Historical Range Contraction and Extent of Harbour Porpoises ( <i>Phocoena phocoena</i> ) in the Baltic Sea Revealed by Archival Newspapers

ABSTRACT Over the past several centuries, the Baltic Proper harbour porpoise ( Phocoena phocoena ) has undergone significant population declines, resulting in its current IUCN classification as critically endangered. While conservation efforts are extensive and multinational, the population's abundance has only been estimated once (SAMBAH Project, 2011–2013). Ad hoc historical sources and the sub‐fossil archaeological record, dating to 7000 years BP, suggest that the population once had a wider distribution in the Baltic Sea. However, the historical abundance and distribution of the Baltic Proper harbour porpoise population remain largely unknown, especially before the mid‐20th century. This study examines archival Swedish newspaper records from the late 1700s to the early 1900s to assess the presence and distribution of porpoises. Digitized articles were searched for by keyword in the National Library of Sweden Newspaper Archive. This dataset was combined with HELCOM/ASCOBANS historic data. The records show that harbour porpoises historically occurred regularly along the entire Swedish coast, including the northernmost parts of the Gulf of Bothnia, where the species is virtually absent today, suggesting a notable range retraction. While harbour porpoises appeared less frequently in the Baltic Sea than along the west coast of Sweden, the number of Baltic records indicates that porpoises occurred more frequently than today. The peak occurrence of porpoises during spring and summer suggests that the Gulf of Bothnia historically constituted an important foraging habitat for animals migrating from the southern Baltic. By integrating historical records with modern conservation data, this study provides critical insights into the long‐term effects of human activity on the Baltic Proper harbour porpoise. Understanding past ranges and approximate population size is vital for guiding more effective conservation strategies.