WWF – Irrawaddy dolphin Project

WWF – Irrawaddy dolphin Project

Mekong River Irrawaddy dolphin Calf mortality

Year: 2007
Duration: 3 years
Partners: WWF

Project Background

The largest freshwater population of lrrawaddy dolphins occurs along the Mekong River in  Cambodia  and southern Laos.  This subpopulation  is classifled as  Critically Endangered  by  the IUCN with estimates  of 80-100  individuals. Between 2001 and 2006, 72 dolphins – 60% of which were calves, died along the Mekong River. These figures underestimate true mortality as they do not reflect undetected deaths. Without understanding the etiology of dolphin mortality, extinction of the Mekong population will be unavoidable. Research to date has found that at least 64% of adult deaths are due to anthropogenic causes, particularly entanglement in fishing   gear. Measures are underway to address this and encouragingly fewer dead adults are now being found. In contrast, aetiology has only been determined for one calf. Diagnosing the cause of calf mortality is vital to designing mitigation stratagies to improve recruitment and ensure the survival of the population.

The project seeks to diagnose the cause of calf mortality, information that is critical to the long term survival of the Mekong population of lrrawaddy dolphins. Concurrently, the project will establish capacity  in  personnel and  infrastructure  that  will  ensure  that detailed investigation of lrrawaddy dolphin mortality will continue along the Mekong River in the long term.

It was documented earlier that adult Mekong Irrawaddy dolphins were by-caught in gill nets. In recent years, an increasing number of immature dolphins were found dead. Different investigations came to the conclusion that the death of young dolphins may be the result of several factors (Dove 2009).

These factors include:

  1. Disease
    1. Aeromonas hydrophila
    2. Other opportunistic bacterial infections
  2. Environmental contaminants
    1. Organic contaminants
    2. Non organic contaminants such as mercury
  3. Inbreeding depression
    1. Low genetic diversity

pdficon_largeIrrawaddy Dolphin Conservation Project – Report 2007 (PDF 976KB)

pdficon_largeEvaluation of ecotoxicological effects Irrawaddy dolphins Mekong River (PDF 1.346KB)

pdficon_largeMekong dolphins 2010-2011 (PDF 456KB)