Project highlights

  • Exploit the outstanding archaeological fish fossil record to characterize behavioural patterns over the past 2500 years for key fish species in the Gulf of Mexico.
  • Use cutting edge approaches to identify habitat and spawning mobility traits that are essential for developing better ecosystem-orientated conservation strategies to protect the world’s largest sheepshead (Archosargus probatocephalus) fishery
  • Opportunities to travel to collect data from fossil collections in New Orleans and elsewhere in the USA.


Understanding diet and spawning behaviour is critical for developing ecosystem-orientated conservation strategies for saving vulnerable fish species because it allows authorities to target key times and locations for protection, thus helping to balance the economic needs of fisheries with those of ecosystem health in order to achieve long-term, sustainable food security. However, because scientific observation of most aquatic ecosystems has only been established in recent decades, conservation decisions are often necessarily made without key details on how aquatic ecosystems respond to long-term changes in fisheries exploitation and environmental conditions. The physical and chemical characteristics of ancient fish bones and teeth reflect specific behaviours and ecosystem dynamics and can thus serve as a record for investigating long-term patterns in order to anticipate how future fish stocks can be sustainably managed.

While the fish known as ‘sheepshead’ have always been part of the Gulf of Mexico fisheries, they were often overlooked in favour of more profitable species. However, as more commercially desirable fish become more scarce, sheepshead populations are under increasing pressure – a scenario emblematic of the global crises of ‘fishing down food chains’.

Approaches refined by the project supervisors demonstrate that fish bone isotopic compositions (Guiry et al. 2016, 2020ab) as well as wear and surface damage on teeth (Purnell and Darras 2015) can provide robust markers for reconstructing feeding habitats and migratory patterns. This project will apply these techniques to sheepshead and other fish bones and teeth, which are abundant in the archaeological and historical archives spanning the last 2500 years (de France and Kennedy 2020), to reveal key behavioural characteristics for conservation management priorities (Vanderkooy 2006) including: (1) identifying sub populations in order to better protect spawning aggregations during critical times of the year, and (2) assessing the importance of increasingly vulnerable areas of aquatic vegetation (sea grass beds) in order to quantify the impact their loss would have on sheepshead life history stages.

More broadly, despite growing calls for a better understanding of past environments, to inform rehabilitation of degraded ecosystems, it is still uncommon for researchers of the past (archaeology) and present (ecology) to directly integrate perspectives between disciplinary ‘silos’ (Guiry and Hunt 2020). This is a key obstacle as archaeological evidence may offer the only source of data for addressing longer-term aspects of ecosystem change. In this context, this project will serve as an important model for future research.



University of Leicester


  • Climate and Environmental Sustainability
  • Organisms and Ecosystems


Project investigator

  •  Dr Eric Guiry, University of Leicester


  • Prof. Mark Purnell, University of Leicester
  • Dr Ryan Kennedy, University of New Orleans

How to apply


Dietary analysis will be based on two proxies: stable carbon, nitrogen, and sulfur isotope analyses of bone, scale, and tooth protein using approaches developed by Guiry (Guiry and Szpak 2020; Guiry and Hunt 2020, Guiry et al. 2016), and quantitative analysis of surface damage and wear using approaches developed by Purnell (Purnell and Darras 2015). Spawning and habitat use patterns will be linked directly with diet and ‘ground truthed’ using modern and historical specimens to build a framework for millennium-scale retrospectives on fish behaviour. The project will also explore new methods for taxonomic identification, based on zooarchaeological techniques. New approaches to taphonomic analysis of postmortem wear in fish elements (pre- and post-burial) will also be developed.

Training and skills

Project specific training will include: zooarchaeological fish identification; ancient, historical, and modern protein extraction; isotope ratio mass spectrometry; and multivariate dental microwear texture analyses. The emphasis will be on robust isotopic and quantitative analysis as well as statistical hypothesis testing.

Partners and collaboration

Dr Eric Guiry, Prof. Mark Purnell, and Dr Ryan Kennedy have long track records of innovative research in the archaeology, palaeobiology, and taphonomy of fish. Guiry has expertise in the use of fish isotopic compositions to reconstruct past dietary behaviour and ecosystem dynamics. Purnell has expertise in the use of tooth wear and damage to infer dietary change in ancient organisms. Kennedy is a leading expert in the taxonomic identification and archaeology of fish bones in the Gulf of Mexico. The supervisors have collaborations and strong links into the international archaeological and palaeontological communities, and you will undertake data collection visits to overseas collaborators in New Orleans and elsewhere in the USA.


Further details

Enquiries to: Eric Guiry, University of Leicester,

Possible timeline

Year 1

Basic training in research skills as well as familiarization with literature and existing datasets. Develop sampling strategy.

Year 2

Collect specimens during visit to New Orleans, USA. Begin isotopic and tooth microwear analyses at Leicester.


Year 3

Finish data collection. Synthesise results. Writing the thesis will take place during the final year, but papers will be published throughout the project. There will also be opportunties to give presentations at international meetings in the UK and overseas.


Further reading

DeFrance, SD, Kennedy, JR. 2020. The Finny Tribe: How coastal, cosmopolitan New Orleans satisfied an appetite for fish. International Journal of Historical Archaeology 24.2: 367-397

Guiry, E. 2019. Complexities of stable carbon and nitrogen isotope biogeochemistry in ancient freshwater ecosystems: Implications for the study of past subsistence and environmental change.” Frontiers in Ecology and Evolution 7 (2019): 313.

Guiry, E, Buckley, M, Orchard, T, et al. 2020. Deforestation caused abrupt shift in Great Lakes ecosystem. Limnology and Oceanography, 65.8: 1921-1935.

Guiry, E, Hunt, B. 2020. Integrating fish scale and bone isotopic compositions for ‘deep time’retrospective studies. Marine Environmental Research 160: 104982.

Guiry, E, Needs-Howarth, S, Friedland, et al. 2016. Lake Ontario salmon (Salmo salar) were not migratory: a long-standing historical debate solved through stable isotope analysis. Scientific Reports 6.1: 1-7.

Guiry, E, Royle, TCA, Matson, RG, et al. 2020. Differentiating salmonid migratory ecotypes through stable isotope analysis of collagen: Archaeological and ecological applications. PloS one 15.4: e0232180.

Guiry, E, Szpak, P. 2020. Quality control for modern bone collagen stable carbon and nitrogen isotope measurements. Methods in Ecology and Evolution 11.9: 1049-1060.

Guiry, E, Szpak, P, Richards, MP. 2016. Effects of lipid extraction and ultrafiltration on stable carbon and nitrogen isotopic compositions of fish bone collagen. Rapid Communications in Mass Spectrometry 30.13: 1591-1600.

Purnell, MA, Darras, LPG. 2015. 3D tooth microwear texture analysis in fishes as a test of dietary hypotheses of durophagy. Surface Topography: Metrology and Properties 4.1: 014006.

Vanderkooy, SJ. 2006. The sheepshead fishery of the Gulf of Mexico, United States: a fisheries profile Ocean Springs, Mississippi: Gulf States Marine Fisheries Commission. Fishery Profile Publication 143



The University of Leicester has clear and effective guidelines and risk assessments that have allowed for safe overseas data collection during the pandemic where it is essential for PhD research to progress. If prevailing conditions during this project prevent research visits to US collections, arrangements are in place for material to shipped to Leicester. Combined with the potential for major data collecting trips to be carried out in year 2 of the project, the impact of COVID-19 on the research can be mitigated.