Save the Irrawaddy Dolphin Project: Day 4

Day 4: 1 May 2015 (Friday): Learning about traditional fishing methods and more dolphins sighted!

by Dr Alfonso Lopez

We set off much earlier today at around sunrise (5.45am). We had two missions to complete: to search for and identify the dolphins and to find out more about fishing techniques adopted by local fishermen.

Beautiful sunrise on Songkhla Lake

Nets, hooks and traps

We observed that fishermen here in the north lake employ a diverse range of fishing methods. Some of them use nets with a small mesh size to catch small fish. These nets are located close to the shore where Irrawaddy dolphins have never been spotted, so they are unlikely to have an impact on dolphin mortality.

We also saw fish and shrimp traps, hooks-and-lines and traditional throw nets, which are commonly used for catching catfish, tilapia, and giant freshwater shrimp, among others. These small scale fishing methods pose minimal threat to the dolphins.

Traditional hooks-and-lines used for catching catfish.

A fisherman and his traditional throw net.

What a huge freshwater prawn!

Back to spotting dolphins

After learning about these traditional fishing methods, we began our main mission of the day – dolphin spotting.

The weather was incredibly warm today and the sky was bright and clear. Without even the slightest breeze, the surface of the lake was completely still. Apart from the intense heat, these were the perfect conditions for dolphin sighting.

Following our transects looking for dolphins.

After four hours of searching we were just about to turn back, when Mr Somchai called from one of the boats to share great news: he had spotted some dolphins!

Dolphins spotted again!

An aerial view of one of the Irrawaddy dolphin pods

We immediately moved in to that area and were very excited to see around 20 Irrawaddy dolphins in 3 separate pods.

Do you see what I see? An Irrawaddy dolphin with its little dorsal fin peeking out of the water!

Like yesterday, we took some good pictures of the dolphins’ dorsal fins to add to our growing catalogue of Irrawaddy dolphin photo IDs.

Understanding dolphin behaviour

After four days of observation, I realised that the Irrawaddy dolphins tend to stay away from the shore, probably at least one kilometre away. Here are some possible factors:

  1. Depth

Using bamboo as a ruler to measure the depth of the lake.

We measured the depth of the lake several times today and concluded that our survey area is between 2 metres and 2.4 metres deep. This is not considered deep, which means the shore is even shallower, and less conducive for the dolphins to swim around.

  1. Aquatic plants

Aquatic plants commonly found on the lake surface near the shore.

There are several areas near the shore where huge masses of aquatic plants are found on the surface of the lake. As dolphins need to surface for air this could deter them from occupying these areas.

  1. Temperature

The water temperature tends to be higher along the shores. These dolphins prefer slightly cooler water which is found towards the deeper, more central section of the lake.

  1. Abundance of prey

Fish that the dolphins eat are apparently more abundant in the centre of the north lake, rather than the shorelines.

  1. Human activity

Irrawaddy dolphins tend to shy away from humans. So it is no surprise that they would avoid the shore where there are more human activities.

It has been a very exciting day today, and I look forward to see some more dolphins tomorrow on the last day of the survey.

Follow the team on their trip

Facebook Comments