It’s A Cruel, Cruel World:It’s A Cruel, Cruel World:Anthropogenic Threats to Anthropogenic Threats to

Sea TurtlesSea Turtles

By Katie HartBy Katie Hart

Anthropogenic ThreatsAnthropogenic Threats

Effects, processes or materials caused by Effects, processes or materials caused by human activityhuman activity

Why are sea turtles vulnerable?Why are sea turtles vulnerable? Leatherbacks in the Pacific have declined Leatherbacks in the Pacific have declined

more than 95% in the last 25 years and more than 95% in the last 25 years and Pacific loggerheads have undergone at Pacific loggerheads have undergone at least an 80% decline in nesting females least an 80% decline in nesting females over the last 20 years (Lewison over the last 20 years (Lewison et alet al., ., 2007)2007)

Beach RenourishmentBeach Renourishment

Temporary fix for an Temporary fix for an eroding beacheroding beach

Eroded beaches are a Eroded beaches are a serious problem for serious problem for nesting sea turtles nesting sea turtles

Renourished beaches Renourished beaches may be less suitable may be less suitable for turtle nesting than for turtle nesting than

natural beachesnatural beacheshttp://www.billandjennyswygert.com/EdistoBeachRenourishment.htm

Artificial LightArtificial Light

Hatchlings look for flatter, Hatchlings look for flatter, brighter locationsbrighter locations

Artificial lights can cause Artificial lights can cause misorientation or misorientation or disorientationdisorientation

www.awesomebeachvacations.com/myrtlebaywatch.htm http://www.nt.gov.au/nreta/parks/management/masterplan/links/index.html

Marine DebrisMarine Debris

Plastics do not Plastics do not biodegradebiodegrade

Plastics concentrate Plastics concentrate DDT, PCBs, and other DDT, PCBs, and other oily pollutants oily pollutants

Plastic bags can be Plastic bags can be mistaken for jellyfishmistaken for jellyfish

http://www.pritchettcartoons.com/images/plastic.gif

http://www.vanaqua.org/aquanew/uploads/debris_noaa_sm.jpg

Floating Marine Debris SightingsFloating Marine Debris Sightings

Barnes, D. K. A. and P. Milner. 2005. Marine Biology

Heavy MetalsHeavy Metals

Anthropogenic emissions have tripled the concentrations Anthropogenic emissions have tripled the concentrations of Mercury (Hg) in the atmosphere and in the surface of Mercury (Hg) in the atmosphere and in the surface ocean ocean

Green turtles are thought to be mostly herbivorous, and Green turtles are thought to be mostly herbivorous, and loggerhead turtles are carnivorous. Loggerhead turtles loggerhead turtles are carnivorous. Loggerhead turtles had higher concentrations of metalshad higher concentrations of metals

Godley, et al. 1999. Mar. Poll. Bull.

Drift Gillnet BycatchDrift Gillnet Bycatch Targets the swordfish and thresher Targets the swordfish and thresher

shark in Californiashark in California Season/Area closures from Aug. 15 to Season/Area closures from Aug. 15 to

Nov. 15 each year since 2001 to Nov. 15 each year since 2001 to protect leatherback turtles protect leatherback turtles

http://www.mxsocal.org/newsitems/towimage/Drift-Net.gif Carretta, et al. 2004. Mar. Fish. Rev.

Pelagic Longline BycatchPelagic Longline Bycatch Longlines dangle thousands of individually baited Longlines dangle thousands of individually baited

hookshooks Turtles try to swallow bait or become entangled in Turtles try to swallow bait or become entangled in

geargear

http://www.afma.gov.au/information/students/methods/pelagic.htm

Lewison, et al. 2004. Ecology Letters

Responsible for one third of Responsible for one third of all fisheries bycatchall fisheries bycatch

http://www.afma.gov.au/information/students/methods/demersal_tr.htm

Prawn Trawl BycatchPrawn Trawl Bycatch

Brewer, et al. 2006. Fisheries Research

Ghost FishingGhost Fishing

Matsuoka, et al. 2005. Fisheries Science

Literature CitedLiterature Cited Barnes, D.K.A. and P. Milner. 2005. Drifting plastic and its consequences Barnes, D.K.A. and P. Milner. 2005. Drifting plastic and its consequences

for sessile organism dispersal in the Atlantic Ocean. Marine Biology. for sessile organism dispersal in the Atlantic Ocean. Marine Biology. 146:815-825. 146:815-825.

Brewer, D., D. Heales, D. Milton, Q. Dell, G. Fry, B. Venables and P. Jones. Brewer, D., D. Heales, D. Milton, Q. Dell, G. Fry, B. Venables and P. Jones. 2006. The impact of turtle excluder devices and bycatch reduction devices 2006. The impact of turtle excluder devices and bycatch reduction devices on diverse tropical marine communities in Australia's northern prawn trawl on diverse tropical marine communities in Australia's northern prawn trawl fishery. Fisheries Research. 81:176-188. fishery. Fisheries Research. 81:176-188.

Carretta, J.V., T. Price, D. Peterson and R. Read. 2004. Estimates of Carretta, J.V., T. Price, D. Peterson and R. Read. 2004. Estimates of marine mammal, sea turtle, and seabird mortality in the California drift gillnet marine mammal, sea turtle, and seabird mortality in the California drift gillnet fishery for swordfish and thresher shark, 1996-2002. Marine Fisheries fishery for swordfish and thresher shark, 1996-2002. Marine Fisheries Review. 66:21-30. Review. 66:21-30.

Godley, B.J., D.R. Thompson and R.W. Furness. 1999. Do heavy metal Godley, B.J., D.R. Thompson and R.W. Furness. 1999. Do heavy metal concentrations pose a threat to marine turtles from the Mediterranean Sea? concentrations pose a threat to marine turtles from the Mediterranean Sea? Marine Pollution Bulletin. 38:497-502. Marine Pollution Bulletin. 38:497-502.

Lewison, R.L. and L.B. Crowder. 2007. Putting longline bycatch of sea Lewison, R.L. and L.B. Crowder. 2007. Putting longline bycatch of sea turtles into perspective. Conservation Biology. 21:79-86. turtles into perspective. Conservation Biology. 21:79-86.

Lewison, R.L., S.A. Freeman and L.B. Crowder. 2004. Quantifying the Lewison, R.L., S.A. Freeman and L.B. Crowder. 2004. Quantifying the effects of fisheries on threatened species: the impact of pelagic longlines on effects of fisheries on threatened species: the impact of pelagic longlines on loggerhead and leatherback sea turtles. Ecology Letters. 7:221-231.loggerhead and leatherback sea turtles. Ecology Letters. 7:221-231.

Matsuoka, T., T. Nakashima and N. Nagasawa. 2005. A review of ghost Matsuoka, T., T. Nakashima and N. Nagasawa. 2005. A review of ghost fishing: scientific approaches to evaluation and solutions. Fisheries Science. fishing: scientific approaches to evaluation and solutions. Fisheries Science. 71:691-702. 71:691-702.