SEA TURTLES Of Delaware Bay - Amazon S3 · SEA TURTLES Of Delaware Bay James R. Spotila Pamela Plotkin John Keinath. The Magnificent Seven Green Turtle Herbivore-eats sea grasses

SEA TURTLESOf Delaware Bay

James R. SpotilaPamela PlotkinJohn Keinath

The Magnificent Seven

Green Turtle

Herbivore-eats sea grasses and algae

Hawksbill

Spongivore

Loggerhead

A carnivore

Olive Ridley A carnivore

Kemp’s Ridley

A carnivore

Flatback

A carnivore

Only in Australia

Leatherback

Jelly-vore

Loggerhead

Kemp’s Ridley

Delaware Bay and Sea Turtles

• Juvenile sea turtles in Bay June- October• Rich source of crabs and other invertebrates• Genetic studies

– loggerheads along northeastern states nest in Mexico, Florida, Georgia and South Carolina

• Satellite Telemetry– Wassaw Island Georgia to mouth of Delaware

Bay

Methods• Aerial Surveys June- August 1997

– Cessna 172• 100-224 mph• 300-500 ft above sea level

• In-Water Captures June- September 1997– Tangle nets

• 100 yd x 8 ft x 10 in mesh• 100 yd x 30 ft x 6 in mesh• Large bullet surface floats• Retrieved every 30 minutes• 25 ft Parker boat

• Sea Turtle Sighting Survey– Public users

Aerial SurveysFour transect linesTwo observersOne data recorder (+ pilot)Strip transect 300 m wideJune- August 1997

Locations of turtlesSpeciesTime

Strip transect estimates of density (Epperly et al 1995)

Sea Turtle Sighting Survey

• Posters• Return post cards• Locations in New Jersey

and Delaware

Close up of Response Card

Aerial Surveys

• June – 10 loggerheads• July – 9 loggerheads• August- 14 loggerheads

• Density- 21-33 turtles/100 km2

Red dots- JuneYellow dots- JulyBlue dots- August

Red dots- JuneYellow dots- JulyBlue dots- August

Turtles were found near shipping channelQuestion- What happens in fall and winter?

In Water Captures

• 2 nets on 21 days• 103 hours• Observed 10 loggerheads (2 juveniles)• Captured 2 live male loggerheads

– 90 and 108.2 cm• Found ½ of dead loggerhead floating in

water

Public Sea Turtle Sightings• 60 postcard responses

– Most were recreational fishermen from lower Bay– A few sightings from Cape May- Lewes Ferry

• 65 turtles• 57 loggerheads• 4 hawksbills- probably small loggerheads or

Kemp’s Ridleys- spit out bait and hissed• 2 green turtles- probably loggerheads • 2 not identified to species• 12 of 65 turtles were caught by fishermen- 18.5%

Sea Turtle DensityLocation Density (turtles/100 km2)

• Delaware Bay- 21-33 • Lower Chesapeake Bay- 0-57 • Mid Chesapeake Bay- 0-8.5• Pamlico Sound- 0-6.5 • Core Sound- 0-30• Southern Georgia- 0-62

Conclusions1. Density of turtles is comparable or greater than in southeastern US2. Lower Delaware Bay provides important habitat for loggerheads3. Significant numbers of sea turtles are incidentally hooked

by recreational fishermen4. Many turtles swim in and around the shipping channel5.Collision with boats and propellers may be a threat to turtles6.Benthic trawling may be a significant threat to sea turtles in the Bay7.Decline of horseshoe crabs threatens the food supply for these turtles.

There is a serious need for more data about sea turtles in Delaware Bay if we are to reduce human impacts on these species