All posts by 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
Parrotfish in fishing net

Caribbean coral reefs gone within 20 years

Most Caribbean coral reefs may disappear in the next 20 years, if something isn’t done, a new report warns.

Caribbean corals have declined by more than 50% since the 1970s. But the good news is that the trend can be reversed. Restoring parrotfish populations and improving other management strategies, such as protection from overfishing and excessive coastal pollution, could help the reefs recover and make them more resilient to future climate change impacts. So says the report, Status and Trends of Caribbean Coral Reefs: 1970-2012, which is the result of the work of 90 experts over the course of three years. It contains the analysis of more than 35,000 surveys conducted at 90 Caribbean locations since 1970, including studies of corals, seaweeds, grazing sea urchins and fish.

The main problem faced by the reefs is the loss of grazers, like parrotfish in the region. Climate change, which has long been blamed for coral degradation does pose a serious threat by making oceans more acidic and causing coral bleaching, but the report shows that the loss of parrotfish and sea urchins has, in fact, been the key driver of coral decline in the Caribbean.

Sea urchin on caribbean coral reef
Sea Urchin

Disease led to mass mortality of the sea urchin in 1983 whilst over-fishing has brought the parrotfish population to the brink of extinction in some places. The loss of these species allows algae, on which they feed, to smother the reefs.

Parrotfish are missing from Caribbean Coral Reefs
Parrotfish, photo credit: Tim Nicholson

“Even if we could somehow make climate change disappear tomorrow, these reefs would continue their decline,” says Jeremy Jackson, lead author of the report. “We must immediately address the grazing problem for the reefs to stand any chance of surviving future climate shifts.”

The report also shows that some of the healthiest Caribbean coral reefs are those that harbour vigorous populations of grazing parrotfish. These include the Flower Garden Banks National Marine Sanctuary in the northern Gulf of Mexico, Bermuda and Bonaire, all of which have restricted or banned fishing practices that harm parrotfish, such as fish traps and spearfishing. Other countries are following suit.

Local decisions and actions can make a big difference to the reefs. Bermuda, for example, has 39% coral cover whilst most areas have less than 14%.

Reefs where parrotfish are not protected have suffered tragic declines, including Jamaica, the entire Florida Reef Tract from Miami to Key West, and the U.S. Virgin Islands.

“The rate at which the Caribbean corals have been declining is truly alarming,” says Carl Gustaf Lundin, Director of IUCN’s Global Marine and Polar Programme. “But this study brings some very encouraging news: the fate of Caribbean corals is not beyond our control and there are some very concrete steps that we can take to help them recover.”

Healthy coral
Healthy Coral, photo credit: Tim Nicholson

The authors also looked at the impact of invasive species like lionfish, but concluded that although they have “wreaked havoc in Caribbean fish communities…they pale in comparison to the introduction of the unidentified pathogen that caused the die-off of Diadema antillarum or the effects of “White-band disease” on acroporid corals.”

Lionfish, photo credit: Tim Nicholson

The authors of the report recommend adopting conservation and fisheries management strategies that lead to the restoration of parrotfish populations and so restore the balance between algae and coral.

Further Reading:
Status and Trends of Caribbean Coral Reefs: 1970-2012

Deploying Red Tide Detector

Sensors watch for Red Tides

This year an array of sensors are watching for harmful red tides in the Gulf of Maine.

The red tide is caused by the germination of dormant cysts of alga called Alexandrium fundyense, which produces a toxin that can cause paralytic shellfish poisoning. Another name for a red tide is “harmful algal bloom” or HAB.

Scientists have been monitoring red tides for years, so that they can warn people when problems are about to occur. They typically base their annual red tide forecast on the abundance of cysts in bottom sediments combined with a computer model that simulates a range of bloom scenarios based on previous years’ conditions. However, oceanographic conditions are changing which meant that the forecast for both 2010 and 2013 were inaccurate.

This year, then, researchers are using four robotic instruments called Environmental Sample Processors (ESPs) that measure bloom concentration and toxins at several spots along the Gulf of Maine and provide near real-time data on toxic algae which they transmit to shore. The ESPs are mounted to ocean buoys and will detect and estimate concentrations of algal species that cause red tides and one of the potentially fatal toxins they produce.

“The ESPs are not a replacement for state-run programs that monitor naturally occurring marine toxins in shellfish,” said Kohl Kanwit, Director of the Bureau of Public Health for the Maine Department of Marine Resources. “Instead, they provide valuable data on the algal cells and associated toxins in coastal waters, giving managers early warning and a more complete picture of the magnitude and distribution of HAB events.”

Further Reading:
Woods Hole Oceanographic Institute
What is a Red Tide?

Photo credit: Photo by Isaac Rosenthal, Woods Hole Oceanographic Institution & Northeastern University

Endangered Sawfish Strategy Launched

Plan to save sawfish – most endangered fish in the sea

The International Union for Conservation of Nature (IUCN) has released a global strategy to prevent extinction and promote recovery of sawfishes.

The strategy by the IUCN’s Shark Specialist Group was launched at the Sharks International conference in South Africa and coincides with announcements that two West Africa countries – Guinea and Guinea Bissau – are proposing the listing of sawfishes under the Convention on Migratory Species in November, which could significantly boost protections.

Sawfishes have been devastated worldwide by overfishing and habitat loss. “The sawfishes, revered for millennia by coastal cultures around the world, now face greater extinction risk than any other family of marine fish,” the strategy’s co-author, Dr. Nick Dulvy, said. “With this comprehensive strategy, we aim to reignite sawfish reverence and spark conservation action in time to bring these iconic species back from the brink” he added.

Sawfish are very large – reaching up to 7 m. These shark-like rays have distinctive, toothed, snouts from which they get their name. All five species are classified as Endangered or Critically Endangered on the IUCN Red List of Threatened Species. They live in coastal tropical and subtropical waters worldwide, including estuaries and river systems as well as the oceans.

“Although these species are perilously close to extinction in many regions, there are some fairly simple ways to help populations recover. For example, we know that sawfish can actually survive capture quite well if handled properly, and hence, basic education of commercial, subsistence, and recreational fishers is central to our conservation strategy,” said Dr. Colin Simpfendorfer, Professor of Environmental Science at James Cook University in Queensland.

The toothed rostrum (snout) makes sawfish especially prone to entanglement in fishing nets. As many live in estuaries, coastal development and loss of habitat is another factor that has depleted populations. Like other sharks and rays, their slow growth – taking 10 years to reach maturity – makes for a vulnerable population.

To compliment an existing ban on commercial international sawfish trade, the Strategy calls for national and regional actions to prohibit intentional killing of sawfish, minimise mortality of accidental catches, protect sawfish habitats, and ensure effective enforcement of such safeguards.

Further Reading:

Sustainable fishing stamps

Stamping out over-fishing

For the first time, Britain’s Royal Mail has issued stamps championing an environmental issue – and that issue is sustainable fishing. Over-fishing has long been a problem – policy-makers don’t seem to understand if you take more fish out of the sea than can be replaced then you will run out. One way things might change is by consumers voting with their purses and choosing to buy only fish that can be caught sustainably. Research by the Royal Mail, though, has revealed that little is known by the public about which fish are in trouble and which we can eat.

Half of the species illustrated are fish that are at risk in UK waters: Common Skate; Spiny Dogfish (Rock Salmon); Wolffish; Sturgeon and Conger Eel. The other half are species from what are probably sustainable populations and suitable alternatives: Herring; Red Gurnard; Dab; Pouting and Cornish Sardine.

Professor Callum Roberts who acted as consultant for Royal Mail on the stamp issue said: “Marine protected areas that are off limits to fishing could recover endangered species like those on the stamps, as well as providing a boost to the fishing industry through recovered stocks. Only one thousandth of 1% of UK seas are fully protected from fishing at present. To bring back endangered fish species, we need a huge increase in the coverage of such protected areas.”

The Threatened Fish

Common Skate, Dipturus batis

Common Skate, Dipturus batis
The largest skate found in European waters, with females growing up to 285 cm. They can live up to 100 years. Previously widespread – as the name implies – they are now extinct in the Mediterranean and greatly reduced in range around Britain. Retaining and landing common skate is now prohibited in EU waters. Common skate is assessed as Critically Endangered.

Wolffish, Anarhichas lupus

Woffish, Anarhichas lupus
Wolffish live on the seabed. They do not reproduce until they are 8 to 10 years old. Modern fishing methods have severely reduced wolffish numbers, not just by catching the fish but also by destroying their habitat and breeding grounds with intensive, repeated bottom trawling.

Common Skate, Dipturus batis

Conger Eel, Conger conger
This massive fish can grow to almost 3 m (10 ft) long, the females often being bigger than the males. Congers breed only once in their lives, commonly when they reach 5 years old, after which they die. As they breed only once, just about all eels which are caught in fishing nets are juveniles which have not yet reached spawning age. They only become sexually mature during the journey to the spawning areas.

Spiny Dogfish, Squalus acanthias

Spiny Dogfish, Squalus acanthias
More commonly known in the fishmongers as Rock Salmon, the spiny dogfish is critically endangered. It is a long-lived, slow-growing and late-maturing species and therefore particularly vulnerable to fishing. Pregnancy lasts between 18 and 22 months, one of the longest recorded for any vertebrate, and they give birth to live young. Older females produce 10 to 21 pups, but younger ones (who are smaller than 1 m) produce less.

Sturgeon, Acipenser, Huso spp

Sturgeon, Acipenser, Huso spp
Although some sturgeon sold are farmed, those caught in nets should be avoided. According to the Marine Conservation Society (MCS) “The value of wild sturgeon caviar is so high that there is a substantial illegal fishery for sturgeon that is completely unregulated. Consequently many species are in rapid decline.

Fish that are OK to Eat

Pouting or Bib

Pouting or Bib, Trisopterus luscus
Called Pouting on the stamp but known to divers as Bib. A member of the cod family, matures at just 1 to 2 years and around 23 cm long. Pouting is considered an “under-utilised species”: the ones that fishermen don’t catch their full quota of; or they catch them but then discard the fish because no one wants to buy them. Can be used in recipes specifying white fish.


Herring, Clupea harengus
Herring is a familiar fish. Its sustainability depends on the methods of the fishery catching it. Look for certification from the Marine Stewardship Council (MSC) to show that the Herring were caught responsibly.


Red Gurnard, Aspitrigla cuculus
Gurnards are a non-quota species so are often discarded due to low market demand. If we eat these it will stop fish being wasted in this way. Avoid eating immature fish – those less than 25cm – and fresh fish caught in summer during the spawning season.


Cornish Sardine, Sardina pilchardus
Look for MSC certified fish with the Blue tick logo on the package. The most sustainable sardine fishery are the Cornish boats using traditional pilchard drift nets. Sardines and pilchards are the same fish, the larger fish are known and pilchards and the smaller as sardines.


Dab, Limanda limanda
Dab is one of the most abundant fish in the North Sea and can be eaten instead of other flat fish like plaice.

Further reading:
Royal Mail
Fish online: a good site to find out about which other fish to eat or avoid from the Marine Conservation Society

Grey Reef Shark, Carcharhinus amblyrhynchos

Shark-counting divers become citizen scientists

Divers monitor reef shark numbers as accurately, and cheaper, than automated tracking tools, a study suggests.

Shark populations are thought to be declining globally, but a quick search of the IUCN’s Red List shows that for 67% of shark species the population trend is unknown.

It’s difficult to monitor shark numbers due in part to many species’ relatively large home ranges. The large scale (tens to hundreds of km) and long-term (years to decades) monitoring programs are costly. We need to find simple and low-cost methods for monitoring shark populations. One option is using observations made by professional dive guides. But are these reliable and accurate?

Over a period of five years, scientists from The University of Western Australia compared counts of grey reef sharks (Carcharhinus amblyrhynchos) submitted by 62 dive guides, with data collected by acoustic tagging. The grey reef shark is one of the many species whose population trend is unknown due to lack of data. The study was conducted at dive sites in Palau.

Divers as accurate as electronic tagging

The scientists found the number of grey reef sharks observed by dive guides matched those identified by acoustic tagging. They suggest that shark behaviour was unaffected by the divers’ presence. The divers’ data also indicates that the water’s current strength and temperature influence the abundance of sharks at the monitored sites, which corroborates previous telemetry data.

Lead scientist Gabriel Vianna comments “Our study shows that with a little bit of training and a good sampling design, recreational divers collect very useful data that can be used to monitor shark populations over long periods of time and across large spatial areas. Such programs have relatively small costs when compared with other methods currently used.

Shark fishing unsustainable

Scientists have estimated that around 7% of all sharks are killed every year. This exceeds the average rebound rate for many shark populations and explains the ongoing declines in most populations for which data does exist. Using divers could give hard evidence of the decline and help measure whether conservation efforts are succeeding.

Grey shark

Photo copyright Tim Nicholson

Citizen science – cheap and popular

“Citizen science” initiatives, where volunteers collect data as part of a scientific enquiry, are growing in popularity as alternatives to conventional scientific sampling as they offer the opportunity to gather large datasets at reduced cost. The roots of citizen science, though, go back to the very beginnings of modern science.

The divers participating in the study were local residents familiar with the identification of reef sharks in Palau. Guides did their normal days’ diving but were instructed to report the total number of individual sharks of each species observed during the dive. The researchers asked them to be conservative with counts, observing features that could permit individual identification (like pigment patterns, marks and scars) to reduce the potential for repeated counts. Standard questionnaires were completed after the day trips – during which 2 or 3 dives would have been conducted. Each questionnaire contained information on the dive site visited, date, dive time, number of divers in the group, shark species and counts of individual sharks sighted by the dive guide. Dive guides estimated the depth during the sightings, current strength and visibility.

The researchers used acoustic tagging to validate the data collected by the divers. Acoustic tags can be deployed on sharks without affecting their behaviour. Whenever a shark passes within range of an array of acoustic receivers, its presence is logged. This provides an index of relative abundance that can be used to identify trends in the populations over time. The receivers were deployed at depths between 25 and 40 m and recorded the presence of tagged sharks up to 200 m away. The scientists internally tagged 39 sharks – 38 females and 1 male. Ten of these tags were also fitted with pressure sensors, which provided a record of depth of the tagged sharks. Temperature loggers near the dive sites recorded daily temperatures.

White tip reef shark

White tip reef shark, by Tim Nicholson

When to see sharks

Grey reef and whitetip reef sharks (Triaenodon obesus) were present at the monitored sites throughout the year. However, there was seasonal variation in the number of individuals of both species. Less sharks were seen in May, October and November. Sharks were most frequent between March and April. Current and temperature were the key environmental factors affecting shark numbers. Visibility, moon phase and number of divers in the water had little influence on the number of sharks sighted.

The results of the study are reported in the PLoS ONE journal.

Further Reading:

Vianna GMS, Meekan MG, Bornovski TH, Meeuwig JJ (2014) Acoustic Telemetry Validates a Citizen Science Approach for Monitoring Sharks on Coral Reefs. PLoS ONE 9(4): e95565. doi:10.1371/journal.pone.0095565

Boris Worm et al, Global catches, exploitation rates, and rebuilding options for sharks, Marine Policy, Volume 40, July 2013, Pages 194-204, ISSN 0308-597X,

The IUCN Red List of Threatened Species

Tiger Shark Cull

Little Support for Shark Culling

Following another fatal shark attack in Australia, new research finds little support for the shark cull.

A survey of 583 aquarium visitors asked people how they thought the Government should respond to shark bites and found that despite the public’s fears, 87 per cent favoured non-lethal responses.

Only four per cent of those surveyed supported the hunting of sharks.

Another key finding was that only 2-4 percent blamed the Government and only slightly more (6-8 percent) blamed the sharks. Most responsible were thought to be either the swimmer or simply no-one.

Conducted by University of Sydney Lecturer Dr Christopher Neff and funded by the SEA LIFE Conservation Fund, the survey is the first research of its kind. Dr Neff stated, “These responses show that there is little support for government measures that kill sharks and that the public does not blame governments when these tragedies occur.”

“The Australian public is ready for some new options” said Claudette Rechtorik, Director of the SEA LIFE Conservation Fund. She added, “The findings from this data are consistent with what we hear every day. After 77 years of shark culling in New South Wales it is time to consider something else. We…believe the research is important for policymakers to consider given that it suggests that the Government should respond to shark bites with greater public education and non-lethal shark culling measures.”

The research comes as Western Australia seeks to extend its shark cull policy by three years.

Based on state figures released in March, the WA shark cull policy has killed 41 sharks of which 95% were tiger sharks. The sharks ranged in size from 1.7 m (a Mako) to 4.1 m. Ten were already dead: killed by the drum lines. The rest were destroyed. The government has not released any information on the numbers of other animals killed by the drum lines.

Photo credit: Albert Kok


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

North Atlantic Right Whale, Mother and Calf

Speed Limits Save Right Whales

Numbering just 500, the North Atlantic right whale (Eubalaena glacialis) is one of the rarest animals in the world. The whales have been hunted nearly to extinction. Now protected, their biggest threats are being hit by ships and entanglement in fishing gear. With no progress in reducing entanglement deaths, reducing ship collisions has become even more important.

The speed a ship is going means the difference between life and death for the whales. New research has found that if ships are travelling at less than 10 knots then all right whales survive.

When large vessels travel at more than 10 knots, whales are pulled towards the ships’ hulls and propellers with increasing force as the ship goes faster. The whales are also more likely to be run into by ships travelling at speed.

In 2008 America introduced seasonal speed restrictions in right whale feeding areas, migratory corridors and calving areas off the east coast. The original proposals were watered down though – the corridors protected were narrower than the actual migratory routes for example.

Since the speed limits were imposed, no right whales whatsoever have been killed by colliding with ships in the managed areas! A significant boost for whale numbers. The research was published in the Endangered Species Research journal by David W. Laist, Amy R. Knowlton and Daniel Pendleton. The researchers call for the protection for migratory corridors to be widened and the speed limits retained indefinitely. They also want more seasonal restrictions to protect humpback whales. There are people suggesting that dredged channels be exempt from the restrictions, but the researchers point out that because whales must travel across those channels they are at no less risk of being struck and so the dredged channels should stay.

Photo by Wildlife Trust, NOAA Permit #594-1759, (CC BY-NC-SA 2.0)

Further Reading
Laist DW, Knowlton AR, Pendleton D (2014) Effectiveness of mandatory vessel speed limits for protecting North Atlantic right whales. Endang Species Res 23:133-147
The North Atlantic Right Whale Consortium

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