Analysis of sheepshead bones by researchers at the University of New Orleans has unearthed information they say can help guide policymakers facing the critical challenge of overfishing in the Gulf of Mexico, which is an important fishery that provides food and livelihoods to many in Louisiana and beyond.
The research, conducted by UNO anthropology professor Ryan Gray, earth and environmental sciences professor Martin O’Connell and anthropology research associate Ryan Kennedy, uses size estimation and stable isotope analysis of archaeological sheepshead bones from New Orleans to identify two previously unknown, but important, overfishing events in Gulf waters.
The work not only highlights the history of fishing in New Orleans but also has important conservation implications for fish in southeastern Louisiana and the broader Gulf of Mexico, the researchers said.
“Our findings indicate that sheepshead have to be considered in broader conservation plans, as any efforts to protect other species in the Gulf of Mexico could potentially lead to increased pressure on sheepshead, which we now know are susceptible to overfishing,” Kennedy said.
While sheepshead might appear plentiful and are overlooked by many in New Orleans compared to the popular red drum species, sheepshead are likely to come under increased fishing pressure if or when commercial fishers are unable to harvest other fish in Louisiana and other Gulf of Mexico waters, researchers said.
“At the end of the day, our results serve as a reminder that policy needs to consider ecosystems as a whole and not just individual species,” Kennedy said.
That research, conducted in conjunction with researchers at the University of Leicester in England and Trent University in Canada, has been published in the journal Science Advances.
Researchers say overfishing is a critical challenge today but that policy makers and environmental scientists are often hampered by a lack of empirical data about fisheries prior to the mid-20th century.
Archaeological fish bones offer a unique view into historical fisheries and past human impacts to fish populations that can extend baseline data about the health of fish species hundreds or thousands of years in the past.
“In this case, our analysis of sheepshead bones provides the earliest evidence of overfishing of this species in the Gulf of Mexico, indicating that not only are sheepshead vulnerable to overfishing but also that modern sheepshead populations in Louisiana may still be recovering from past overfishing,” said Kennedy, a zooarchaeologist whose expertise is in analyzing animal bones.
“Knowing about past overfishing of sheepshead can help inform future policy decisions.”
The research also showed how rising urban populations drove increased demand for sheepshead that ultimately led to overfishing in surrounding waters, said Kennedy, who describes sheepshead as the “fish that fed New Orleans,” particularly in the 18th and 19th centuries.
“To me, one of the most interesting results of this research is that the expansion of fishing locations beginning in the 1820s and the subsequent quick crash of new sheepshead populations corresponds with a period of extended population growth in New Orleans,” Kennedy said. “New Orleans' urban population grew 366% between 1830 and 1860!”
“Aside from documenting previously unknown overfishing of sheepshead in the past, our results also show how rising urban populations drove increased demand that ultimately led to overfishing in surrounding waters.”
The recent study is part of ongoing research by Gray, O’Connell and Kennedy using archaeological fish bones to examine changes in fishing practices over the past 2,500 years in the New Orleans area.
Most of the sheepshead bones analyzed in the study are curated at UNO by Gray and many were recovered from archaeological sites in New Orleans by Gray and his students as part of archaeological sites around the city, such as the Passebon Cottage and 810 Royal Street.
Gray, a leading expert in the archaeology of New Orleans, was responsible for determining what time period sheepshead bones dated from by examining site histories and the kinds of artifacts recovered from each site.
O’Connell is an expert on the various fish species of southeast Louisiana and helped the team interpret the archaeological data in the context of modern fish ecology in the area. For example, a chemical analysis of sheepshead bones showed that some sheepshead from the mid-19th century had a chemical signature unique to fish living in seagrass beds.
O’Connell’s knowledge of southeast Louisiana fish ecology was critical in connecting these data with historic fishing activities in the Chandeleur Islands and other nearby locations where seagrass is common.
Kennedy’s work focused on identifying all sheepshead bones at the study sites by comparing archaeological fish bones to modern fish skeletons from known species, many of which were collected by O’Connell and his students.