Tag Archives: marine biology


42,000 Turtles legally killed each year

Over 42,000 turtles are legally killed each year, 80% of them endangered green turtles (Chelonia mydas), a study suggests.

British scientists investigated which countries allowed turtles to be killed, and how many of each species died, the Diversity and Distributions Journal reported.

Ten countries account for more than 90% of the catch, with Papua New Guinea, Nicaragua and Australia taking almost three-quarters between them. Legal take of turtles is comparable to estimates of by-catch.

Widespread commercial catch of turtles has contributed significantly to their decline.

The first place to protect turtles was Bermuda, as early as 1620. Although 42,000 seems an enormous number now, in the 60s Mexico alone was catching over 380,000 a year. The IUCN Red List of threatened species has listed marine turtles since 1982, giving them protection from the 198 countries now signed up to the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).

The IUCN writes that “Perhaps the most detrimental human threats to green turtles are the intentional harvests of eggs and adults from nesting beaches and juveniles and adults from foraging grounds.“. Other threats include bycatch in marine fisheries, habitat degradation at nesting beaches and feeding areas, and disease.

As well as 37,339 green turtles, an estimated 3456 hawksbill turtles, 1051 loggerhead turtles, 263 olive ridley and 62 leatherback turtles are captured.

Further Reading:
Humber, F., Godley, B. J., Broderick, A. C. (2014), So excellent a fishe: a global overview of legal marine turtle fisheries. Diversity and Distributions. doi: 10.1111/ddi.12183

Underwater Street View -Bermuda, North East Breaker

Google adds more Virtual Dives to Underwater Street View

With the help of the Catlin Seaview Survey, Google has added more underwater locations to its “Street View“.

Google put the first marine images up in September 2012, with dives in Australia, the Philippines and Hawaii. Now it covers 16 more countries, including the Galapagos, Monaco, Bermuda and Mexico. It really is a fantastic way to gauge potential dive sites before visiting a country. And it isn’t just for fun. The seaview survey will make ocean change plainly visible for all to see.

For shallow reef surveying – from 0 to 30 m – marine biologists use cameras attached to underwater scooters. Three 360o cameras take pictures from different angles to produce a panoramic seascape. For each image captured, a geo-location and camera direction is also recorded, meaning it’s possible to retake the photograph at a later date from the exact same camera position as the original.

Underwater camera used to make Google Underwater Street View
Mapping the Ocean Floor

Marine creatures like manta rays and turtles apparently find it particularly fascinating. The Catlin Seaview team often catch them checking out their own reflection in the wide-angle camera-lens-housing ports.

An underwater tablet has been developed especially for the project, which can connect to the internet and communicate live with the world from underwater.

For dives deeper than 30 m, the survey team sends down under underwater robots. They use data loggers to track changes in water temperature and light level.

The new locations you can now view on Google include Cozumel’s Santa Rosa Wall and Columbia Deep; Monaco’s Larvotto Marine Reserve and Roche Saint Nicholas (featuring the Oceanographic Museum of Monaco); the Cancun Underwater Museum and whale sharks at Isla Contoy in Mexico

Emily’s Pinnacles, Bermuda

Further Reading
Google Underwater Street View
Catlin Seaview Survey
Catlin Global Reef Record

Southern Right Whale

Whale Watching from Space

But not by astronauts or space tourists. Scientists from the British Antarctic Survey are using satellite images to detect and count southern right whales (Eubalaena australis).

In recent years there have been over 420 deaths of these whales in their nursery grounds at Península Valdés in Argentina. (Out of a population last estimated at 2577 whales.) Most of the dead were calves. This number of deaths suggests that the right whale population, and its ecosystem, may be less healthy and robust than previously thought. The whales at Península Valdés comprise the largest single population and the high mortality rate has raised fresh concern for the future of the species.

Traditionally whale population size has been assessed by counting from boats, planes or shore. This is labour-intensive, costly and can be inefficient. Detection probabilities are high for ship surveys, but where surveys are carried out by small airplanes rates can be down to 40%. The researchers have tested a method of identifying whales automatically from high resolutions satellite images. They chose southern right whales to evaluate their method, as, they say “The southern right whale is an ideal subject for this work for many of the same reasons as it was an ideal whale to hunt, specifically its large size and a tendency, in the breeding season, to bask near the surface in large aggregations around sheltered coastal waters.”

The researchers – Peter T. Fretwell, Iain J. Staniland and Jaume Forcada – analysed the images manually and using image processing software.

Probable whales found by automated

Probable whales found by the automated analysis. Several of the images could be interpreted as whale pairs, or as a mother and calf, others may be displaying behaviour such as tail slapping, rolling or blowing. On several images there is a strong return at one end of the feature which is mostly likely the calluses on the whales head. Reprinted under a CC BY license with permission from British Antarctic Survey and DigitalGlobe.

Manually identified whales were put into three classes; shapes that are whale-like and whale-sized are classed as probable whales, other objects are classed as possible whales, but may include bubble slicks and some groups of seabirds. The third class are objects interpreted as sub-surface feature that are potentially whales. Their automated method found 89% of the objects manually classed as probable whales, with 23.7% false positives.

How do they know a whale-like blob is a whale? They used three criteria used to identify any objects in remotely sensed imagery:

  1. The object is the right size and shape to be a whale
  2. The object is in a place we would expect to find whales
  3. There are no (or few) other types of objects that could be misclassified as whales to cause errors of commission.

Overall the researchers were satisfied with their results and suggested that larger surveys over whole calving areas, which could potentially measure thousands of square kilometres, could be automated with a degree of success using their techniques.

Southern right whales were hunted extensively from the 17th through to the 20th century. The pre-whaling population has been estimated at 55,000–70,000 dropping to a low of just 300 animals by the 1920s.

Further Reading:
Fretwell PT, Staniland IJ, Forcada J (2014) Whales from Space: Counting Southern Right Whales by Satellite. PLoS ONE 9(2): e88655. doi:10.1371/journal.pone.0088655

Photo credit: Southern right whale (Peninsula Valdés, Patagonia, Argentina) by Michaël Catanzariti

Cuttlefish and Camouflage

Cuttlefish – Master of Camouflage

What makes the Cuttlefish so good at controlling its colour and blending in with its surroundings? This month scientists at Harvard University and the Woods Hole Marine Biological Laboratory have helped answer that question.

It has been long known that the skin of the Cuttlefish contains chromatophores: yellow, red, and brown pigmented sacs that the Cuttlefish can expand and contract to allow their skin to act as a color filter of their surrounding light. In addition, Cuttlefish contain leucophores and iridophores that, respectively, scatter light over the entire visible spectrum and reflect light.

Eye of the cuttlefish

Under control of their nervous system, Cuttlefish can reportedly change the surface area of the pigmented sacs by as much as 500% (allowing for different combinations of pigments to be combined to a greater or lesser degree and providing different gradations in color filtration). However, that alone doesn’t explain the color repertoire of the Cuttlefish and the speed with which it can change colors.
What the scientists discovered and published for the first time is that the chromatophores also contain luminescent protein structures that allow them to actively emit light, not just reflect and filter the ambient light from their environment.

In addition, they also discovered the presence of reflectin in the chromatophores, a high-refractive-index protein that, they suggest, allows the chromatophores, when highly stretched out, to more effectively absorb light than if they contained color pigments alone. Another protein, crystallin, was also found there, adding to the understanding that chromatophores are not simply sacs of pigment as previously thought.

It is this combination of light emission and enhanced reflection/filtering abilities that provides the Cuttlefish with its impressive flexibility of appearance.
The researchers suggest that bioinspiration from the Cuttlefish could provide designs for new types of thin, flexible displays with superior color contrast and accuracy. They also note that this enhanced color contrast would provide better ability to disrupt pattern recognition as compared with pixilation camouflage technologies (such as are found in current military uniforms).

Further Reading
The original published article is entitled The structure–function relationships of a natural nanoscale photonic device in cuttlefish chromatophores and the publication can be found here: http://rsif.royalsocietypublishing.org/content/11/93/20130942

The abstract is free, but the article requires a subscription. This article from Harvard School of Engineering and Applied Sciences gives a high level summary of the article with some discussion of potentially interesting applications.

The Cuttlefish: a Source of Inspiration gives a more general overview of this fascinating creature.

Photo credits: Tim Nicholson, David Collins

Jill Studholme

By Jill Studholme. Jill edits SCUBA News (ISSN 1476-8011), the monthly newsletter with articles on diving and marine science.She tweets as @SCUBANews. You can find her on Google+ at https://plus.google.com/+JillStudholme/.


Extinction Threatens Quarter of Sharks and Rays

A quarter of sharks, rays and chimaeras are threatened with extinction, according to a new study by the International Union for Conservation of Nature. Large, shallow-water species are at most risk.

The group found that only 23 percent of these fish is listed as “least concern” on the IUCN Red List of Threatened Species. Of the 1,041 known species, 25 are listed as critically endangered, 43 are endangered, and 113 are vulnerable to extinction. This is the worst reported status for any major vertebrate group except for amphibians.

“Our analysis shows that sharks and their relatives are facing an alarmingly elevated risk of extinction,” says Dr Nick Dulvy, IUCN Shark Specialist Group Co-Chair and Canada Research Chair at Simon Fraser University in British Columbia. “In greatest peril are the largest species of rays and sharks, especially those living in shallow water that is accessible to fisheries.”

The most threatened families are:

  1. Sawfishes (Pristidae)
  2. Angel sharks (Squatinidae)
  3. Wedgefishes (Rhynchobatidae)
  4. Sleeper rays (Narkidae)
  5. Whiptail stingrays (Dasyatidae)
  6. Guitarfishes (Rhinobatidae)
  7. Thresher sharks (Alopiidae)

Overfishing is the main threat to the species, according to the paper. Reported catches of sharks, rays and chimaeras peaked in 2003 and have been dominated by rays for the last 40 years. Actual catches are likely to be grossly under-reported.

Unintentionally caught sharks and rays account for much of the catch, yet developing markets and depleting fishery targets have made this “bycatch” increasingly welcome. Intentional killing of sharks and rays due to the perceived risk that they pose to people, fishing gear or target species is contributing to the threatened status of at least 12 species.

Sharks and their relatives include some of the latest maturing and slowest reproducing of all vertebrates, exhibiting the longest gestation periods and some of the highest levels of maternal investment in the animal kingdom. This makes them very sensitive to over-fishing.

The Indo-Pacific, particularly the Gulf of Thailand, and the Mediterranean Sea are the two ‘hotspots’ where the depletion of sharks and rays is most dramatic. The Red Sea is also home to a relatively high number of threatened sharks and rays, according to the experts.

The report was published in the journal eLIFE.

Photo credit: Sawfish by Forrest Samuels (CC BY-NC-SA 2.0).

Further Reading:
eLife 2014;3:e00590

Shark feed - Tiger Shark

Shark Feeding Dives change Relative Abundances of Sharks

Feeding sharks for the benefit of divers is becoming more and more common, but is controversial. New research suggests that feeding in areas with several different sharks, over time, leads to one species increasing in numbers at the expense of the others. Published in PLOS ONE(1), the study looked at the Shark Reef Marine Reserve feeding site in Fiji from 2003 to 2012.

Eight species of shark regularly visited the site in 2003: bull shark (Carcharhinus leucas), grey reef shark (Carcharhinus amblyrhynchos), whitetip reef shark (Triaenodon obesus), blacktip reef shark (Carcharhinus melanopterus), tawny nurse shark (Nebrius ferrugineus), silvertip shark (Carcharhinus albimarginatus), sicklefin lemon shark (Negaprion acutidens), and tiger shark (Galeocerdo cuvier). By 2012, there were more individual sharks visiting, but fewer species. The winner was the bull shark. The smaller tawny nurse shark, silvertip shark and sicklefin lemon shark became very rare visitors.

The larger sharks get more of the food, and so the rewards for the smaller sharks become less. If they are not getting much food from the dives, there is less incentive for the smaller sharks to keep visiting.

Economically, sharks provide much more money through tourism than could be earned by killing and eating them. The pacific island of Palau, for example, receives 8% of its gross domestic product from shark diving.(2)

In spite of the obvious benefit of feeding rather than killing sharks, scientists and conservationists have also highlighted drawbacks. One study indicated that sharks become more aggressive to each other – perhaps because there are so many of them in a small area – and to other species – which might lead to people being bitten more frequently.(3)

When the shark-feeding dives are linked to marine protection projects, then they can contribute to shark conservation. Even better if the shark dive operators also team up with scientists to monitor shark population size and behaviour.

Photo credit: Terri Goss (CC BY 2.5)

Journal References
(1)Brunnschweiler JM, Abrantes KG, Barnett A (2014) Long-Term Changes in Species Composition and Relative Abundances of Sharks at a Provisioning Site. PLoS ONE 9(1): e86682. doi:10.1371/journal.pone.0086682

(2)G.M.S. Vianna, M.G. Meekan, D.J. Pannell, S.P. Marsh, J.J. Meeuwig (2012) Socio-economic value and community benefits from shark-diving tourism in Palau: A sustainable use of reef shark populations. Biological Conservation 145 267–277

(3)Clua E, Buray N, Legendre P, Mourier J, Planes S (2010) Behavioural response of sicklefin lemon sharks Negaprion acutidens to underwater feeding for ecotourism purposes. Mar Ecol Prog Ser 414:257-266


Great White Sharks Live more than 70 Years

Great whites (Carcharodon carcharias) may live far longer than previously thought, according to a new study that used bomb radiocarbon dating to determine age.

Sharks are typically aged rather like counting tree rings, by counting growth band pairs deposited in their vertebrae. However, sharks grow more slowly as they get older and the band pairs become too thin to read. Age is then underestimated.

A new study by researchers at NOAA’s Northeast Fisheries Science Center (NEFSC) and the Woods Hole Oceanographic Institution used bomb radiocarbon dating on eight sharks caught between 1967 and 2010 in the Northwest Atlantic Ocean. This technique uses the discrete radiocarbon pulse in the environment caused by the detonation of nuclear bombs in the 1950s and 1960s as a “time stamp”. Radiocarbon levels incorporated into the band pairs are measured and related to a reference chronology to determine the absolute age of a fish.

Of the eight sharks studied, the oldest was found to be 73 when it died. In all previous studies of shark lifespan, no shark was estimated to be over 23 years old.

White sharks are considered vulnerable under the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. Although the Great White Shark is such a famous species of fish, very little is known about its biology. Its maximum size remains a matter of debate. Some estimate around 6 m and others 6.4 m or more. Lengths and ages at maturity for both sexes remain undetermined. A mature female of 500 cm was estimated to have reached around 14 to 16 years, but that was when the oldest individual reported was a female assumed to be not much more than 23. The real age at maturity may be much older.

The study hints at possible sexual dimorphism in growth rates, and raises concerns that white shark populations are considerably more sensitive to human-induced mortality than previously thought.

With lifespan estimates of 70 years and more, white sharks may be among the longest-lived fishes. Sharks that mature late, have long life spans and produce small litters have the lowest population growth rates and the longest generation times. Increased age at maturity would make white sharks more sensitive to fishing pressure than previously thought, given the longer time needed to rebuild white shark populations.

Further Reading
Hamady LL, Natanson LJ, Skomal GB, Thorrold SR (2014) Vertebral Bomb Radiocarbon Suggests Extreme Longevity in White Sharks. PLoS ONE 9(1): e84006. doi:10.1371/journal.pone.0084006
Fergusson, I., Compagno, L.J.V. & Marks, M. 2009. Carcharodon carcharias. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. . Downloaded on 10 January 2014.
Radiocarbon Dating Suggests White Sharks Can Live 70 Years and Longer, NOAA

Photo credit: Terry Goss, CC BY-SA 3.0

starfish, Pisaster ochraceus

Mysterious disease creates Zombie Starfish

Sick and dying starfish (sea stars) have appeared in a multitude of locations between Alaska and southern California.

“It’s like a zombie wasteland,” says biologist Emily Tucker told Nature. “You’ll see detached arms crawling away from their body.”

Called Sea Star Wasting Disease, it can cause the death of an infected starfish in just a few days. Its effects can be devastating on starfish populations.

The disease has hit before, in southern California in 1983-1984 for example and again in 1997-98. These events were associated with warmer sea temperatures. The current outbreak is more widespread.

It is particularly worrying because one of the starfish affected, Pisaster ochraceus, was the original “keystone species”. This is a species that has a disproportionately large effect on its environment relative to its abundance. Without it the ecosystem would be dramatically different. The concept was first proposed in 1969 using Pisaster ochraceus as a primary example. Within a year of Pisaster ochraceus being removed, biodiversity halved.

Lesions on the animal are the first signs of the disease. Tissue then decays around the lesions which leads to break up of the body and death.

There is a map of where diseased sea-stars have been found at http://data.piscoweb.org/marine1/seastardisease.html

More information at

Photo credit: Steven Pavlov (CC BY-SA 3.0)


Killer Robots Slash Jellyfish

Jellyfish blooms are increasingly causing problems. In Korea, the number of accidents and financial losses caused by jellyfish is estimated at 300 billion won (£1.8 m) per year. To combat the jellyfish, Korean researchers led by Professor Hyeon Myeong are using a team of robots, called JEROS (Jellyfish Elimination Robotic Swarm). These slash and grind the jellyfish, killing 900 kg an hour.

Jellyfish cause the fishing industry to lose money by breaking fishing nets. They sting swimmers. They block the seawater cooling systems of power plants. In 2009, a ten-ton Japanese trawler capsized after the three man crew tried to haul up a net loaded with jellyfish.

Scientists have proposed several reasons why jellyfish blooms are apparently becoming more common around the world’s coasts. One recent suggestion is that “ocean sprawl” may be an important driver of the global increase in jellyfish blooms. Ocean sprawl is the proliferation of artificial structures associated with shipping, aquaculture, other coastal industries and coastal protection. The theory is that the structures provide habitat for jellyfish polyps thus causing the increase in jellies.1 Another theory is over-fishing of predators like turtles. Polluted waters – where fertiliser run-off etc causes plankton blooms – increase the food for jellyfish.

Will robots exterminating jellyfish solve any jellyfish problems? What happens to the jellyfish parts that have been cut up?

Reducing the underlying cause of the jellyfish blooms is surely more of a solution than producing billions of jellyfish bits.

The aquatic robot designed by the Korean Higher Institute of Science and Technology (KAIST) has a mountable grinding part buoyed by two cylinders that use motors to move forward and reverse, as well as rotate 360 degrees. Data from a GIS (geographic information system) map is used to specify the region for jellyfish extermination. JEROS then navigates autonomously using a GPS (Global Positioning System) receiver and an INS (inertial navigation system).

The assembly robots maintain a set formation pattern, while calculating its course to perform jellyfish extermination. The advantage of this method is that there is no need for individual control of the robots. Only the leader robot requires the calculated path, and the other robots can simply follow in a formation by exchanging their location information via wireless communication (ZigBee).

JEROS uses its propulsion speed to capture jellyfish into the grinding part on the bottom, which sucks the jellyfish toward the propeller to be exterminated.

Further Reading
Kaist: Korean Higher Institute of Science and Technology

Jellyfish Blooms and Their Effects in the Sea of Japan

1Is global ocean sprawl a cause of jellyfish blooms?
Carlos M Duartee et al Frontiers in Ecology and the Environment 2013 11:2, 91-97

Crown of thorns starfish, COTS

Sea Simulator to Solve Seas’ Mysteries

Australia today opened the National Sea Simulator to tackle ocean issues. This research aquarium is aiming to discover:

  • How well will the Great Barrier Reef adapt to a changing climate and more acidic oceans?

  • Why do crown-of-thorns starfish populations periodically boom?
  • Can we develop technologies to control crown-of thorns and give the Reef time to adapt to a changing climate?
  • Is coral bleaching simply a reaction to hot oceans or is something more complex happening?
  • Whether bacteria and viruses will become dominant as climate change takes hold?

The $35 million SeaSim gets closer to replicating the conditions of the open ocean, a reef lagoon or flooding rivers than any other facility in the world.

“It’s awesome,” says Australian Institute of Marine Science (AIMS) researcher Mike Hall. “When we started planning SeaSim we visited over 40 marine aquariums around the world to identify key attributes of the perfect research facility. What we’ve built takes the best in the world and adds new technologies and an incredible level of automation and control.”

“In each tank we can automatically control many parameters – from water temperature to ocean acidification to salinity to lighting to nutrients and water quality etc.”

“SeaSim will allow marine scientists the world over to test observations, assumptions and models. It will allow the development of technologies to assist aquaculture and fisheries management.”

“Fighting the crown-of-thorns starfish is one of the highest priorities for SeaSim,” says John Gunn, the AIMS CEO. “We need to understand why starfish populations periodically boom leading to massive reef destruction. Is it due to nutrients in flood waters or are more complex factors at play?”

“Crown-of-thorns talk to each other with chemicals – they gather in groups and they ‘run away’ when predators such as the Giant Triton move in to feed on them. Could we use those chemical signals to trick starfish into congregating or dispersing – making physical removal easier? We hope to answer these and many other questions about the starfish with the help of SeaSim,”

SeaSim brings together a reliable, consistent supply of high quality seawater with the technology to enable precise control over environmental factors like temperature, light, acidity, salinity, sedimentation and contaminants. It integrates technology developed in the industrial process sector—-used to control and manipulate seawater and ambient conditions—-with aquarium technologies of plant and animal husbandry.

The Sea Simulator was opened by Senator Kim Carr who said the Government had funded the SeaSim because it was essential for Australia to better understand the impact of events such as ocean warming and acidification, outbreaks of natural predators such as the Crown-of-Thorns Starfish and pollution.

Further Reading:
About SeaSim, the National Sea Simulator