Analyses of historical documents reveal past trends of exploitation of manatees (Trichechus inunguis) in the Amazon Basin (16th-19th centuries)

The West Indian manatee ( Trichechus manatus) and the Amazonian manatee ( Trichechus inunguis) have been exploited by different societies from ancient times to the present. Deploying the matrix of Indigenous knowledge and uses, the hunting of manatees was at the core of European colonisation strategies of the Americas within a framework of appropriation, use, and consumption of aquatic mammals spanning the (post)colonial period. Today, both species are listed by the International Union for the Conservation of Nature and Natural Resources (IUCN) as Vulnerable, and population trends are expected to decrease in the future. While the exploitation of manatees (in particular, T. inungis) is well described in the 20th century, no overall quantitative assessments of such exploitation in the preceding centuries have been made. Here, we address this gap of knowledge through a systematic review of the literature, identification and review of documentary sources, selection and extraction of quantitative data, and contextual analysis through cross-analysis of historical documents of several types. Our quantitative estimates resulted in a total of 14.030 individuals captured, which are most probably largely underestimated. It corresponds to a biomass removal of 6.248,9 tonnes in a period of non-continuous 52 years between the 16 ^th and the 19 ^th centuries. Specifically, an average of c. 14.000 manatees were hunted between 1843 and 1898, comprising 91% of all captures prior to the twentieth century when another point of accelerated extraction occurred. We determined a trend of increasing captures from the 17 ^th to the 20 ^th centuries, for Brazil, but an important lacuna of data for the 16 ^th century, and pre-European contact, persists. However, the results inform current and future conservation measures for the species, while also including historical, cultural, traditional, and indigenous perspectives about the use of aquatic resources.