The light sticks used in longline fisheries resemble the disposable plastic tubes popular with children on Halloween. The steady glow draws fish, which then find baited hooks and are caught on the lines. The lights also seem to fascinate turtles, however, which are equally likely to chomp on fish bait, or get snagged in the hooks and lines.
“Juvenile turtles are indiscriminant eaters and bite nearly everything small that they encounter,” said Ken Lohmann, UNC-Chapel Hill professor of biology and senior author of the study. “Under natural conditions, most small objects floating or swimming through the sea are potential sources of food. But nowadays, with fishing lines, plastic, and garbage in the ocean, biting everything is not such a great strategy.”
The study appears in the May 2007 issue of the journal Animal Conservation. John Wang, a former graduate student at Carolina and now a research associate with the Joint Institute for Marine and Atmospheric Research at the University of Hawaii, was the lead author of the study. Grants from the National Oceanic & Atmospheric Administration (NOAA) and the National Science Foundation provided funding.
The new findings may help fisheries decrease the number of turtles caught on lines, the researchers said. Most longlines deploy their hooks below the depths where turtles usually swim, so shading the lights to direct illumination downward instead of upward might make the lights harder for turtles to see. Similarly, switching to colors that turtles can’t detect very well might also reduce turtle deaths.
All sea turtles are endangered species. A recent estimate published in the journal Ecology Letters suggests 200,000 loggerhead and 50,000 leatherback turtles may die each year in commercial fishery longlines. Total populations have declined in the past 20 years, Lohmann said.
While it’s difficult to separate the impact of longline fisheries from other threats turtles face, researchers say that the loss to longlines is significant because the turtles caught are often adolescents, which die before they have a chance to reproduce. Only about one in 5,000 turtles ever survive to adulthood. In the past, those lucky enough to last a few years in the ocean could expect a long life and would replenish the population. With the advent of longline fishing, the number of survivors has dwindled. “A lot of turtles that beat the odds and would otherwise have lived long lives are now being caught on longlines,” Lohmann said.
Lohmann, Wang and their team tested loggerhead turtle’s response to light sticks in a large, water-filled tank. Turtles were placed into a soft cloth harness and tethered to an electronic tracking device that monitored their movements. Safely encased in the soft fabric and released in the tank, the turtles swam as if in the open ocean, apparently unaware that they aren’t going anywhere, Wang said.
When glowing light sticks were introduced to the tank, the turtles swam toward them, as if curious about the lights, Lohmann said. The color or type of the light stick did not seem to matter. The turtles paddled toward green, blue and yellow light sticks, as well as toward both plastic chemical lightsticks and newer models based on reusable LEDs.
Both captive-raised and wild-caught juvenile turtles were attracted to glowing light sticks, whether in total darkness or underneath a night sky, Wang said. When the lights weren’t activated, they were unappealing. The experiments were conducted at the National Marine Fisheries Services’ Galveston Laboratory in Texas and at a turtle nesting area in south Florida.
The study needs to be repeated with longlines in the open sea to confirm that light sticks attract turtles under natural conditions in the ocean, Lohmann said. The researchers are also curious to check leatherback turtles for a similar response.
Becky Oskin | EurekAlert!
A new indicator for marine ecosystem changes: the diatom/dinoflagellate index
21.08.2017 | Leibniz-Institut für Ostseeforschung Warnemünde
Value from wastewater
16.08.2017 | Hochschule Landshut
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
23.08.2017 | Life Sciences
23.08.2017 | Life Sciences
23.08.2017 | Physics and Astronomy