An investigation into the stranding of Australian sea snakes

Abstract

Strandings of marine animals are a regular occurrence both on Australian and international beaches and provide an opportunity for gathering data on the anatomy, health, and ecology of many oceandwelling species that might be unattainable otherwise. Analysis of stranding data has revealed many important diseases, anthropogenic injuries (primarily as a result of commercial or recreational fishing and boating) and other potential threats in a number of marine species. As such, stranding information is important to include when evaluating the conservation status of marine species whilst developing processes to mitigate declines. Stranding analyses and scientific reports are readily available for a range of marine species, including cetaceans, pinnipeds, dugong and marine turtles, but have not been previously undertaken in sea snakes.True sea snakes (subfamily Hydrophiinae: Hydrophiini) spend their entire life in the marine environment, as opposed to their amphibious counterparts the sea kraits (genus Laticauda). Sea snake species inhabiting Australia's waters are almost exclusively Hydrophiinae, yet are regularly found beach-washed on Australia's coastline, particularly in Queensland. As such, stranded sea snakes in Australia are likely ill or injured individuals. Despite frequent sea snake strandings, demonstrated population declines in some species and recognition that sea snakes are likely to be bio-indicators of the health of the marine ecosystem, an epidemiological investigation of sea snake strandings has not been conducted.The main objective of this thesis was to help address gaps in the literature about sea snake health, disease and stranding events, with particular focus in south east Queensland, where stranding reports occur most frequently. A comprehensive analysis of information from multiple stranding databases was undertaken to assess: (i) species occurrence, (ii) the cause of strandings (where known), (iii) sex predisposition (where identified), (iv) biometrics, (v) stranding locations, and (vi) times of year when strandings occur. This information was from stranding reports, and was collated to provide a comprehensive assessment of reported sea snake stranding events in Queensland, identifying key 'hot-spots' for stranding observations, seasonal occurrence of strandings, and factors that are likely to influence stranding events. Abnormally high numbers of stranded animals were reported in 1996 and 2009 and this appeared to coincide with times of higher than average rainfall, as well as increased onshore winds and wind speed (Chapter 2).To address the paucity of information in the literature about normal clinical health parameters for sea snakes an antemortem assessment guide was developed, detailing procedures for the clinical ii assessment and diagnostic investigation of sea snakes by veterinarians and researchers (Chapter 3).In addition, the first comprehensive set of haematological and biochemical reference ranges for three species of Australian sea snakes were developed from blood collect...

Pinpointing Drivers of Extirpation in Sea Snakes: A Synthesis of Evidence From Ashmore Reef

“…Whilst it is difficult to monitor for mortality events in remote locations such as Ashmore (low observer density but also rapid decomposition and rapid consumption of remains in tropical reef systems), pathogens that drive populations to extinction without direct mortality would be even more difficult to detect. Infections and inflammations caused by endoparasites are a significant cause of stranding in sea snakes along the Queensland coastline in Australia (Gillett, 2017). Disease risk in sea snakes might be higher in males during the breeding season, due to the higher stress levels associated with such activity.…”

“…Disease risk in sea snakes might be higher in males during the breeding season, due to the higher stress levels associated with such activity. Increased levels of testosterone in reptiles can reduce immune reactivity, thus increasing vulnerability to pathogenic organisms (Zapata et al, 1992;Zimmerman et al, 2010;Gillett, 2017). Additional data are required to assess if this is a likely pathway to reduced population health and fecundity in sea snakes at Ashmore and other locations.…”

Future Directions in the Research and Management of Marine Snakes

“…Anecdotal strandings of marine snakes are regularly observed and a few thorough investigations into the state of beach-washed snakes have been conducted (Gillett, 2017). Stranded animals can provide insight into disease, toxicology/bioaccumulation, injury, and the impact of reduced habitat and food reserves.…”

“…Given the variety of people likely to have contact with marine snakes (e.g., offshore oil and gas industry, fishing industry, recreational divers/fishers, beach-goers) and potential hazards (e.g., envenomation), there is an opportunity to collect data and educate the public about this unique group of reptiles. Collection of data from citizen scientists and beach-goers can be as simple as reporting stranded marine snakes (Gillett, 2017), through to more involved structured and repeated sampling by volunteers. A good example of the latter is an ongoing monitoring program in New Caledonia conducted by Goiran colleagues, where citizen-scientist volunteers regularly participate in surveys and submit photographs of marine snakes within fringing reefs in close proximity to recreational beaches.…”