Sperm Whale Catches and Encounter Rates during the 19th and 20th Centuries

On a global scale, the number of sperm whales caught during the 20th century greatly exceeded the 19th-century catch. However, in at least two whaling grounds – the Japan Ground in the central North Pacific and the Galápagos Ground in the eastern tropical Pacific – the rate at which American whalers encountered sperm whales during the 19th century declined rapidly over the years, suggesting significantly decreased whale abundance (Bannister et al, 1981; Hope and Whitehead, 1991). The discrepancy can be seen in Figure 9.1, which shows catches peaking and encounter rates declining markedly in the 19th century, with catches peaking again at much higher levels in the 20th century. Declines in encounter rates during the 19th century seem inconsistent with the fact that much larger catches were made on these and in adjacent regions during the 20th century (Tillman and Breiwick, 1983; Whitehead, 2002). Figure 9.1 Estimated annual global removals of sperm whales, circa 1750–2000, and encounter rates in the mid-19th century https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781849772105/2bb59cdc-c776-452a-8dd5-5607e5d337a7/content/fig9_1_B.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> Note: Encounter rates from 19th-century whaling are denoted by closed circles on the Japan Ground and open circles on the Galápagos Ground. Source: Japan Ground encounter rates from Bannister et al (1981); Galápagos Ground encounter rates from Hope and Whitehead (1991); 19th-century catches from Best (2005); 20th-century catches from International Whaling Commission; view colour version at https://www.hull.ac.uk/oceanspast" xmlns:xlink="https://www.w3.org/1999/xlink">www.hull.ac.uk/oceanspast