An Introduction to the Sea Turtles of Virginia. Amber Knowles CBNERR-VA July 22, 2008

Transcription

1 An Introduction to the Sea Turtles of Virginia Amber Knowles CBNERR-VA July 22, 2008

2 Overview Introduction to species of sea turtles Focus on Loggerhead and Kemp s ridley sea turtles Importance of the Chesapeake Bay VIMS Sea Turtle Stranding and Research Program

3 General Facts Marine animals that spend almost entire life in aquatic environment Exception to this is nesting Most are characterized by hard shell and flipper like limbs adapted to marine environment Unable to tuck neck and limbs in to shell like other species of turtles Like other turtles breathe air Can stay below surface for long periods of time

4 Sea Turtles Species 7 species of sea turtles in worlds ocean Loggerhead Kemp s Ridley Leatherback Green Olive Ridley Hawksbill Flatback 6 of the species are found in US waters with exception of Flatback which is found only in Australian waters

5 Sea Turtles Found in Chesapeake Bay 5 of the 7 species of sea turtles are present or have been documented in the Chesapeake Bay Loggerhead and Kemp s Ridley are most abundant Green and leatherback also present Only 2 Hawksbills have been documented in Virginia waters

6 Why the Chesapeake Bay? Juveniles use Chesapeake as benthic foraging habitat Feed mainly on horseshoe and blue crabs Migrate to Chesapeake Bay when food available in pelagic habitats can no longer support them

7 Life Cycle

8 Migration in to Chesapeake Bay Move in to the bay May to June as temperatures rise above 18 Celsius, leave the bay October to November as temperatures fall below 20 Celsius Between 2500 and 5500 sea turtles in bay annually Down significantly from numbers of sea turtles estimated to be in bay in early 1980s and 1990s

9 Distribution within Chesapeake Bay

10 Loggerhead

11 Loggerhead Sea Turtle Most numerous turtle in bay Named for it s large head Listed as threatened under Endangered Species Act In Virginia Waters range in size from 25 to 35 inches and can weigh upwards of 200 lbs Exhibit high site fidelity while in Virginia waters Tend to spend large amounts of time in same locations

12 Loggerhead Sea Turtle Few nests found annually near Back Bay National Wildlife Refuge area each year (most northerly nesting area) Nesting is possible on Virginia s Eastern Shore as well Diet : horseshoe crabs, blue crabs, knobbed and channeled whelk Masters student Erin Seney did diet analysis research from 2000 to 2003, found change in diet from crustacean to more finfish

13 Kemp s Ridley

14 Kemp s Ridley Sea Turtle Most endangered sea turtle and one of the most endangered animals in world Second most abundant sea turtle in Virginia waters Smallest turtle found in Chesapeake Bay, most specimens are dinner plate sized Average weight of around 30 pounds Prefer more shallow water habitats than Loggerheads

15 Kemp s Ridley Follow similar seasonal migrations to and from Chesapeake Bay as Loggerheads Their diet is mostly benthic molluscs and crustaceans Nest in what are called arribadas on small stretch of beach in Rancho Nuevo, Mexico 1942 there is a film with 40,000 nesting females visiting beach in one day

16 Green sea turtle Hawksbill Leatherback

17 Fun Facts about Virginia s Other Sea Turtles Green sea turtle gets its name because their fat is green Largest source of turtle meat Leatherbacks Unlike other marine turtles do not have scutes on carapace. Instead back is comprised of longitudinal ridges with leathery covering. Deepest diving and largest migrations seen among all sea turtles Hawksbill What you see sold as tortoise shell Named for beaklike mouth

18 Endangered Species Act and Sea Turtles All sea turtles except Flatback protected under Endangered Species Act Loggerhead threatened, others found in Virginia all listed as endangered Threats to species Habitat destruction Marine pollution Overfishing Fishery interactions Research being done to help conserve the different species of sea turtles

19 Research at VIMS Stranding Program Tagging Mark-Recapture Tracking Aerial Surveys Nesting Surveys

20 VIMS Sea Turtle Stranding Program Purpose of the program is to monitor population trends Started in 1979 when Dr. Jack Musick arrived at VIMS All data collected is reported to National Marine Fisheries Service and United States Fish and Wildlife Service

21 What is a stranding? Live or dead turtle found on land or floating in water Animals should not be approached by public Must have permit to handle animals

22 Sea Turtle Strandings in Virginia 250 to 350 turtle strand annually Most of these animals are juvenile Loggerheads and Kemp s ridleys Stranding peak in May/June and in smaller peak in October Cause of death is often very hard to determine

23 Data Collected During Stranding Location of stranding Morphometric data (measurements) Condition of animal (live, dead, decomposition, etc) External anomalies Tag information Necropsies are performed when able on dead animals

24 Dead Sea Turtle Strandings Trying to answer question of why did animal strand and collect any data that might help answer that question Necropsies are performed whenever possible Any abnormalities are noted

25 Live Sea Turtle Strandings If healthy animals are tagged and released If sick or injured animals are treated, tagged, and released Virginia Aquarium and Marine Science Center is where most sea turtles need rehabilitation in Virginia waters go for treatment

26 Sea Turtle Tagging Flipper (Inconel tags) PIT (Passive Integrated Responder) Satellite and Radio Tags

27 Inconel Flipper Tags

28 Mark Recapture Studies All Inconel flipper tags used on East Coast are obtained from Archie Carr Center for Sea Turtle Research Keep database of when and where animals are tagged and then keep track of future contact VIMS has own tagging database with recapture data

29 PIT (Passive Integrated Responder) It is a radio frequency device that transmits a unique individual code to a reader where it is displayed in a numeric or alphanumeric form (ex: FF3423A5) Inserted with syringe in to fleshy part of flipper Stays with animals longer than Inconel tags Tagging

30 Satellite and Radio Tags Radio Tag Satellite Tag

31 Sea Turtle Tracking Satellite Track long term sea turtle migration patterns Radio Look at short term movements and surfacing patterns Sonic Give better directional information, often used with radio tagging

32 Aerial Surveys Aerial surveys are used to estimate sea turtle abundance Researches board small over-wing planes and count sea turtles observed in randomly assigned transects

33 Aerial Survey Transects in Chesapeake Bay Chesapeake Bay was divided in to Upper Bay (blue lines) and Lower Bay (purple/grey lines) 8 transects flown once a week from May to September/October

34 Nesting Surveys Virginia hosts small number of sea turtle nests each year at Back Bay National Wildlife Refuge Back Bay National Wildlife Refuge

35 Nesting Surveys Beach checked for evidence of sea turtle nesting activity VIMS researchers collected data from nesting females and tagged with Inconel and satellite tags Movements post-nesting were monitored Nests themselves were monitored by staff at Back Bay National Wildlife Refuge

36 THANK YOU!

37 QUESTIONS?