Many Dry Tortugas Loggerheads Actually Bahamas Residents plus 1 more

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Title: USGS Newsroom

Many Dry Tortugas Loggerheads Actually Bahamas Residents plus 1 more

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Many Dry Tortugas Loggerheads Actually Bahamas Residents

Posted: 16 Apr 2015 07:05 AM PDT

Summary: Many loggerhead sea turtles that nest in Dry Tortugas National Park head to rich feeding sites in the Bahamas after nesting, a discovery that may help those working to protect this threatened species

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New Information May Help Protect Threatened Turtle

Contact Information:

Kristen Hart ( Phone: 954-236-1067 ); Gabrielle Bodin ( Phone: 337-266-8655 );

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GAINESVILLE, Fla.—Many loggerhead sea turtles that nest in Dry Tortugas National Park head to rich feeding sites in the Bahamas after nesting, a discovery that may help those working to protect this threatened species. 

Researchers from the U.S. Geological Survey used satellites to track the population of loggerheads that nest in the Dry Tortugas – the smallest subpopulation of loggerheads in the northwest Atlantic – and found the turtles actually spend a considerable portion of their lives in the Bahamas, returning to the Dry Tortugas to nest every two-to-five years. They then spend three-to-four months nesting in the Dry Tortugas before returning to the Bahamas.

This new information will help resource managers better identify areas to target for conservation efforts.

“Collaborative conservation efforts focused on protecting important loggerhead residence and foraging areas between the United States and Bahamas could offer significant protection for the Dry Tortugas loggerheads,” said USGS Research Ecologist Kristen Hart, lead author of the study. “Two other subpopulations of loggerheads that nest in Northern and Peninsular Florida and also travel to residence areas in the Bahamas would benefit from this protection as well.”

The current estimate of the subpopulation of loggerheads that nest in the Dry Tortugas hovers between 258–496 females. Populations of the turtle are difficult to estimate. Loggerheads start nesting when they are approximately 25 years old, and then nest every two-to-five years until they die. Researchers have found that marking females that return to the same beach to nest every two-to-five years is the most practical way to get an indication of population size.

The northwest Atlantic population of loggerhead turtles is listed as “threatened” under the Endangered Species Act, which provides them protection from intentional harm or harvest and protects their most important habitats within the United States and its waters.

In this study, researchers tracked marked turtles over six nesting seasons. Results showed the turtles selected almost the exact same residence area in the Bahamas during their second tracking event. In addition, tracking data showed that individual residence areas generally did not overlap, leading the scientists to believe that loggerheads at this foraging ground may establish territories.

Turtles tagged in more than one Dry Tortugas nesting season showed similar migration paths and timing as compared to their own previous migrations. Their migratory paths included the Florida Strait, a major shipping fairway where ship strikes could threaten the turtles.

After traveling through non-protected waters from the Dry Tortugas, the turtles primarily selected residence areas in non-protected zones once reaching the Bahamas. Although direct turtle harvest has been illegal in the Bahamas since 2009, commercial fishing has the potential to impact the loggerheads’ food resources and poses a direct threat to them as they can become entangled in lines attached to gear.

Loggerhead sea turtles are primarily carnivorous and feed mostly on shellfish that live on the bottom of the ocean, such as horseshoe crabs, clams, mussels, and other invertebrates. Their powerful jaw muscles help them to easily crush the shellfish. Once reaching sexual maturity, the turtles nest every two-to-five years, depositing two-to-six clutches of 75 to 120 eggs approximately every two weeks during the nesting season. After nesting, they migrate back to their foraging site.

The Northwest Atlantic loggerhead nesting numbers declined sharply in the 1990s followed by an increase over the last six years making it difficult to assess the trend at this point. Scientists remain concerned about the ongoing threats to this population which include loss or degradation of nesting habitat from coastal development and beach armoring; disorientation of hatchlings by beachfront lighting; nest predation by native and non-native predators; degradation of foraging habitat; marine pollution and debris; watercraft strikes; disease; and incidental take from channel dredging and commercial trawling, longline and gill net fisheries. 

Future studies to characterize the resources within residence areas and individual loggerhead behaviors at their residence areas will also help to guide conservation efforts.

The study, “Bahamas connection: residence areas selected by breeding female loggerheads tagged in Dry Tortugas National Park, USA,” by Kristen M. Hart, USGS; Autumn R. Sartain, a contractor with the USGS; and Ikuko Fujisaki, University of Florida, is available online.

Genetics Provides New Clues about Lionfish Invasion

Posted: 16 Apr 2015 07:00 AM PDT

Summary: New genetic data suggest the red lionfish invasion in the Caribbean Basin and Western Atlantic started in multiple locations, not just one as previously believed, according to a new study led by the U.S. Geological Survey

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Contact Information:

Margaret Hunter ( Phone: 352-264-3484 ); Christian Quintero ( Phone: 813-352-3487 );

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GAINESVILLE, Fla.— New genetic data suggest the red lionfish invasion in the Caribbean Basin and Western Atlantic started in multiple locations, not just one as previously believed, according to a new study led by the U.S. Geological Survey.

Florida has often been cited as the likely location of the introduction, but the new research suggests multiple introductions occurred, with some potentially coming from the more southern parts of the range. The Caribbean Basin stretches from parts of Florida’s Gulf Coast through South America.

Genetically unraveling the progression of the red lionfish invasion and determining if introductions are still occurring could help guide response and control efforts for this and other invasive fishes. The spiny fish is well known as a predatory invasive species that negatively impacts its non-native environment, disrupting marine food webs as they prey in coral reef ecosystems on invertebrates and fish, including game fish juveniles, such as snappers and groupers. Lionfish are native to the Indo-Pacific region, and were likely brought to the United States via the pet trade.  

USGS researchers analyzed red lionfish samples from fourteen countries and territories in the Greater Caribbean and Western Atlantic in an effort to better understand the invasive species’ population structure and dispersal patterns. While red lionfish can be found in the Gulf, this study did not include any samples from that region. 

 “The red lionfish can be used to help up understand other non-native populations and their invasion dynamics,” said USGS geneticist Margaret Hunter. “The more we know about this species and its progression, the more we can help resource managers and others fighting the invasion be prepared to help control lionfish colonization in new locations. Ultimately, any information gleaned from this species could be applied to managing and assisting with eliminating future invasive species.”

Researchers found that unique regional genetic patterns separated the studied area into northern and southern regions, with the split occurring near the Bahamas. Given the regional genetic differences revealed in this study, the researchers now suspect multiple introductions. One rare genetic strain was found in only a few samples in the southern region, but was pervasive in the north.

“Studying the genetic strains across regions gives us insight into how these fish are spreading. Dispersal against the flow of ocean currents may explain why we see this rare strain in the south, but even if that is the case, additional support for multiple introductions exists; the genetic patterns found in this study support the idea of multiple introductions, and could be due to additional releases in the south,” said John Butterfield, a USGS contract biologist and lead author of the publication.

Continued releases would increase the potential for more genetically diverse red lionfish to join the current population, which could counter future removal efforts or allow them to more rapidly expand their range beyond current boundaries.

The broad dispersal of red lionfish may in part be due to their reproductive habits. Females can spawn up to once every four days, which could result in one female releasing up to two million eggs a year. Following spawning, larvae can disperse long distances via ocean currents, for up to 35 days.

In the United States, federal and state agencies are working together to help combat this invasive fish through the Aquatic Nuisance Species Task Force. This intergovernmental entity has drafted a National Invasive Lionfish Prevention and Management Plan that is in the final stages of approval. The main goals of the plan are to prevent the spread of invasive lionfish; coordinate early detection and rapid response efforts; control and management of the current invasive population; and fully assess the impact that the invasion is having on native species and habitats.

The full study is available online. More information on USGS Southeast Ecological Science Center’s genetics work is available at its genetics website, or on its genetic research fact sheet.