Manatee

The Antillean manatee (Trichechus manatus manatus) is considered endangered in Mexico. Local extinctions have been documented in the northern Gulf of Mexico, and the only remaining population with a northern distribution is found in the Alvarado Lagoon System (ALS). The objective of this study was to determine manatee distribution in ALS. The system covers an area of 267,010 ha and includes hundreds of lagoons, floodable areas, and dozens of rivers. To detect manatees, systematic line transects were done in a boat 7.6 m in length, totaling 332.6 h of search effort with an average of 7.38 h d–1 in 45 surveys. There was a total of 13 manatee sightings: seven direct sightings, five with hydrophones, and one with a side-scan sonar. For each record the geographical coordinates were taken and integrated in a geographical information system to analyze their distribution. Manatee distribution was not uniform throughout the study area. Manatees were sighted in very specific areas of ALS cons...

The most emblematic mammal in the Alvarado Lagoon System (ALS) is the West Indian manatee (Trichechus manatus manatus). In July 1975 was considered as endangered species by the Convention on International Trade in Endangered Species of Fauna and Flora (CITES), since 1982 as a vulnerable species by the International Union for Conservation of Nature (IUCN) and is considered an endangered species under Mexican laws. The manatee is a poorly studied animal in the state of Veracruz because in natural conditions are very difficult to observe. This species is reported as extinct in the northen region of Veracruz and recent observations indicate that the manatee population that survives in this area took refuge in the lagoons system Alvarado. Alva- rado is a site with high biodiversity, coastal lagoons, and composed of more than 100 lakes and several rivers inland. We sought to establish the benefits of considering the manatee as a focal species to use as a charismatic species or flag in a conservation effort and run as an umbrella species.

Using morphometric data (body lengths, girths and weights) from 110 healthy Florida manatees ranging in size from 98 cm to 379 cm and captured for health assessments from 3 locations around Florida, we compared multiple combinations of straight and curved line lengths with girths at the axilla, umbilicus, anus and peduncle to devise a linear regression algorithm to predict the weight of an animal.

The use of this formula will benefit biologists and veterinarians by allowing for calculation of weight without endangering handlers or animals, and expedite field based health assessments to quickly return the animal to the water.

Knowledge about the distribution and abundance of the manatee (Trichechus manatus) along the coast of the Mexican state of Veracruz is scarce. Since few studies have been undertaken in this area, boat-based surveys and interviews with local fishermen were carried out to determine if there are remaining herds of manatees in the vicinity of the coastal towns of Tamiahua, Tuxpan, Tecolutla, and Casitas-Nautla. All of the fishermen interviewed noted that they used to see large herds of manatees in the area. Seventy-four percent (371 fishermen) of the survey respondents had not seen a manatee over the last 10 years, and 26% (131 fishermen) responded that the last time they saw large or small groups of manatees was in 1986 and 1995, respectively. However, since 1996, none of the fishermen had observed any manatees in the area. Similarly, no manatees were observed during the boat-based surveys (effort of approximately 1200km). It is almost certain that anthropogenic influences have altered manatee habitat significantly and thus affected the numbers of animals using the area. Also, fishermen speculated that natural phenomena such as cyclones, flooding, and storms caused manatees to move away from the area. More surveys along the coast of Veracruz are needed to determine if manatees still occur in this Mexican state. Also, it is urgent to implement conservation measures in the northern range of the manatee in Mexico to ensure the survival of this species along its original distribution.
RESUMEN: El conocimiento sobre la distribución y la abundancia del manatí (Trichechus manatus) a lo largo de la costa del estado de Veracruz, México, es pobre debido a que se han hecho muy pocos estudios en esta área. Por esta razón, se realizaron navegaciones en busca de manatíes y entrevistas con los pescadores locales para determinar si aún existen manadas de manatíes en las aguas costeras de las poblaciones de Tamiahua, Tuxpan, Tecolutla, y Casitas-Nautla. Todos los pescadores entrevistados señalaron que antes se observaban grandes grupos de manatíes en el área. De los pescadores entrevistados, el 74% (371 pescadores) respondieron que no han visto manatíes desde hace 10 años, y el 26% (131 pescadores) respondieron que la última vez que vieron a un grupo grande o a un grupo pequeño fue en 1986 y 1995 respectivamente. Sin embargo, desde 1996, ninguno de los pescadores ha observado manatíes en el área. De igual manera, no se observaron manatíes durante los recorridos en lancha (esfuerzo de aproximadamente 1200km). Es casi seguro que las actividades antropogénicas han alterado el hábitat de estos organismos de una manera significativa y por lo tanto el número de animales utilizando el área. Se necesitan más navegaciones a lo largo de la costa de Veracruz para determinar si los manatíes aún se encuentran en las aguas de este estado mexicano. Así mismo, es urgente implementar medidas de conservación en la parte norte del rango de distribución en México de estos organismos para garantizar su supervivencia a lo largo de la distribución original de esta especie.

ABSTRACT. The Antillean manatee (Trichechus manatus manatus) is considered endangered in Mexico. Local extinctions have been documented in the northern Gulf of Mexico, and the only remaining population with a northern distribution is found in the Alvarado Lagoon System (ALS). The objective of this study was to determine manatee distribution in ALS. The system covers an area of 267,010 ha and includes hundreds of lagoons, floodable areas, and dozens of rivers. To detect manatees, systematic line transects were done in a boat 7.6 m in length, totaling 332.6 h of search effort with an average of 7.38 h d–1 in 45 surveys. There were a total of 13 manatee sightings: seven direct sightings, five with hydrophones, and one with a side-scan sonar. For each record the geographical coordinates were taken and integrated in a geographical information system to analyze their distribution. Manatee distribution was not uniform throughout the study area. Manatees were sighted in very specific areas of ALS considered part of their habitat, mainly in areas with inland water bodies, in some estuarine and marshy areas, and in some wetlands with vegetation generally in appropriate condition. This lagoon system is very important for manatee conservation since it is the last site with viable populations in Veracruz and the northern Gulf of Mexico.

RESUMEN. El manatí antillano (Trichechus manatus manatus) es considerado una especie en peligro de extinción en México. En la zona norte del golfo de México se han documentado extinciones locales, y se sabe que la población remanente con distribución más norteña se encuentra en el Sistema Lagunar de Alvarado (SLA). El objetivo de este estudio fue determinar la distribución del manatí en el SLA. El sistema presenta una extensión de 267,010 ha que incluyen cientos de lagunas, áreas inundables y docenas de ríos. La localización de los manatíes se realizó mediante muestreos en transectos lineales sistemáticos en una lancha de 7.6 m de eslora. El esfuerzo de muestreo fue de 332.36 h, con un promedio de 7.38 h d–1 en 45 recorridos. En total se obtuvieron 13 avistamientos de manatíes: siete observados de manera directa, cinco detectados mediante el uso del hidrófono y uno mediante el uso de una ecosonda. En cada registro se tomaron las coordenadas geográficas y se integraron a un sistema de información geográfica para analizar su distribución. La distribución del manatí no se dio de manera uniforme en el área de estudio. Los manatíes se observaron en áreas muy específicas dentro del SLA, consideradas como parte de su hábitat, principalmente en zonas que cuentan con cuerpos de agua interiores, algunas otras áreas estuarinas y palustres, y algunos humedales generalmente con una vegetación en condiciones apropiadas. El SLA es de suma importancia para la conservación de los manatíes, ya que es el último sitio con poblaciones viables en Veracruz y en el norte del golfo de México.

Assessing the body condition of wild animals is necessary to monitor the health of the population and is critical to defining a framework for conservation actions. Body condition indices (BCIs) are a non-invasive and relatively simple means to assess the health of individual animals, useful for addressing a wide variety of ecological, behavioral, and management questions. The Antillean manatee (Trichechus manatus manatus) is an endangered subspecies of the West Indian manatee, facing a wide variety of threats from mostly human-related origins. Our objective was to define specific BCIs for the subspecies that, coupled with additional health, genetic and demographic information, can be valuable to guide management decisions. Biometric measurements of 380 wild Antillean manatees captured in seven different locations within their range of distribution were obtained. From this information, we developed three BCIs (BCI1 = UG/SL, BCI2 = W/SL3, BCI3 = W/(SL*UG2)). Linear models and two-way ...

Belize contains important habitat for Antillean manatees (Trichechus manatus manatus) and provides refuge for the highest known population density of this subspecies. As these animals face impending threats, knowledge of their dietary habits can be used to interpret resource utilization. The contents of 13 mouth, six digestive tract (stomach, duodenum and colon) and 124 faecal samples were microscopically examined using a modified point technique detection protocol to identify key plant species consumed by manatees at two important aggregation sites in Belize: Southern Lagoon and the Drowned Cayes. Overall, 15 different items were identified in samples from manatees in Belize. Five species of seagrasses (Halodule wrightii, Thalassia testudinum, Ruppia maritima, Syringodium filiforme and Halophila sp.) made up the highest percentage of items. The red mangrove (Rhizophora mangle) was also identified as an important food item. Algae (Ulva sp., Chara sp., Lyngbya sp.) and invertebrates ...