The following is an abstract and some lightly edited text from English et al. (2023) on the Tonle Sap aquatic snake harvest. The paper can be found by clicking here.
The Tonlé Sap Lake is a rich ecosystem, although many of its aquatic species have been depleted by overharvesting. We assessed the quantity and composition of water snakes unintentionally caught during routine fishing practices by examining individuals in the bycatch of a fisherman and sold by a snake trader each day for ten days in Kampong Khleang Commune in November 2019. Each specimen’s length and mass and the occurrence frequency of each species were recorded. Twenty-one fishermen and other villagers were interviewed to investigate further the volume and variety of watersnakes caught as bycatch, methods of capture, timing, and location of breeding and subsequent uses of snakes. Eight species of watersnake were recorded. The most reported and abundant species in our bycatch and trader samples were the Tonlé Sap watersnake Enhydris longicauda (n=763) and the rainbow watersnake E. enhydris (n=209). Interviews revealed that watersnake bycatch was highest at two times of the year which coincided with their breeding seasons. As the Tonlé Sap watersnake is globally Vulnerable and endemic to the lake, we recommend further research into spatial and temporal variation in bycatch and trade, as well as intentional harvesting, to determine if restrictions are warranted to safeguard local watersnake populations, particularly during the breeding season.
Our short study found that E. longicauda was more abundant than E. enhydris in samples from the snake trader and bycatch. The former species accounted for 77% of the trader’s collection and 65% of the bycatch. This differs from previous studies which found E. enhydris was the most common watersnake caught (Stuart et al., 2000; Brooks et al., 2007). Despite earlier studies being more extensive, our results off er a glimpse that suggests three possible scenarios: a decrease in the E. enhydris population which could be related to harvesting for crocodile food or human consumption; an increase in the E. longicauda population; or greater proportions of E. longicauda being caught due to the use of lops rather than gillnets as the main capture method. Further studies comparing temporal and spatial variations and catch techniques are required. The fact that E. longicauda was the most commonly caught species in our study is a cause for concern because the species is endemic to the waters and surrounding wetlands of Tonlé Sap Lake and listed as Vulnerable by the IUCN (Murphy et al., 2010). If these trends continue unabated by any of kind restrictions, the quantities harvested could place major stress on local populations of the species and increase their risk of extinction. Although the average mass of some watersnake species in our study appeared to be lower than previous reports (Table 1), the differences were not statistically significant. Since our sample size was much smaller than Brooks et al. (2009), this may have affected the reliability of our comparison. If future studies with a larger sample size were to show significant differences however, it is possible that over-fishing at the Tonlé Sap Lake could have altered the reproductive ecology of E. enhydris (Murphy et al., 2002). It is necessary to consider that many large, mature, and fecund individuals might be captured and removed from the lake at increased rates, leaving only younger and smaller snakes behind. As such, continuing and expanding our study during the wet season might provide more information on the mass and length of more fully-grown snakes and reduce the number of juveniles collected. Because many of our respondents indicated that the lop was the primary tool used for fi shing—a generalized trap traditionally used to catch fish which does not specifically target snakes—this could have implications for any future attempts to regulate the capture of watersnakes (Deap et al., 2003). Additionally, people on the lake may use an alternative means of catching snakes we did not learn about, such as illegal fishing equipment.
Moreover, using the lop may have skewed our results toward the types and sizes of watersnakes caught. Although some of our respondents claimed they only caught fish and never bought or sold watersnakes, all of them could distinguish the different species and often provided their Khmer names. Even people who claimed to have limited interactions with watersnakes recognized and named at least some of the species displayed in photographs. Additionally, the species most respondents identified as common matched those most often found in the samples we examined from the individual fisherman and trader.
Citation
English, M., Winters, K., Lasater, M., Dainty, M., Meyerhoff , M. & Wagner, P. (2022) A dry season glimpse of watersnake bycatch and trade from the flooded forests of Kampong Khleang, Tonlé Sap Lake. Cambodian Journal of Natural History, 2022, 38–46.
