The proposed project will address Goal 14 of the Sustainable Development Goals calling to conserve marine resources. The conservative life-history (slow growth, late reproduction, low fecundity) of marine mammals make them vulnerable to anthropogenic threats that reduce their survivability. As top predators, dolphins maintain balanced and productive ecosystems providing food security and livelihoods to local people (Teh et al., 2014). Irrawaddy dolphin (Orcaella brevirostris), Indo-Pacific humpback dolphin (Sousa chinensis) and Indo-Pacific finless porpoise (Neophocaena phocaenoides) are distributed across nearshore coastal waters of Southeast Asia. The species’ coastal distribution expose them to anthropogenic threats including fisheries bycatch, habitat degradation and climate change affecting coastal water flows and turbidity. Irrawaddy dolphins can be found in Cambodia’s four coastal provinces (Beasley and Davidson 2007; Tubbs et al. 2020), while Indo-Pacific humpback dolphins and Indo-Pacific finless porpoise have only been confirmed in Koh Kong and Sihanoukville provinces (Smith et al. 2016). In Kep province, Irrawaddy dolphins are present year-round, with the area classed as an Important Marine Mammal Area (IUCN-MMPATF 2020). The IUCN Red List classifies these species as Endangered, Vulnerable and Vulnerable, respectively, all with declining population trends (https://iucn-csg.org/). The species are protected in Cambodia although lack sufficient data for regional assessments and conservation actions (MAFF 2007).
Dolphin spatial distribution and abundance can be investigated using observational and image data (for individual identification of dolphins) collected during boat-based surveys and processed using capture-recapture methods (Sharpe and Berggren 2019). All dolphins and porpoises produce echolocation signals to navigate and to detect prey. Passive acoustic monitoring (PAM) using deployed recorders (e.g. F/C-PODs, chelonia.co.uk) can be used to investigate species occurrence and foraging occurrence at high temporal resolution (Yang et al. 2020). Therefore, combining visual and acoustic data collection allow for comprehensive assessment of species occurrence, distribution, abundance and behaviour.
Questionnaire based methods with local fishers can be used to investigate fisheries effort and catch/bycatch of species in areas lacking detailed information (Moore et al. 2010). Resulting catch rates together with statistics on total fishing effort can be used to estimate total species catch and where catch rates may need mitigation.
This project will provide the necessary data for regional and national, and contribute to global, evidence-based status assessments for each species to inform management strategies. An interdisciplinary approach combining natural and social science techniques will be applied to provide data on spatial and temporal occurrence, abundance and fisheries mortality.
Objective 1: Investigate Irrawaddy dolphin, Indo-Pacific humpback dolphin and Indo-Pacific finless porpoise spatial and temporal occurrence, and abundance in the Koh Kong, Sihanoukville, Kampot and Kep provinces, Cambodia (Fig. 1) using boat based surveys and passive acoustic monitoring (PAM).
Objective 2: Use PAM techniques to record species specific clicks during boat surveys. Apply statistical techniques to produce algorithms that allow classifying clicks to species. Apply the developed algorithms to data from PAM deployments to investigate temporal patterns of each species occurrence.
Objective 3: Design and use a questionnaire to investigate fisheries effort and dolphin bycatch rates in Cambodia’s four coastal provinces (Koh Kong, Sihanoukville, Kampot, Kep). Combine collected data with official fisheries statistics to estimate total mortality for each species and province.
Objective 4: Use the information from Objectives 1-3 to conduct evidence-based status assessments for each species to inform conservation and management strategies.
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Figure 1 showing the study area in Cambodia including the four coastal provinces (Koh Kong, Sihanoukville, Kampot and Kep) where proposed research project will be conducted.