Distribution and home range of bottlenose dolphins (Tursiops truncatus) off Veracruz, Mexico
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Redalyc · Ciencias Marinas
With the goal of gathering ecological data to develop future cetacean management and conservation plans, the distribution, home range, and residency of bottlenose dolphins (Tursiops truncatus) were studied in the central-north Mexican Gulf of Mexico. Between July 2005 and June 2008, 59 boat surveys...
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| Published in: | Ciencias Marinas |
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| Main Author: | |
| Format: | Artículo científico |
| Language: | en |
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Universidad Autónoma de Baja California
2011
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| Summary: | With the goal of gathering ecological data to develop future cetacean management and conservation plans, the distribution, home range, and residency of bottlenose dolphins (Tursiops truncatus) were studied in the central-north Mexican Gulf of Mexico. Between July 2005 and June 2008, 59 boat surveys were carried out for a total of 313 h of effort at sea. During these surveys, 471 individuals were observed in 88 different groups. Photographs of naturally marked animals resulted in 275 different individuals photo-identified. Their distribution was homogeneous throughout the study area at a mean distance from the coast of 2.5 km (SD = 2.9, n = 471) and depths less than 20 m. Of the total of dolphins identified, 202 (73%) had a low sighting rate and were considered transients, whereas 34 individuals (12%) had medium and high sighting rates and were considered resident animals. At the population level, home range estimates calculated using the minimum convex polygon method showed a mean of 2771 ± 1116 km2. Using the adaptive kernel method, the mean size of home range was 1199 ± 143 km2, with five core areas identified. These areas decreased in size during the rainy season because dolphins remained close to the river plumes. At individual level, the mean home range was 129.2 km2 (n = 66), concurring with other reports from the Gulf of Mexico (Texas and Florida) in spite of habitat differences. The main component determining the size of the home range was the presence of rivers, rather than the geomorphology of the coast.
Con la finalidad de generar datos ecológicos que sirvan para futuros planes de manejo y conservación de cetáceos, se estudiaron la distribución, el ámbito hogareño (AH) y la residencia de las toninas (Tursiops truncatus) en el centro-norte de la parte mexicana del golfo de México. De julio de 2005 a junio de 2008 se realizaron 59 navegaciones con un esfuerzo de navegación de 313 h. Se observaron 471 individuos en 88 grupos diferentes y se fotoidentificaron 275 individuos diferentes. Su distribución fue homogénea a través de la zona de estudio a una distancia promedio de la costa de 2.5 km (DE = 2.9, n = 471) y a menos de 20 m de profundidad. Del total de individuos fotoidentificados, 202 (73%) presentaron una tasa de avistamiento baja y fueron considerados transeúntes, mientras que 34 individuos (12%) tuvieron tasas de avistamiento medias y altas, y fueron considerados residentes. Las estimaciones del ambito hogareño a nivel poblacional calculadas con el modelo del polígono mínimo convexo mostraron un promedio de 2771 ± 1116 km2. Con el uso del modelo adaptativo de kernel, el tamaño promedio del ambito hogareño fue de 1199 ± 143 km2 con cinco áreas núcleo determinadas. Estas áreas núcleo disminuyeron su tamaño durante la época de lluvias debido a que los delfines permanecieron cerca de las plumas de los ríos. A nivel individual, el ambito hogareño promedio fue de 129.2 km2 (n = 66), coincidente con otros registros del golfo de México (Texas y Florida) a pesar de las diferencias de hábitat. El principal componente que influyó en el tamaño del ambito hogareño fue la presencia de ríos, más que la geomorfología de la costa. |
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