Marine turtles in Cambodia 167
declining marine resources, increasing poverty and rising market demand for turtle products (Pich, 2002). According to fishers, push and trawl nets (operated by
large vessels) are associated typically with high marine tur- tle bycatch in Cambodia, a finding that echoes the wider literature (Gilman et al., 2010). Push and trawl nets are simi- lar in terms of fishing locations and predominantly used to target shrimp. Push nets aremoved along the seabed in shal- low coastal waters (,20mdeep) through eithermanual op- eration or by machine, whereas trawl nets are cone-shaped nets that are towed by one or two boats along the seabed or in midwater. Both of these types of gear are used frequently in waters ,20 m deep along the Cambodian coast, in contravention of the Fisheries Law, and also around islands, thus posing a significant risk to turtle foraging grounds. The literature on the impacts of push nets on marine turtles is sparse; however, seabed-contacting fishing gear has been identified as leading to a greater probability of bycatch and mortality than surface-set gear (Tiwari et al., 2013). Moreover, trawl nets are recognized as a global threat tomar- ine turtles, and consequently they have become the focus of bycatch reduction efforts since the 1980s, when researchers recognized that Gulf of Mexico shrimp fisheries were driving high marine turtle mortality in the USA (WWF, 2017). Ray hooks, the other fishing technique associated widely
with marine turtle bycatch in Cambodia, are a longline gear with J-shaped hooks. The lines can be up to 10 km in length, with 5,000–6,000 hooks on one longline. They are often used in shallow waters for catching rays and other fish, particularly in seagrass beds and mangroves, which are also favoured foraging grounds of green turtles. Indus- trial longlining is cited widely as a high turtle bycatch risk, and we suggest that the risk remains significant even in relatively small-scale longline fisheries such as those in Cambodia (Tiwari et al., 2013). The relative numbers of marine turtle species reported in
bycatch corroborate findings from earlier consultations, with hawksbill and green turtles being the most common- ly sighted species, whereas olive ridley, loggerhead and leatherback turtles are rare and possibly locally extinct (Fauna & Flora International, 2011). The only published record for the latter species occurred c. 2 decades ago (Stuart et al., 2002). The high levels of reported bycatch for green and hawksbill turtles during 2016–2018 demon- strate the continued threat to these species. However, with- out recent nesting records or fisheries-independent data on turtle populations the ability to draw any quantitative inferences regarding current turtle populations is limited.
Recommendations
Under theCambodian Fisheries Law, trawling inwater,20m in depth and/or inside designated Marine Protected Areas is banned. Despite this, illegal fishing activities occur
frequently, having been documented extensively by marine protected area monitoring led by Fauna & Flora and the Fisheries Administration. Therefore, stronger fisher engage- ment to improve compliance with this key regulation is crit- ical, especially as Cambodia’s marine protected area network expands and encompasses key areas of turtle habi- tat. If the use of trawl and push nets continues in shallow waters, key foraging habitats such as seagrass and coral reefs will be degraded and incidents of turtle bycatch will continue, with illegal fishing by national and foreign vessels still a key threat to the remaining Cambodian turtles (Riskas et al., 2018). In addition, even if compliance incentives for the Fisheries Law increase, it could be argued that the 20m law is impossible for fishers to comply with in practice, as many Cambodian fishing vessels lack depth-sounding technology. Therefore, gear-based or spatial measures could be easier to comply with and implement. In addition, increased compliance with the Endangered Species Sub- decree 123, which prohibits the consumption and trade of marine turtle products, is also required, with evidence sug- gesting continued localized demand for turtle meat and the presence of shell products in localmarkets (Sour et al., 2021). A further key policy recommendation is to promote the implementation of the National Plan of Action for Marine Turtles (2016–2026), which is beyond the mid-point of its working period (Vong et al., 2018). The plan includes key objectives that respond to the threats identified in this study, including reducing anthropogenic threats that cause mortality of marine turtles and the destruction of their eggs, and protecting and rehabilitating marine turtle foraging and nesting grounds. Trials of fishing gear modification or replacement tech-
niques have been recommended for Cambodian fisheries, using measures that mitigate the bycatch of marine turtles (McNamara, 2016; Swimmer et al., 2017). For example, ray hook longlines with J-shaped hooks (a commonly used gear in Cambodia) could be replaced by circle hooks, which have been demonstrated to reduce turtle bycatch and mortality in longline fisheries (e.g. in the Eastern Pacific context; Andraka et al., 2013). However, this would require pilot trials and consultations to assess the efficacy of such hooks in Cambodia, quantify any negative impacts on fishers and secure government buy-in for scaling up bycatch mitigation. Another gear-focused intervention would be the trial of turtle excluder devices, particularly for commercial fishers using trawl nets. Although there is evidence demonstrating the efficacy of turtle excluder devices for reducing turtle bycatch, significant barriers remain to the effective implementation of such devices in Cambodia, including the absence of government legislation mandating or subsidizing their use, and the challenge of incentivizing fishers to participate (Prakash et al., 2016). Long-term monitoring of impacts should be conducted not only for bycatch but also for coastal development and
Oryx, 2023, 57(2), 160–170 © Fauna & Flora International, 2023. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605322000862
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