models predicting surficial ⁸⁷Sr/⁸⁶Sr variations (“isoscapes”). A variety of empirically-based and proc...

Strontium isotope ratios (87 Sr/ 86 Sr) are gaining considerable interest as a geolocation tool and are now widely applied in archaeology, ecology, and forensic research. However, their application for provenance requires the development of baseline models predicting surficial 87 Sr/ 86 Sr variations ("isoscapes"). A variety of empirically-based an...

The objective of this study was to validate the use of fin ray strontium isotope ratios (⁸⁷Sr:⁸⁶Sr) via laser ablation to resolve fine-scale movement patterns in sturgeons (Acipenseridae) during freshwater rearing in early life stages. We conducted a laboratory experiment using juvenile White Sturgeon Acipenser transmontanus, in which we exposed ju...

Article in press doi: 10.1002/oa.2578 Mesolithic human remains are rare in the archaeological record of the French Mediterranean. Only the island of Corsica has so far produced relatively well preserved burials, and recent archaeological excavations have brought to light new Mesolithic human remains. The site of Campu Stefanu, located in Sollacaro...

Mesolithic human remains are rare in the archaeological record of the French Mediterranean. Only the island of Corsica has so far produced relatively well-preserved burials, and recent archaeological excavations have brought to light new Mesolithic human remains. The site of Campu Stefanu, located in Sollacaro in the southeast of the island, contai...

Strontium isotope ratios (⁸⁷Sr/⁸⁶Sr) in otoliths are a well-established tool to determine origins and movement patterns of fish. However, otolith extraction requires sacrificing fish, and when working with protected or endangered species, the use of nonlethal samples such as scales, spines, and fin rays is preferred. Unlike otoliths that are predom...

Human mobility in recent history is well documented and often related to drastic external changes, including war, famine, and the discovery and exploration of new geographic regions and resources. Reconstruction of mobility patterns in prehistory is thus a crucial part of understanding the forces that drove our ancestors, but it is complicated by t...

The Ries crater is a well-preserved, complex impact crater that has been extensively used in the study of impact crater formation processes across the solar system. However, its geologic structure, especially the megablock zone, still poses questions regarding crater formation mechanics. The megablock zone, located between the inner crystalline rin...

Strontium isotope ratios (87Sr/86Sr) are a key geochemical tracer used in a wide range of fields including archaeology, ecology, food and forensic sciences. These applications are based on the principle that the Sr isotopic ratios of natural materials reflect the sources of strontium available during their formation. A major constraint for current...

Strontium isotope ratios (87Sr/86Sr) measured in ancient human remains can be used to reconstruct migration patterns of ancient human populations. This application is based on the fact that different geologic regions have distinct Sr isotope signatures that are cycled through the soils, plants and rivers, and eventually enter the food cycle. Sr iso...

Strontium isotope ratios (87Sr/86Sr) are used as a geochemical tracer in a wide range of fields including archaeology, ecology, soil, food and forensic sciences. These applications are based on the principle that strontium isotopic ratios of materials reflect the geological sources of the strontium, which were available during its formation. Geolog...

The dataset consists of 87Sr/86Sr isotope ratios of plant samples and soil leachates covering the major geologic regions of France. In addition to the isotope data it provides the spatial context for each sample, including background geology, field observations and soil descriptions. The dataset can be used to create Sr isoscapes for France, which...

The mid- and high-latitudes of Mars are covered by a smooth young mantle that is interpreted as an atmospherically derived air-fall deposit of ice and dust related to recent climate changes. In order to determine relative and absolute ages of this surface unit within the southern hemisphere, a systematic survey of all available HiRISE and CTX image...

Strontium isotope ratios (87Sr/86Sr) can be used for the reconstruction of human and animal migrations across geologically different terrains. Sr isotope ratios in rocks are a product of age and composition and thus vary between geologic units. From the eroding environment Sr is transported into the soils, plants and rivers of a region. Humans and...

New details are uncovered about the overturning and emplacement of impact ejecta at the classic impact site: Meteor Crater.

A comprehensive map of the megablock zone of the Ries crater in Germany was created by means of remote sensing and shallow drilling, and the distribution of the megablocks in relation to the crater center and crater rim was determined.

The Ries impact structure, located in Bavaria, southern Germany, has a diameter of 26 km. It is one of the best studied impact craters on the Earth and it is used as an archetype for complex craters across the solar system [e.g. 1, 2]. However its geologic structure still poses questions regarding crater formation mechanics and about the distributi...

The surface of Mars is partially covered by a latitude-dependent ice-rich smooth mantle in the middle and high latitudes (±30-60°) [1, 2]. These deposits relate to changes in the obliquity of Mars which have led to major shifts in the Martian climate and repeated global episodes of deposition [3]. The deposits vary in thickness and are usually inde...