Causes of Mortality for Endangered Antillean Manatees in Cuba

Abstract

The Antillean manatee is categorized as endangered by the International Union for the Conservation of Nature primarily due to its low abundance. Further declines in abundance are expected due to a group of human related threats that include illegal hunting, fatal interactions with fishing gear, increasing watercraft traffic, and pollution. The nature of current threats is not well described for every critical population of manatees. In particular, threats to manatees have not been documented or evaluated in a systematic manner in coastal waters surrounding Cuba, which is a major reason why plans specifically addressing conservation of manatees in Cuba have not been implemented. To address this lack of information, we assessed patterns in various threats by reviewing reports of stranded (alive or dead) and captured manatees, with some reports being historical and others consistently available since 2001. For 94% of the contemporary cases, carcasses of dead animals were reported; the remainder (6%) involved live manatees and subsequent efforts to rescue and rehabilitate them. Documented causes of mortality included poaching (38%), entanglement in fishing gear (10%), deaths of dependent calves (2.5%), and boat collisions (2.5%). The cause of death for the remaining 47% of reports could not be determined. Mortalities were highest in areas with intensive commercial fishing effort, and mortalities in marine protected areas indicated a need for improved management. These initial findings provide the first estimates of the magnitude of mortality of manatees in Cuba and yield valuable insights into the causes of deaths. The existence of intense and poorly regulated fishing in certain areas, including protected areas, represents a potentially significant threat to manatees. The effects and management of this activity, especially in habitats that are critical for manatees, merit further attention.

Stranding reports of the Antillean manatee in the middle Magdalena Basin, Colombia 2011 to 2023

“…A finding that draws attention in the results from this study is the high incidence of dead females compared to males; these data coincide with what was discovered in historical mortality events in countries such as Cuba (Álvarez-Alemán et al, 2021), Colombia (Montoya-Ospina et al, 2001), and Belize (Castelblanco-Martínez et al, 2018). This phenomenon is discouraging due to the crucial role that females play in the survival of the species (Álvarez-Alemán et al, 2021).…”

“…The incidence by age category in stranded manatees from Colombia was higher in adult and juvenile animals than calves. This information differs from that reported in the same species throughout countries such as Cuba (Álvarez-Alemán et al, 2021), Belize and Mexico (Castelblanco-Martínez et al, 2018), Brazil (Balensiefer et al, 2017), Colombia (Montoya-Ospina et al, 2001), and Puerto Rico (Mignucci-Giannoni et al, 2000, where the highest incidence is represented by calves and juveniles. The fact that the mortality events in Colombia are associated with adult manatees could generate a disadvantage for the population that is distributed in the Magdalena River basin because those are individuals of reproductive age, and without their contribution the population could be decreasing, resulting in a bottleneck and loss of genetic variability (Luna et al, 2021).…”

Widespread Use of Migratory Megafauna for Aquatic Wild Meat in the Tropics and Subtropics

“…West Indian manatees are also hunted opportunistically (e.g., as bycatch in fishing nets) and directly targeted throughout the Caribbean, in the Magdalena and Orinoco River systems, and the Maracaibo Lake system (Montiel-Villalobos and Barrios-Garrido, 2005;Romero and Creswell, 2005;Vail, 2005;Castelblanco-Martínez et al, 2009. They were hunted historically for oil, bones, and meat (e.g., O'Shea et al, 1988), but today hunting is exclusively for meat, a practice considered a significant threat in Brazil, Colombia, Costa Rica, Cuba, Dominican Republic, French Guiana, Guatemala, Honduras, Mexico, Suriname, Trinidad, and Venezuela (Self-Sullivan and Mignucci-Giannoni, 2012;Alvarez-Alemán et al, 2021). Killing of bycaught animals for consumption occurs in Colombia, Dominican Republic and Haiti (Kiszka, 2014).…”

Increasing mortality of Endangered Antillean manatees Trichechus manatus manatus due to watercraft collisions in Belize

“…Though protected, Antillean manatees face many anthropogenic threats that have resulted in reduced and isolated populations in the Caribbean, including poaching, habitat degradation and loss, watercraft collision, entanglement in fishing gear, and pollution (Mignucci-Giannoni et al 2000, Hunter et al 2010, Balensiefer et al 2017, Alvarez-Alemán et al 2021). In Belize, there have been increasing numbers of manatee strandings resulting from collisions with the hulls or propellers of watercraft (Galves et al 2013(Galves et al , 2023, likely exacerbating documented population declines for this subspecies; however, very little is known about the nature of this emerging threat and its direct repercussions for the manatee population in Belize (Castelblanco-Martínez et al 2012).…”