Manatee Mortality in Puerto Rico

Abstract

/ The most pressing problem in the effective management of the West Indian manatee (Trichechus manatus) in Puerto Rico is mortality due to human activities. We assessed 90 cases of manatee strandings in Puerto Rico based on historical data and a coordinated carcass salvage effort from 1990 through 1995. We determined patterns of mortality, including type of event, condition of carcasses, spatial and temporal distribution, gender, size/age class, and the cause of death. The spatial distribution of stranding events was not uniform, with the north, northeast, and south coasts having the highest numbers. Six clusters representing the highest incidence included the areas of Fajardo and Ceiba, Bahía de Jobos, Toa Baja, Guayanilla, Cabo Rojo, and Rio Grande to Luquillo. The number of reported cases has increased at an average rate of 9.6%/yr since 1990. The seasonality of stranding events showed a bimodal pattern, from February through April and in August and September. Most identified causes of death were due to human interaction, especially captures and watercraft collisions. Natural causes usually involved dependent calves. From 1990 through 1995, most deaths were attributed to watercraft collisions. A reduction in anthropogenic mortality of this endangered species can be accomplished only through education and a proactive management and conservation plan that includes law enforcement, mortality assessment, scientific research, rescue and rehabilitation, and inter- and intraagency cooperation.

Strandings of Antillean manatees, <i>Trichechus manatus manatus</i>, in northeastern Brazil

“…A similar analysis done by Mignucci-Giannoni et al (2000) on the frequency of manatee strandings in Puerto Rico showed that those events were more common in March and October, with 30% occurring during summer. Our experience with captive animals indicated that calves were extremely sensitive to alterations in the environment.…”

“…Mignucci-Giannoni et al (2000) recorded 90 cases of manatee strandings in Puerto Rico from 1990 through 1995. Whereas those studies included adult animals, all the live stranded Antillean manatees (Trichechus manatus manatus) in northeastern Brazil were of dependent calves (mean TL = 155.7cm; range: 109-245cm).…”

The Role of Small Islands in Marine Subsistence Strategies: Case Studies from the Caribbean

“…For example, it is now known that large herbivores such as turtles (Carrillo et al 1999) and manatees (see McKillop 1985;Mignucci-Giannoni et al 2000), as well as numerous carnivores, are ecologically extinct on Caribbean seagrass beds and coral reefs, with food chains "now dominated by small fishes and invertebrates" (Jackson 1997: S28).…”

Disseminated toxoplasmosis in Antillean manatees Trichechus manatus manatus from Puerto Rico

“…A complete necropsy, following an established procedure (Bonde et al 1983(Bonde et al , 2012, was performed on each carcass. Age classification was based on standardized total straight length measurements specific to Antillean manatees: adult (> 225 cm), subadult (176 to 225 cm) and calf (<176 cm) (Mignucci-Giannoni et al 2000). Tissue sections from the lung, heart, liver, spleen, superficial and deep lymph nodes, stomach, pancreas, small intestine, colon, kidney and reproductive tract were collected for histologic examination from all manatees.…”