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Study finds 43pc decrease in dolphin population across Sindh

Updated August 01, 2013

KARACHI, July 31: A recent study has shown that there has been a 43 per cent reduction over the past five years in the population of Indus River dolphin inhabiting the area between the Guddu and Sukkur barrages.

However, there has also been a 44pc increase in the number of dolphins dwelling the area between the Taunsa and Guddu barrages over the past decade.

The study titled ‘Abundance of Indus River Dolphin (Platanista gangetica minor) in 2011 and 2012’, is conducted by the World Wide Fund for Nature-Pakistan (WWF-P) in collaboration with International Union for Conservation of Nature (IUCN), wildlife departments of Punjab, Sindh and Khyber-Pakhtunkhwa, besides the Adventure Foundation Pakistan, Nature Conservation Pakistan and the Conservation and Hunting Association of Pakistan.

According to the study, the total dolphin population in three river sections — Chashma-Taunsa, Taunsa-Guddu and Guddu-Sukkur — is estimated to be 1,262, with the Chashma-Taunsa section of the Indus River making up only 7.7pc of the total dolphin population with the lowest abundance.

The total population of freshwater dolphins reported in 2006 was 1,442.

However, a direct count of subpopulation of the dolphins living outside the Guddu and Sukkur river sections, between the Chashma and Taunsa barrages, showed an increase of 5.75pc in the past five years, says the study.

“A stable sub-population between the Chashma and Taunsa barrages in 10 years is a noticeable finding of the study,” it states. “Another important feature is the estimate of sub-population between the Taunsa and Guddu barrages, the highest number of dolphins ever recorded in this section contributing about 36.8pc to the total population.”

The actual number of dolphins in this river section, according to the study, could be higher since “the direct count method underestimates the abundance because sighting probability depends on observer’s ability to see the dolphin”. Giving a plausible explanation for the increase in dolphin population, it says that it could be due to their natural growth or the result of a positive impact of high floods, allowing an exchange between sub-populations.

28 dolphins dead

The study points out that the direct count of dolphins in the Guddu-Sukkur section was found to be substantially low in 2011 surveys as compared to the 2006 records. The total population of the species in this river section was estimated to be 857.

The Guddu-Sukkur river section (the prime habitat of the freshwater dolphin), according to the report, contributed the highest number (55.5pc) to the total abundance of the species. However, the river section also reported the highest dolphin morality (28) in 2011 year, which, according to the report, could be one reason for low population estimates.

Highlighting the risks to the species, the study says that the Indus River dolphin is one of the world’s most threatened cetaceans. The most critical threat it faced was direct mortality caused due to accidental entanglement in fishing nets.

“Over the past two years, significant increase has been observed in illegal fishing practices in the area between the Guddu and Sukkur barrages,” says the report. “This involves the use of pesticides to maximise fish catch. Altered fishing system in Sindh under which an increasing number of people are being awarded fishing licenses has also encouraged illegal fishing activities, subsequently endangering dolphin population.”

Water pollution, according to the report, is another serious threat to the existing population. In low-water season when less area is available for the species, the quality of available habitat is deteriorated.

“The Indus River is surrounded by agricultural land on both banks. Heavy use of pesticides and fertilizers on agricultural lands contaminate the river through runoff water, consequently, polluting the habitat of Indus River dolphin.”

Referring to a study conducted by Husein Ibrahim Jamal Research Institute of Chemistry of Karachi University, the report says that the traces of pesticides (cypermethrin, deltamethrin, endosulfan and DDT) had been found in samples of liver, blubber and kidney of the fish indicating the use of these chemicals in agricultural lands along the river. “The river section between the Guddu and Sukkur barrages represents the highest subpopulation for Sindh province whereas the second largest subpopulation is found between the Taunsa and Guddu barrages. It is recommended that the stretch of the Indus River between the Taunsa and Guddu barrages be declared a protected area,” the study suggests.

It also calls for a national conservation initiative for the alarming increase in dolphins’ mortalities in the Guddu-Sukkur river section.

“Observations have shown that the high mortality rate of dolphins is directly associated with an increase in illegal fishing practices (in Sindh). It is of vital importance to amend fisheries regulations and control illegal fishing activities in the core habitat of the species. Provincial fisheries legislations need serious attention and should be revised for overall benefit of the Indus River freshwater ecosystem and its associated biodiversity,” the report adds.