La ballena franca del sur, Eubalaena australis (Desmoulins, 1822) en aguas chilenas: análisis de sus registros desde 1976 a 2008
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Date
2008-12
Journal Title
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Volume Title
Publisher
Facultad de Ciencias del Mar y de Recursos Naturales, Universidad de Valparaíso
Abstract
Se analizaron los avistamientos de Eubalaena
australis en aguas chilenas entre los años 1964 y 2008. Durante
estos 44 años se han documentado 124 avistamientos con 232
ejemplares incluyendo a 39 crías. La distribución de los registros
muestra tres zonas geográficas: i) aguas al norte de los 47°S, ii)
aguas entre el estrecho de Magallanes y canal Beagle, y iii) aguas
del paso Drake y Antártica. Mensualmente, una alta frecuencia de
avistamientos se registró entre agosto y octubre. La mayoría de las
crías se registraron al norte de los 41°S, concentrándose entre los
23°S y 25°S y entre los 32° y 36°S. Los tamaños grupales variaron
entre 1 a 7 animales, registrándose en las aguas al norte de los
47°S un porcentaje levemente mayor de grupos en pares, mientras
que bajo los 47°S, los grupos estuvieron constituidos
mayoritariamente por animales solitarios. La tendencia de la
población, considerando el total de animales registrados al norte
de los 47°S, mostró una tasa de incremento positivo pero no
significativa entre los años 1976 y 2008; sin embargo, en el caso
de las crías, la tasa fue cercana a 0, sugiriéndose que ambas tasas
estarían subestimadas. En consecuencia, es de absoluta necesidad
aumentar el esfuerzo de observación de cetáceos, junto a un
programa de estudios sistemático, incluyendo la foto-identificación
y estudios moleculares, cuyos resultados permitan conocer la
ecología y parámetros demográficos necesarios para evaluar esta
especie de ballena catalogada ‘En Peligro Crítico’ en aguas
chilenas.
Sighting data of Eubalaena australis from Chilean waters from 1964 to 2008 were analyzed. During these 44 years, 124 sightings of 232 whales were recorded, including 39 calves. Whales were sighted in three main areas: i) north of 47°S, ii) Magellan Strait and Beagle channel, and iii) Drake Passage and Antarctica. A higher frequency of sightings occured between August and October. Most of calves were recorded north of 41°S, being concentrated between 23°S and 25°S, and also between 32° and 36°S. Group sizes ranged from 1 to 7 whales, in the area north of 47°S pairs were more common, while for the two areas south of 47°S, whales were most commonly sighted singly. The population trend, considering only whales north of 47°S, showed an increase (although not statistically significant) between 1976 and 2008, but when only calves were considered, there was no increase, suggesting that both rates would be underestimated. We highlight the need for an increase in sighting effort for southern right whales as well the development of a systematic program for monitoring, photoidentification and molecular study. These measures would improve the demographic knowlegde and therefore provide a sound basis for evaluation of the status of this species, which is currently considered as ‘In Critical Risk’ in Chilean waters.
Sighting data of Eubalaena australis from Chilean waters from 1964 to 2008 were analyzed. During these 44 years, 124 sightings of 232 whales were recorded, including 39 calves. Whales were sighted in three main areas: i) north of 47°S, ii) Magellan Strait and Beagle channel, and iii) Drake Passage and Antarctica. A higher frequency of sightings occured between August and October. Most of calves were recorded north of 41°S, being concentrated between 23°S and 25°S, and also between 32° and 36°S. Group sizes ranged from 1 to 7 whales, in the area north of 47°S pairs were more common, while for the two areas south of 47°S, whales were most commonly sighted singly. The population trend, considering only whales north of 47°S, showed an increase (although not statistically significant) between 1976 and 2008, but when only calves were considered, there was no increase, suggesting that both rates would be underestimated. We highlight the need for an increase in sighting effort for southern right whales as well the development of a systematic program for monitoring, photoidentification and molecular study. These measures would improve the demographic knowlegde and therefore provide a sound basis for evaluation of the status of this species, which is currently considered as ‘In Critical Risk’ in Chilean waters.
Description
Keywords
Ciencia, Ballenas, Avistamientos, Whales
Citation
RBMO 43(3): 653-668, dic. 2008