Historical specimens and photographs reveal long‐term changes in Smalltooth Sawfish (Pristis pectinata) age class distribution and average size during U.S. population decline

Abstract

Population‐level, historical studies can provide insights on the distribution, abundance and demographic characteristics of imperiled species prior to human exploitation, habitat modification or climate change. These studies provide a baseline for contemporary data, which often shape successful management and recovery. The smalltooth sawfish (Pristis pectinata) occupies ~20% of its historical range due to declines driven primarily by mortalities in fisheries and coastal habitat loss over the last century. As a result, they are listed as Critically Endangered on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species and as Endangered federally in the United States (U.S.). Because P. pectinata grow to a large size and have a toothed rostrum, many historical photographs and specimens are archived in natural history collections. Metadata and morphometric data were collected and analysed from P. pectinata photographs (n = 84) and specimens (n = 429) to evaluate temporal changes in average size and historical distribution of five age classes in U.S. waters. Historically, smaller age classes were well‐distributed throughout the northern Gulf of Mexico, while only larger age classes were recorded on the U.S. east coast, north of Florida. All age classes were found in both Florida and Texas historically, but records from Texas decline after the 1980s and remain persistent in Florida, indicative of a strong‐hold for the U.S. population. Regardless of origin, individuals in three of the five age classes were larger on average historically than those observed today. Understanding which age classes used previously occupied areas will help direct habitat restoration efforts and support recovery, especially in the face of climate change. Non‐traditional data sources, such as those used here, may often be the only means of providing historical context to modern research on imperiled species, ultimately guiding restoration and conservation efforts.