To resolve the population genetic structure and phylogeography of the West Indian manatee (Trichechus manatus), mitochondrial (mt) DNA control region sequences were compared among eight locations across the western Atlantic region. Fifteen haplotypes were identified among 86 individuals from Florida, Puerto Rico, the Dominican Republic, Mexico, Columbia, Venezuela, Guyana and Brazil. Despite the manatee's ability to move thousands of kilometers along continental margins, strong population separations between most locations were demonstrated with significant haplotype frequency shifts. These findings are consistent with tagging studies which indicate that stretches of open water and unsuitable coastal habitats constitute substantial barriers to gene flow and colonization. Low levels of genetic diversity within Florida and Brazilian samples might be explained by recent colonization into high latitudes or bottleneck effects. Three distinctive mtDNA lineages were observed in an intraspecific phylogeny of T. manatus, corresponding approximately to: (i) Florida and the West Indies; (ii) the Gulf of Mexico to the Caribbean rivers of South America; and (iii) the northeast Atlantic coast of South America. These lineages, which are not concordant with previous subspecies designations, are separated by sequence divergence estimates of d = 0.04-0.07, approximately the same level of divergence observed between T. manatus and the Amazonian manatee (T. inunguis, n = 16). Three individuals from Guyana, identified as T. manatus, had mtDNA haplotypes which are affiliated with the endemic Amazon form T. inunguis. The three primary T. manatus lineages and the T. inunguis lineage may represent relatively deep phylogeographic partitions which have been bridged recently due to changes in habitat availability (after the Wisconsin glacial period, 10 000 B P), natural colonization, and human-mediated transplantation.

/ 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.

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An assessment of cetacean strandings was conducted in waters off Puerto Rico and the United States and British Virgin Islands to identify, document and analyse factors associated with reported mortality events. Nineteen species of cetaceans were reported stranded. The total number of events recorded between 1867 and 1995 was 129, comprising over 159 individuals. The bottlenose dolphin (Tursiops truncatus) was the species most commonly found stranded, followed by Cuvier's beaked whale (Ziphius cavirostris), sperm whale (Physeter macrocephalus), Atlantic spotted dolphin (Stenellafrontalis) and short-finned pilot whale (Globicephala macrorhynchus). An increase in the number of strandings is evident over the past 20 years, averaging 63.l% per year. Between 1990 and 1995, the average number of cases per year increased from 2.1 to 8.2. The seasonal pattern of strandings was not found to be uniform, with a high number of strandings occurring in the winter and spring. The monthly temporal distribution showed an overall bimodal pattern, with the highest number of cases reported for February, May and September. The spatial distribution was not even, and differed between countries, within countries, and between taxonomic groups and species. Aside from undetermined causes of mortality, the ratio of natural causes in relation to human-related causes was of 1.2:1. Between 1990 and 1995, a reduction of the percentage of undetermined cause of deaths resulted from the establishment of a cooperative effort in studying mortality in an organised and systematic manner. The most common natural cause of death category was dependent calf. The most common human-related cause categories observed were entanglement and accidental captures, followed by animals being shot or speared. Evaluation and recommendations to improve the research conducted are formulated, including guidelines for the development of a strategic plan to obtain baseline data on the biology and life history of cetaceans to be applied to their conservation and management.

The West Indian manatee (Trichechus manatus) is one of the most endangered species in Jamaica. Four manatees were impounded at the Alligator Hole River on the south coast of the island since 1981. Their semi-captive status was unclear and the present study reports on the documentation of their gender and survival possibilities. The river was surveyed between 18-25 June 1991 by canoeing and snorkeling, interviews were conducted and photographs and documents were examined to ascertain their status, confirm their gender determination and to assess the circumstances of their capture. A total of 10 sightings were recorded, representing three different animals, all females. They were extremely evasive of humans, as they had been mistreated for long periods of time. Two of the animals appeared healthy, but one was observed with a severe cut in its caudal peduncle, produced by a rope and net. Given Jamaicas low manatee population numbers, and the observed degradation of the river, no justification exists to hold three reproducing female manatees apart from the rest of the Jamaican manatee gene pool. It is recommended that the manatees be captured and released at sea, after fitting them with satellite radio-transmitters, which will allow monitoring their re-adaptation to the wild.Resumen El manatí de las Indias Occidentales (Trichechus manatus) es una de las especie en mayor peligro de extinción en Jamaica. Cuatro manatíes fueron encerrados en el rio Alligator Hole en la costa sur de la isla desde 1981. Su estatus de semi-cautiverio no estaba claro y nuestro estudio incluye la determinación del sexo de los animales y sus posibilidades de sobrevivencia. El río fue examinado entre el 18 y el 25 junio de 1991 utilizando canoas y a través de snorkeling, se llevaron a cabo entrevistas y se examinaron fotografías y documentos para analizar su estatus, para confirmar la determinación del sexo y evaluar las circunstancias de su captura. Un total de 10 avistamientos fueron registrados distinguiendo tres animales diferentes, todos hembras. Los animales se mostraron extremadamente evasivos de los humanos, ya que fueron maltratados por largos períodos de tiempo. Dos de los animales aparentan estar saludables, pero uno de ellos fue observado con una herida severa en su pedúnculo, producto de una soga y malla. Debido al bajo número de los individuos de la población de manatíes en Jamaica y la degradación del río, no existe justificación para mantener tres manatíes hembras en madurez reproductiva, aislados del resto del acervo genético de la especie en Jamaica. Se recomienda que los manatíes sean capturados y liberados en el mar después de colocarles radio-transmisores de satélite los cuales permitirán evaluar su re-adaptación al medio ambiente.