Impacts of dams on freshwater turtles: a global review to identify conservation solutions

Dams create many impacts on freshwater ecosystems and biodiversity. Freshwater turtles are at direct and indirect risk due to changes caused by damming including the loss of terrestrial and aquatic nesting and feeding habitats, changes to resource availability and reduced dispersal. We reviewed the global scientific literature that evaluated the impact of dams on freshwater turtles, and carried out additional searches of literature published in seventeen languages for studies evaluating actions to mitigate the impact of dams. The search produced 43 published articles documenting dam impacts on 29 freshwater turtle species from seven families (Chelidae, Chelydridae, Emydidae, Geoemydidae, Kinosternidae, Podocnemididae and Trionychidae) in 13 countries. More than a third of studies (41.9%, n = 18) focused on nine North American species of the Emydidae. Few studies were found from Europe and Asia and none from Africa. The number of studies, life-history stage studied and threat status differed significantly between temperate and tropical latitudes. Most studies were from temperate latitudes, where studies focused more on adults and less threatened species compared with tropical latitudes. Studies evaluated dam impacts as barriers and changes to water flow and quality, but no studies were found that assessed turtles and changes to land cover or mercury caused by dams. More than half of the studies (59%, n = 24) suggested actions to help mitigate dam impacts. Yet, only four studies on three temperate and one tropical species documented the effect of interventions (dam removal, flow management, artificial pond maintenance and community-based action). These findings demonstrate a lack of documented evidence evaluating dam impacts on freshwater turtles particularly in tropical regions. This lack of evidence reinforces the importance of strengthening and maintaining robust long-term studies of freshwater turtles needed to develop effective conservation actions for this group of vertebrates.

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Prospects for freshwater turtle population recovery are catalysed by pan-Amazonian community-based management

10.7287/peerj.preprints.27044v1 ◽

2018 ◽

Author(s):

Darren Norris ◽

Carlos A Peres ◽

Fernanda MIchalski ◽

James P Gibbs

Keyword(s):

Sustainable Use ◽

Freshwater Turtle ◽

Tropical Species ◽

Area Network ◽

Freshwater Turtles ◽

Community Based ◽

Tropical Regions ◽

Continental Scale ◽

Turtle Population ◽

Business As Usual

Sustainable use as a mechanism for the conservation and recovery of exploited wildlife populations remains intensely debated, including for freshwater turtles, a diverse and imperilled group of aquatic reptiles that are an important food source for many residents of tropical regions. Here we evaluated the geographical extent of recovery options for a heavily exploited tropical freshwater turtle fauna across 8.86 M km2 of South American river catchments under Business-as-Usual (BAU), Protection (Pr) and Community-Based-Management (CBM) scenarios. For the widespread indicator species, Podocnemis unifilis, demographic analysis showed that populations subject moderate levels of female harvest (≤10%) can recover over broad areas if concurrent headstarting of hatchlings is practiced more widely. With regional strengthening of the protected area network unlikely, CBM developed with harvest frameworks derived from demographic rates appropriate to tropical species could catalyse a rapid continental scale recovery of Amazonian freshwater turtles within a few decades.

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Prospects for freshwater turtle population recovery are catalysed by pan-Amazonian community-based management

10.7287/peerj.preprints.27044 ◽

2018 ◽

Author(s):

Darren Norris ◽

Carlos A Peres ◽

Fernanda MIchalski ◽

James P Gibbs

Keyword(s):

Sustainable Use ◽

Freshwater Turtle ◽

Tropical Species ◽

Area Network ◽

Freshwater Turtles ◽

Community Based ◽

Tropical Regions ◽

Continental Scale ◽

Turtle Population ◽

Business As Usual

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Plastic ingestion by freshwater turtles: a review and call to action

Scientific Reports ◽

10.1038/s41598-021-84846-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Adam G. Clause ◽

Aaron J. Celestian ◽

Gregory B. Pauly

Keyword(s):

Marine Species ◽

Marine Turtle ◽

Freshwater Turtle ◽

Freshwater Turtles ◽

Plastic Pollution ◽

Potential Threat ◽

Implementation Quality ◽

Turtle Species ◽

Marine Turtles ◽

Conservation Concern

AbstractPlastic pollution, and especially plastic ingestion by animals, is a serious global issue. This problem is well documented in marine systems, but it is relatively understudied in freshwater systems. For turtles, it is unknown how plastic ingestion compares between marine and non-marine species. We review the relevant turtle dietary literature, and find that plastic ingestion is reported for all 7 marine turtle species, but only 5 of 352 non-marine turtle species. In the last 10 years, despite marine turtles representing just 2% of all turtle species, almost 50% of relevant turtle dietary studies involved only marine turtles. These results suggest that the potential threat of plastic ingestion is poorly studied in non-marine turtles. We also examine plastic ingestion frequency in a freshwater turtle population, finding that 7.7% of 65 turtles had ingested plastic. However, plastic-resembling organic material would have inflated our frequency results up to 40% higher were it not for verification using Raman spectroscopy. Additionally, we showcase how non-native turtles can be used as a proxy for understanding the potential for plastic ingestion by co-occurring native turtles of conservation concern. We conclude with recommendations for how scientists studying non-marine turtles can improve the implementation, quality, and discoverability of plastic ingestion research.

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The influence of a new water infrastructure development on the relative abundance of two Australian freshwater turtle species

Australian Journal of Zoology ◽

10.1071/zo17082 ◽

2018 ◽

Vol 66 (1) ◽

pp. 57 ◽

Cited By ~ 1

Author(s):

Natalie J. Clark ◽

Courtenay E. Mills ◽

Nicolette A. Osborne ◽

Kerry M. Neil

Keyword(s):

Relative Abundance ◽

Temporal Variability ◽

Monitoring Program ◽

Freshwater Turtle ◽

Spatial And Temporal Variability ◽

Main Body ◽

Water Infrastructure ◽

Turtle Species ◽

Australian Freshwater ◽

The Impact

Development of water infrastructure benefits water security and agriculture but poses risks to habitat and aquatic fauna. Wyaralong Dam was constructed on Teviot Brook in 2010 to provide future urban water supplies for South East Queensland, Australia. Construction of the dam created a large impoundment area and environmental impact assessment predicted significant impacts upon resident freshwater turtle species and their habitats. Differences in habitat requirements, life-history characteristics and sensitivity to change between the Macquarie River turtle (Emydura macquarii macquarii) and the common saw-shelled turtle (Myuchelys latisternum) were expected to influence the impact of the dam on the spatial and temporal abundance of these species. The relative abundance of each species was monitored at sites located within, upstream and downstream of the impoundment across wet and dry seasons during the dam’s first five years of operation. The results of this monitoring program indicate that spatial and temporal variability in the relative abundance of E. macquarii macquarii and M. latisternum occurred during the study but not all expected impacts were realised. Contrary to expectation, the relative abundance of E. macquarii macquarii did not increase over time within, upstream or downstream of the dam. M. latisternum showed greater temporal variability at some sites; however, no clear relationship between relative abundance and operational years was observed during the monitoring program. Spatial variability in relative abundance between sites was dependent upon season, with trends generally consistent across both turtle species. Where differences between species were observed, these are suspected to have resulted from the influence of environmental conditions on species-specific movement behaviours. The monitoring program confirmed the use of the upper limits of the impoundment and the plunge pool below the dam wall by both turtle species but relative abundance within the main body of the impoundment remained low throughout monitoring. The results of the study allow for consideration of the suitability of predefined management measures and the development of recommendations for future monitoring programs prescribed for water infrastructure developments.

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Population status and distribution of freshwater turtles in Taiwan

Oryx ◽

10.1017/s0030605310000013 ◽

2010 ◽

Vol 44 (2) ◽

pp. 261-266 ◽

Cited By ~ 9

Author(s):

Tien-Hsi Chen ◽

Kuang-Yang Lue

Keyword(s):

Native Species ◽

Mainland China ◽

Iucn Red List ◽

Freshwater Turtle ◽

Freshwater Turtles ◽

Chinese Market ◽

Negative Effects ◽

Turtle Species ◽

Mauremys Mutica ◽

Effective Conservation

AbstractBecause of burgeoning demand in the Chinese market and extensive habitat loss more than half of the freshwater turtle and tortoise species in Asia are categorized as Endangered or Critically Endangered on the IUCN Red List. To investigate the distribution and status of the native freshwater turtle species of Taiwan a trapping programme was conducted during 2001–2007, yielding a total of 1,828 individuals of four native species at 103 sites. Mauremys sinensis was the most abundant and widely distributed species; it was collected from 70 sites and accounted for 78.6% of all turtles captures. Mauremys mutica comprised 17.8% at 46 sites. Pelodiscus sinensis were captured in low numbers at 19 sites. No Mauremys reevesii were collected on the main island of Taiwan but the species was found on Kinmen Island near mainland China. Capture success was low at most sites and overall sex ratios were significantly male-biased in all species, suggesting that the freshwater turtles have suffered from the negative effects of habitat disturbance and extensive exploitation. Effective conservation measures are urgently required to ensure the viability of the native freshwater turtle species of Taiwan.

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An Examination of Limiting Factors of Chrysemys picta bellii (Western painted turtles) in the Lower Willamette River Basin, Oregon

10.15760/mem.74 ◽

2021 ◽

Author(s):

◽

James Holley ◽

Keyword(s):

River Basin ◽

Chrysemys Picta ◽

Limiting Factors ◽

Freshwater Turtle ◽

Willamette River ◽

Turtle Species ◽

Chrysemys Picta Bellii ◽

Nesting Activity ◽

Willamette River Basin ◽

The Impact

Oregon’s two native freshwater turtle species, Chrysemys picta bellii (Western painted turtle) and Actinemys marmorata (Northwestern pond turtle), have seen significantly reduced population sizes since the founding of Portland in 1845, with estimates of up to 90% for A. marmorata. This project examined turtle nesting activity at 25 sites across a range of turtle populations and habitats around the Lower Willamette River Basin. All discovered turtle nesting activity was found in areas of high solar exposure. We found 93% of over 400 nest attempts to have been depredated across the 25 sites, well above most other reported rates. At several sites, many aborted nest attempts were found atop gravel roadbeds, indicating that lack of appropriate substrate is potentially limiting nesting success. The presence of greater than five pedestrians per hour at turtle nesting areas was correlated with a substantial decrease in nesting attempts suggesting that management of recreational activities may play a role in the amount of nesting activity occurring. Hence, site-specific solutions, such as importing substrate, alteration of path locations or seasonal trail closures to lessen human foot traffic disturbance of turtle nesting attempts, are likely to improve recruitment rates of native turtles in the Lower Willamette Basin. Further studies that improve knowledge of population demographics, the impact of human activities on turtles, and habitat needs of juvenile turtles are needed to support long-term self-sustaining turtle populations.

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Body temperature of free-living freshwater turtles, Hydromedusa maximiliani (Testudines, Chelidae)

Amphibia-Reptilia ◽

10.1163/156853806778189990 ◽

2006 ◽

Vol 27 (3) ◽

pp. 464-468 ◽

Cited By ~ 6

Author(s):

Fernando Martins ◽

Franco Souza

Keyword(s):

Body Temperature ◽

Water Temperature ◽

Stream Water ◽

Life Stage ◽

Freshwater Turtle ◽

Freshwater Turtles ◽

Body Temperatures ◽

Turtle Species ◽

Mountainous Regions ◽

Main Factor

AbstractField body temperatures of the Maximilian's snake-necked turtle, Hydromedusa maximiliani, a small freshwater turtle species endemic to Atlantic rainforest mountainous regions in Brazil, were studied. Turtle body temperatures and water temperatures were significantly related, but turtle body temperature averaged 1°C higher than stream water temperature, this difference being statistically significant. A multivariate model revealed that only water temperature was significantly related to turtle body temperature while body size had no effect. There was no effect of sex and life stage on turtle body temperature, implying that water temperature was the main factor determining body temperatures. Thermoconformity was verified for all sampled individuals. The broad implications of these results are also discussed.

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Muddy waters: the influence of high suspended-sediment concentration on the diving behaviour of a bimodally respiring freshwater turtle from north-eastern Australia

Marine and Freshwater Research ◽

10.1071/mf14117 ◽

2016 ◽

Vol 67 (4) ◽

pp. 505 ◽

Cited By ~ 1

Author(s):

Jason R. Schaffer ◽

Mark Hamann ◽

Richard Rowe ◽

Damien W. Burrows

Keyword(s):

Low Temperature ◽

Suspended Sediment ◽

Sediment Concentration ◽

Dive Duration ◽

Diving Behaviour ◽

Freshwater Turtle ◽

Freshwater Turtles ◽

Aquatic Respiration ◽

Eastern Australia ◽

The Impact

Increased suspended-sediment concentrations (SS) in rivers can affect aquatic respiration in riverine fauna by impairing respiratory function. Bimodally respiring freshwater turtles are likely to be sensitive to changes in SS because increased concentrations may affect their ability to aquatically respire. However, the impact of SS on the diving behaviour of bimodally respiring freshwater turtles has not been formally investigated. To test this, we examined the influence of dissolved oxygen (DO) saturation (25%, 100%) and temperature (17°C, 25°C) on the diving behaviour of Elseya irwini under clear (0mgL–1) and turbid (79mgL–1) conditions. We hypothesised that low temperature and high DO % saturation would increase dive duration and that high SS would negate the effect of DO, decreasing dive duration under highly oxygenated conditions. Our data demonstrated that increased SS significantly reduced mean dive duration by 73% (97.4±10.1min in 0mgL–1 trials v. 26.4±3.2min in 79mgL–1 trials) under conditions of low temperature (17°C) and high DO % saturation (100%) only. Increased SS directly affects the utilisation of DO by this species, so as to extend submergence times (aquatic respiration) under optimal conditions, raising concerns about the effect of SS on the persistence of populations of physiologically specialised freshwater turtles.

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Illegal trade and conservation requirements of freshwater turtles in Nanmao, Hainan Province, China

Oryx ◽

10.1017/s0030605306000949 ◽

2006 ◽

Vol 40 (3) ◽

pp. 331-336 ◽

Cited By ~ 17

Author(s):

Gong Shiping ◽

Wang Jichao ◽

Shi Haitao ◽

Song Riheng ◽

Xu Rumei

Keyword(s):

Conservation Status ◽

Habitat Destruction ◽

Conservation Strategies ◽

Freshwater Turtle ◽

Hainan Province ◽

Illegal Trade ◽

Freshwater Turtles ◽

Illegal Activities ◽

Almost All ◽

The Impact

China has one of the world's most diverse freshwater turtle faunas but is also a major consumer of freshwater turtles. In the 1980s over-collecting, illegal trade and habitat destruction increased dramatically, pushing almost all Chinese turtles towards extinction. Despite the critical status of Chinese turtles little has been done to quantify and evaluate the impact of illegal activities on wild populations. We used a combination of market surveys and questionnaires to examine the illegal trade and conservation status of native freshwater turtles in Nanmao, Hainan Province, from February to August 2003. We found a total of 245 collected freshwater turtles comprising eight species. These data indicate that Nanmao has a rich freshwater turtle fauna that is being affected heavily by illegal poaching. No effective measures have been taken to protect the few remaining wild turtle populations. The main factors that lead to illegal trade include the cultural belief that turtles are a viable food/medicine product, lack of conservation awareness, poaching of turtles as a supplement to income, and poor law enforcement. Possible conservation strategies are discussed.

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Preliminary data on an affordable UAV system to survey for freshwater turtles: advantages and disadvantages of low-cost drones

Journal of Unmanned Vehicle Systems ◽

10.1139/juvs-2018-0037 ◽

2020 ◽

pp. 1-8

Author(s):

Javier E. Canahuati Escobar ◽

Mark Rollins ◽

Shem Unger

Keyword(s):

Image Quality ◽

Preliminary Data ◽

Low Cost ◽

Freshwater Ecosystems ◽

Freshwater Turtle ◽

Freshwater Turtles ◽

Advantages And Disadvantages ◽

Terrestrial Environments ◽

Baseline Information ◽

Flight Parameters

Unmanned aerial vehicles (UAVs) are established, valuable tools for wildlife surveys in marine and terrestrial environments; however, they are seldom utilized in freshwater ecosystems. Therefore, baseline data on the use of UAVs in lotic environments are needed that balances flight parameters (e.g., altitude and noise level) with image quality, while minimizing disturbance to individuals. Moreover, the traditional high-cost UAVs may present challenges to researchers conducting rapid assessments on species presence with limited funding. However, emerging, affordable UAV systems can provide this preliminary data to researchers, albeit with caveats on reliability of data. We tested a low-cost UAV system to document freshwater turtle presence, species distribution, and habitat use in a small North Carolina wetland. We observed minimal instances of turtles fleeing basking sites (∼0.7%), as this UAV system was only ∼2.1 dB above ambient noise levels at an altitude of 20 m. Freshwater turtles were found primarily in algal mat basking habitats with highly variable numbers observed across locations and flights, likely due to image quality reliability and altitude. Our affordable UAV system was successful in providing baseline information on species presence, size distribution, and habitat preference of turtles in freshwater ecosystems.

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