The effectiveness of rehabilitation post catastrophic environmental events as a conservation strategy for marine turtles

Abstract

School of Veterinary Science 2In-water monitoring of the health and well-being of marine vertebrates is usually expensive and therefore may not be undertaken by management agencies with financial constraints.However, the use of stranding data can provide a cost-effective alternative estimation of disease and mortality. Strandings for marine turtles in Queensland are recorded in a web based database (StrandNet) managed by the Queensland Government's Department of Environment and Heritage Protection (EHP). Data recorded in StrandNet for marine turtles stranded from the entire east coast of Queensland between 1996 and 2013 were investigated for patterns of stranding in an attempt to identify which factors, such as extreme weather events, may cause stranding of marine turtle species and, further, use these patterns to predict stranding and the required responses to mitigate the negative impact mass mortalities have on endangered species such as marine turtles.Significant stranding trends in Queensland between 1996-2013 were: (i) an increase in the number of animals reported stranded within the study site; (ii) a species (loggerhead and green marine turtles) prevalence for stranding; (iii) a seasonal effect on different age classes stranding with most overall strandings occurring between August and November; and (iv) stranding hotspots (Moreton Bay, Hervey Bay, Rockhampton region and Cleveland Bay) persisting throughout the study timeframe.One strategy to mitigate the negative effects of marine turtle stranding is to provide medical care to those that strand alive in the hopes they can return to the functional population. Rehabilitation of marine turtles in Queensland is multifaceted. It treats individual animals, serves to educate the public, and contributes to conservation. Of 13854 marine turtles reported as stranded during the 18-year period of investigation, 5022 of these turtles stranded alive with the remainder verified as dead or of unknown condition. A total of 2970 (59%) of these live strandings were transported to a rehabilitation facility.The original cause of stranding has an impact on the success of rehabilitation and this may influence where treatment efforts are directed. For example, of the turtles admitted to rehabilitation exhibiting signs of disease (natural cause of illness) (18% of all animals admitted to rehabilitation), 88% of them died either unassisted or by euthanasia. Sixty-six percent of turtles admitted for unknown causes of stranding died either unassisted or by 3 euthanasia. By contrast, all turtles recorded as having a buoyancy disorder with no other presenting problem or disorder recorded, were released alive.One hundred and one of the turtles released from rehabilitation were reencountered: 77 reported as restrandings (20 dead, 13 alive subsequently died, 11 alive subsequently euthanized, 33 alive) and 24 recaptured during normal marine turtle population monitoring or fishing activities. Considering the high mortality rate and low successful recapture rate, rehabilitation may not be...