SARAWAK FIREFLIES: Sungai Raan Display Trees Revisited 11 Feb 2019

Sungai Raan is 20 kilometers Southwest of Miri. Two kilometer of river was surveyed in 2010 as part of our CFZ project. To make a new fireflies display tree survey at Sungai Raan river is very important. The general feeling is that Miri firefly populations are dwindling. The baseline and first night time assessment of Fireflies at Sungai Raan was done on the 06th Jan 2010.

The finding were the river have a two sections bearing fireflies display trees. Upper section is a long shore river system and going up near the bridge of the main road and lower section is close to the river mouth.

Upper Section the round one done in 2010 the upside down tears 2019 display trees

The 2010 survey showed the lower section having 13 display trees and the lower section having 8 display trees.

Lower Section the round one done in 2010 the upside down tears 2019 display trees

After 8 years since the last survey at this river, there is a need to revisit the river to find out if there are any changes to the display trees discovered in the last survey. The area at the estuary showed some indications of development : shop-houses and a new water front. This is a treat to the first section of the river where the fireflies display trees are located. The middle section is a concentration of housing with jetties for fishing boats some servicing the nearby houses. Now there is also a swift-let house which are becoming more common.

We have an opportunity to come back to the river on the 11 Feb 2019 with students University Kebangsaan Malaysia interested to study Petrotyx tener. I was very pleased to have with me two students and a professor on this trip to Sungai Raan.

The day of choice is very good for a firefly look and see, having a 30% waxing crescent and a neap tide period. A neap tide is a bit risky for the boat to maneuver because of the shallow river bed. We booked a boat a week earlier from Rahman Jemin. We set our meeting at 5 pm so that we could have a day time tree survey taking note of the types of trees that line up the river. It is a surprise to me to see the Bakam river bank being turned into a beautiful waterfront. The boat landing is at Bakam river. Sungai Raan shares the same estuary with Sungai Bakam.

Sungai Bakam waterfront

As we ride along Sungai Bakam towards the estuary we entered Sungai Raan we saw a huge round building under construction in front of the river mouth. We entered Sungai Raan and took notes of mangroves tree types that line the river bank. Not much changes seen along the river if it was not for the swiftlet farm. We finished the daytime tree survey and returned into Sungai Bakam jetty. We took our dinner at the food stall nearby.

The dinner was good, at around 7:30 pm we went to Bakam jetty and headed into Sungai Raan. I was a bit nervous when I didn't notice the first couple of display trees. However when we crossed under the bridge I saw a twinkling of sporadic flashes of fireflies at the left side of the river just at the end of the bridge. I was very happy to see this first fireflies display tree. Soon we passed six display trees. The population was not many, only between 10 and 20 individuals. The last display tree is the same tree that was recorded in 2010.

We passed the mid section and the area did not bear any fireflies despite a few caseolaris and rhizophora trees. We passed quickly along this section. At the upper section we passed 3 old display tree void of fireflies. The 4th tree having the first display and we went along until we reached a shallow section. This section only bore six display trees. Wind-speed , water ph and salinity and temperature were recorded at all sampling points. We finished our survey at around 9:30 pm and drove back to Miri.