Lee Trap Fishery Monitoring in Southern Lao PDR Reveals Fishery Resources Degrada� on from 2008 to 2013

implemented in Lao PDR at the Khone Falls (Khong District, Champasack Province) and been supported by the Mekong River Commission (MRCS) since 2005. The purpose of this monitoring is to track the abundance and diversity of migratory white fi sh in the Lower Mekong River, and to provide valuable informati on on fi sheries resources for fi sheries management. The monitoring is undertaken every year by the Living Aquati c Resources Research Centre (LARReC) during the wet season from May to September at Hou Som Yai Channel in Southern Lao PDR at the Khone Falls.

The Lee Trap Fishery Monitoring Programme is one of the four fi sheries monitoring programmes having been implemented in Lao PDR at the Khone Falls (Khong District, Champasack Province) and been supported by the Mekong River Commission (MRCS) since 2005.The purpose of this monitoring is to track the abundance and diversity of migratory white fi sh in the Lower Mekong River, and to provide valuable informati on on fi sheries resources for fi sheries management.The monitoring is undertaken every year by the Living Aquati c Resources Research Centre (LARReC) during the wet season from May to September at Hou Som Yai Channel in Southern Lao PDR at the Khone Falls.
The Lee traps or Bamboo-wing traps are one of the most popular fi shing gears in Lao PDR, especially in the southern part, yet it has been recently banned since 2017 by a Lao fi shery law.The trap is made by bamboo with eight to 10 meters long and around 1.5 meters wide.The trap is set in appropriate channels and placed in positi on to catch the nocturnal fi sh movement.Moreover, it places directly in the current with half of the bamboo in the water, and another half out of the water.This trap mainly catches fi shes migrati ng upstream when they cannot pass through the strong current and fl ow down into the gear.The locati ons where this trap is set are always owned by certain fi shers, and it is inherited from generati on to generati on.If one wants to use that locati on, he or she has to get permission from the owners through buying or renti ng.
Each year with fi nancial support from the MRC, the LARReC selects about 20 fi shers, who own the Lee traps at Hou Som Yai Channel, for data collecti on including gear informati on, number of individual fi sh caught and species, fi sh weight, and maximum length.Normally, the data are collected from about 20 Lee traps operated at Hou Som Yai Channel during each fi shing season.Yet, the number of the Lee traps can be about 20 in certain years depending on fi sher's ability to build it.
Due to insuffi cient budget, the Lee trap Fishery Monitoring was not implemented during 2014-2016, and in 2017 it was banned by the Lao fi shery law.Hence, data of the Lee trap Fishery Monitoring are available for analysis only from 2008 to 2013.
The Lee trap Fishery Monitoring recorded about 89 fi sh species from 2008 to 2013 (Figure 1).Between this period, it was found that about 72 species under 17 families were caught in 2010, higher than the other years.This corresponds well to the increase in the total fi shing eff ort (i.e.number of acti ve Lee traps daily operated at the Channel) (Figure 1).

Lee Trap Fishery Monitoring in Southern Lao PDR Reveals Fishery Resources Degrada� on from 2008 to 2013
Out of 17, two families from (i) Pangasiidae (Pangasius conchophilus, P. larnaudiei, P. pleurotaenia, and P. siamensis) and (ii) Cyprinidae (Henicorhynchus lobatus and Cirrhinus molitorella) contributed the most to species abundance collected by the Lee traps.
In the same period, the total catch in figure 2 and 3 had a downward trend from 2008 to 2011.It is apparent that the catch of the first three years was higher than that of the last three years.Also, it is noticed that the peak catch was around June and July in each year while the minimum catch was in September because it is close to the end of the fishing season and some traps may be submerged or destroyed by rising flood waters.Although this fishery corresponds well to the wet season, Figure 2 and 3 indicated that the catch might not be correlated with the water level since the trend of the catch went down while that of water level slightly increased.
Like total catch, it was observed that the Catch Per Unit Effort (CPUE) or the catch rate sharply decreased from 4.3 to 2.2 kg per Lee trap per day between 2008 and 2013 (Figure 4).Obviously, the fishery resources were relatively good in 2008, yet this condition turned to be poor as the fishers could not catch fish as much as they used to.
Based on the above-mentioned results, it may be concluded that the fishery resources in southern Lao PDR was degraded in some extent and to prove this statement it is needed to conduct further study as well as a deep analysis using statistical tools to correlate the CPUE/fish abundance with environmental variables (e.g.water flow or water quality).Moreover, it is recommended to maintain the Lee Trap Fishery Monitoring Programme to detect the trend of the fishery resources at that area and importantly the programme may assist the government of Lao PDR in planning its fishery resources management in some ways.Water level in Pakse (m) Total catch (kg)

Figure 1 .
Figure 1.Annually variation in number of species collected by Lee Traps