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Van Dijk, P. P. , Impacts of non-harvest anthropogenic activities on freshwater turtles in the united states. Unpublished paper presented at USFWS Workshop on Conservation and Trade Management of Freshwater and Terrestrial Turtles in the United States. 
Added by: Sarina Wunderlich (06 Jul 2014 16:17:27 UTC)
Resource type: Conference Paper
BibTeX citation key: anon2010.16571
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Categories: General
Keywords: Chrysemys picta, Emydidae, Habitat - habitat, Nordamerika - North America, Schildkröten - turtles + tortoises
Creators: Van Dijk
Collection: USFWS Workshop on Conservation and Trade Management of Freshwater and Terrestrial Turtles in the United States
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Abstract     
Many Freshwater Turtle populations and species are threatened to varying degrees by a wide variety of threats. This presentation aims to provide a summary introduction to the spectrum of general, habitat-wide and turtle-specific threats impacting turtles, and introduce the underlying biological factors determining why turtle populations are generally more intensively affected by population impacts than traditionally harvested and managed species, like deer, quail, fish and shellfish, are. Habitat impact on freshwater turtles range from wetland drainage, structural alteration to riverine systems by dams and reservoirs as well as sandmining, the direct and indirect effects of water pollution (industrial, municipal and surface runoff), and deforestation and other impacts on the dry-land areas used by freshwater turtle species as part of their lifecycle. Invasive plant and animal species can alter critical habitat features to make an area less suitable for turtle populations to inhabit, but alternatively can also provide new or additional sources of food and shelter to turtles. The impact of habitat loss is easily explained as ‘No suitable habitat, then no surviving turtle population’. Impacts specific to freshwater turtles include human collection of turtles at various life stages and for a variety of purposes, including as pets and other recreational functions such as turtle racing, as well as subsistence consumption, domestic and export trade for consumption and medicinal purposes. Accidental mortality when turtles cross roads or reside in agricultural lands has been documented to be of great significance as road networks fragment remaining habitats and riparian buffer zones along rivers and wetlands are often much smaller than individual turtles’ activity ranges. Accidental mortality rates of freshwater turtles in commercial, recreational or scientific fisheries activities are significant for certain species and localities, particularly for the Diamondback Terrapin in the Blue Crab fishery, but also wanton destruction of turtles which take fishermen’s bait as perceived competitors or fish predators. The impact of introduced invasive species, or subsidized native species, on turtle populations is only partly documented, but ranges from increased, sometimes overwhelming, nest predation rates to increased mortality of adult turtles. Correspondingly, the possible introduction of non-native turtle species into US waters (such as the widely traded Chinese Softshell Turtle) and moving native species into different parts of the country (such as the release of traded pet turtles into local environments) carry the risk of introducing diseases, upsetting ecological balances, and genetic pollution of resident native turtle populations. Epidemic diseases hve not been documented conclusively in North American freshwater turtles, but the prevalence of Herpes- and Ranavirus in Terrapene box turtles and the impact of disease on the Flattened Musk Turtle indicate that this is at least a potential threat. Turtles as a group are characterized by life history attributes that include late maturity (generally at between 5 and 20 years of age), longevity and long-term annual reproduction, high mortality of eggs and small juveniles, and high annual survivorship of subadult and adult animals. In contrast to ‘traditional’ managed wildlife and fisheries species, where the effects of offtake levels and management measures become measurable within years, the time scale of turtle life history results in exploitation and recovery effort effects becoming apparent, and continuing to have effects, for decades after the events occur. This has obvious implications for long-term turtle population management, and documents why traditional management measures as commonly applied for game birds, fish or shellfish do not apply to turtles.
Added by: Sarina Wunderlich  
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