Study: Overfishing Large Sharks Impacts Entire Marine Ecosystem, Shrinks Shellfish Population

Fewer big sharks in the oceans mean that bay scallops and other shellfish may be harder to find at the market, according to an article in the March 30 issue of the journal Science, tying two unlikely links in the food web to the same fate.

A team of Canadian and American ecologists, led by world-renowned fisheries biologist Ransom Myers at Dalhousie University, has found that overfishing the largest predatory sharks, such as the bull, great white, dusky, and hammerhead sharks, along the Atlantic Coast of the United States has led to an explosion of their ray, skate, and small shark prey species.
"With fewer sharks around, the species they prey upon – like cownose rays – have increased in numbers, and in turn, hordes of cownose rays dining on bay scallops, have wiped the scallops out," says co-author Julia Baum of Dalhousie.

"This ecological event is having a large impact on local communities that depend so much on healthy fisheries," says Charles Peterson, a professor of marine sciences biology and ecology at the Institute of Marine Sciences, University of North Carolina at Chapel Hill and co-leader of the study.

The research builds upon an earlier study by Myers and Baum, published in Science in 2003, which used data from commercial fisheries to show rapid declines in the great sharks of the northwest Atlantic since the mid-1980s. Now, by examining a dozen different research surveys from 1970-2005 along the eastern U.S. coast, the research team has found that their original study underestimated the extent of the declines: scalloped hammerhead and tiger sharks may have declined by more than 97 percent; bull, dusky, and smooth hammerhead sharks by more than 99 percent.

"Large sharks have been functionally eliminated from the east coast of the U.S., meaning that they can no longer perform their ecosystem role as top predators," says Baum. "The extent of the declines shouldn't be a surprise considering how heavily large sharks have been fished in recent decades to meet the growing worldwide demand for shark fins and meat."

Sharks are targeted in numerous fisheries, and they also are snagged as bycatch in fisheries targeting tunas and swordfish in both U.S. and high seas fisheries. As many as 73 million sharks are killed worldwide each year for the finning trade, and the number is escalating rapidly.
Ecologists have long predicted that the demise of top predators could trigger destructive consequences. Researching such effects, however, has been a challenge.

"This is the first published field experiment to demonstrate that the loss of sharks is cascading through ocean ecosystems and inflicting collateral damage on food fisheries such as scallops," says Ellen Pikitch, a professor at the University of Miami Rosenstiel School of Marine and Atmospheric Science and executive director of the Pew Institute for Ocean Science. "These unforeseen and devastating impacts underscore the need to take a more holistic ecosystem-based approach to fisheries management."

As great shark populations plummeted, their elasmobranch prey—rays, skates, and smaller sharks—increased considerably, according to research surveys looking at the past 16 to 35 years. Cownose rays are most conspicuous among the 12 species showing increases because of their near-shore migrations. With an average population increase of about eight percent per year, the east coast cownose ray population may now number as many as 40 million. The rays, which can grow to be more than four feet across, eat large quantities of bivalves, including bay scallops, oysters, soft-shell and hard clams, in the bays and estuaries they frequent during summer and migrate through during fall and spring.

In the early 1980s when Peterson sampled bay scallops in North Carolina sounds in late summer before and after the cownose rays passed through, he found that most scallops survived the ray predation, allowing the scallop population to support a fishery and still replenish itself each year. In contrast, sampling by Peterson and co-author Sean Powers in recent years—after the cownose ray population explosion—showed that the migrating rays consumed nearly all adult bay scallops in the area, except those protected inside fences that the researchers had put up to keep the rays out. By 2004, cownose rays had completely devastated the scallop population, terminating North Carolina's century-old bay scallop fishery.
"Increased predation by cownose rays also may inhibit recovery of oysters and clams from the effects of overexploitation, disease, habitat destruction, and pollution, which already have depressed these species," says Peterson, noting shellfish declines in areas occupied by cownose rays and examples of stable or growing shellfish populations in areas beyond the ray's northernmost limit.

Ecosystem effects of increases in the other ray, skate, and smaller shark species are unknown, but like the cownose ray, may also be cascading down to species lower in the food web.
"Despite the difficulty of piecing together ecosystem impacts of overfishing," co-author Travis Shepherd of Dalhousie emphasizes, "the real challenge will be to move beyond retrospective analyses and instead prevent ecosystem-wide changes from happening in the first place."
"Our study provides evidence that the loss of great sharks triggers changes that cascade throughout coastal food webs," says Baum. "Solutions include enhancing protection of great sharks by substantially reducing fishing pressure on all of these species and enforcing bans on shark finning both in national waters and on the high seas."

"Maintaining the populations of top predators is critical for sustaining healthy oceanic ecosystems," says Peterson. "Despite the vastness of the oceans, its organisms are interconnected, meaning that changes at one level have implications several steps removed. Through our work, the ocean is not so unfathomable, and we know better now why sharks matter."

SHARKWATER

For filmmaker Rob Stewart, exploring sharks began as an underwater adventure. What it turned into was a beautiful and dangerous life journey into the balance of life on earth.
Driven by passion fed from a lifelong fascination with sharks, Stewart debunks historical stereotypes and media depictions of sharks as bloodthirsty, man-eating monsters and reveals the reality of sharks as pillars in the evolution of the seas.

Filmed in visually stunning, high definition video, Sharkwater takes you into the most shark rich waters of the world, exposing the exploitation and corruption surrounding the world's shark populations in the marine reserves of Cocos Island, Costa Rica and the Galapagos Islands, Ecuador.

In an effort to protect sharks, Stewart teams up with renegade conservationist Paul Watson of the Sea Shepherd Conservation Society. Their unbelievable adventure together starts with a battle between the Sea Shepherd and shark poachers in Guatemala, resulting in pirate boat rammings, gunboat chases, mafia espionage, corrupt court systems and attempted murder charges, forcing them to flee for their lives.

Through it all, Stewart discovers these magnificent creatures have gone from predator to prey, and how despite surviving the earth's history of mass extinctions, they could easily be wiped out within a few years due to human greed.

Stewart's remarkable journey of courage and determination changes from a mission to save the world's sharks, into a fight for his life, and that of humankind.

Will your house flood?

Most people are wondering how your property will fare in a world with higher sea-levels? Here's a tool that could help. Click Here! Once the site has loaded use your mouse to drag the map around and find the area you live in, the slider at on the left side zooms in and out, and at the top then choose between 1 metre to 14 metres of sea-level rise. However, I think who put this site together, just looked at altitude. Since, the shaded flooded areas that occur, when you select 3 m of sea-level rise, is simply land with an elevation of 3 m above current sea-level. I'm saying this because the shaded areas will not include areas that may be on higher ground but are nevertheless at greater risk of floods and storms. This site can take a while to load everything, so be patient! It very interesting.

Taiwan discovers frozen natural gas

Taiwan has found off its coast huge deposits of frozen natural gas, known as the 'ice that burns' and billed as the energy source of the future, a newspaper said Saturday.A team of Taiwanese and Japanese researchers have succeeded in extracting samples of methane hydrate from the ocean floor off Taiwan's southwest coast and will publish their report in May, the Liberty Times reported.The team began its exploration two years ago, after US and Japanese scientists suspected methane hydrate deposits in the region through monitoring by satellite and scientific equipments.Relying on a deep-sea remote-controlled research ship, the team recently extracted crystallized methane hydrate from a depth of 1,100 metres and recorded how it began to melt at 500-metre depth and vaporize at 400-metre depth.Methane hydrate, in its original form, looks like whitish-yellow ice or ice cream. But at room temperature, it vaporizes and can be ignited, thus the name 'the ice that burns'.'One unit of methane hydrate contains 170 units of natural gas. So the ocean floor is like a gas cylinder holding compressed methane hydrate in crystal form,' Professor Yang Tsan-yao from the National Taiwan University and one of the team members was quoted as saying. The team estimates that Taiwan's southwest coast holds about 600 billion cubic metres of methane hydrate, enough to meet Taiwan's energy needs for 60 years.Several countries, including Japan, the US and Canada, have begun to explore methane hydrate - also called the 'greenhouse energy' - with Japan hoping to start commercial exploration in 2010.

Biggest, Smallest, Fastest, Deepest:Marine Animal Records

Whales and Dolphins

Largest Whale: Blue Whale, Balaenoptera musculusfemale: 33.27 meters (109 feet 3.5 inches) 190 tons estimated weightmale: 32.64 meters (107 feet 1 inch)Both captured near the South Shetland Islands in 1926

Largest Fin Whale, Balaenoptera physalus 90 feet, 97 tons estimated weight

Largest Sei Whale, Balaeonoptera borealis 72 feet, 45 tons estimated weight

Largest Sperm Whale, Physeter catodon 67 feet 10 inches, 72 tons estimated weight

Largest Humpback Whale, Megaptera novaeangliae 65 feet, 64 tons estimated weight

Largest Gray Whale, Eschrichtius robustus 51 feet, 39 tons

Fastest Swimming Baleen Whale (short distance)Sei Whale, Balaenoptera borealis: 35 miles per hour in short bursts

Fastest Swimming Dolphin:

Dall's porpoise, Phocoenoides dalli, recorded at 56 km/hr
Killer Whale, Orcinus orca , recorded at 56 km/hr
Common Dolphin, Delphinus delphis - 37 km/hr

Seals and Sea Lions

Largest Northern Elephant Seal, Mirounga angustirostris: 18 feet, taken in 1852 off Santa Barbara Island, 15 feet 7 inches taken in 1929 off San Diego

Largest Southern Elephant Seal, Mirounga leonina: 21 feet, 4 inches, taken near South Georgia Island in 1913

Smallest Pinniped: Baikal Seal, Pusa sibiricaAdults are 4 feet 6 inches and 140 pounds

Fastest Swimming Pinniped: California Sea Lion, Zalophus californianus 25 miles per hour

Greatest Age for a Pinniped:Ringed Seal, Phoca hispida: 43 years, collected on Baffin Island and based on growth layers in the teethGrey Seal, Halichoerus grypus, 41-42 years, kept in captivity in Sweden from 1901-1942

Fish

Largest Fish Whale Shark, Rhinodon typus 59 feet, for a specimen captured in Thailand in 1919

Largest Basking Shark, Cetorhinus maximus 45 feet. Weight estimated at 32,000 pounds

Largest Tiger Shark, Galeocerdo cuvieri 20 feet, 10 inches, 2070 pounds

Largest Hammerhead Shark, Sphyrna mokarran 18 feet, 4 inches, 1,860 pounds

Largest Thresher Shark, Alopias vulpinus 18 feet, 1,100 pounds

Largest Six-gill Shark, Hexanchus griseus 15 feet, 1,300 pounds

Heaviest Fish in the Class Ostyichtheys (bony fish)Ocean Sunfish, Mola mola: 10 feet in length, 14 feet between dorsal and anal fins, 4,928 pounds, struck and killed by a ship off Australia in 1908

Longest Fish in the Class Ostyichtheys (bony fish)Russian Sturgeon, Acipenser huso: 24 feet in length, weight 1,470 kg (3,250 pounds) caught in the Volga river in 1827

Shortest Marine FishSchindleria praematurus, found in Samoa in the South Pacific: 12-19 mm in length, weight 2 mg.

Fastest Fish:

Sailfish, Istiophorus platypterus: 68.18 mph
Mako Shark, Isurus oxyrinchus: 60 mph
Marlin, Tetrapturus sp. 50 mph
Wahoo, Acanthocybium solandri 48.5 mph
Bluefin Tuna, Thunnus thynnus 43.4 mph
Blue Shark, Prionace glauca 43 mph
Bonefish, Albula vulpes 40 mph
Swordfish, Xiphius gladius 40 mph

Slowest Fish:Sea Horse 0.01 mph

Echinoderms

Largest Sea Star: Evasterias echinosomo 96 cm (37.79 inches) in diameter, weight 5 kg (11 pounds), collected in the North Pacific

Smallest Sea Star: Leptychaster propinquus 1.83 cm (0.72 inches) total diameter

Deepest Sea Star: Eremicaster tenebrariusCollected in 7,630 meters (25,032 feet)

Fastest Sea Star: Sun Star, Pycnopodia helianthoides 75 cm per minute (0.027 miles per hour)

Largest Sea Urchin: Sperosoma giganteumTest diameter of 38 cm (13 inches)

Smallest Sea Urchin: Echinocyamus scaberTest diameter of 5.5 mm (0.21 inches)

Deepest Sea Urchin: Unidentified specimentaken from 7,250 meters (23,786 feet) near Indonesia in 1951

Largest Sea Cucumber: Members of the genus Stichopus have been measured up to 1.3 meters (40 inches) in length and 20 cm (8 inches) in diameter

Smallest Sea Cucumber: Rhabdomolgus ruber, found in the North Sea10 mm (0.39 inches) in length

Deepest Sea Cucumber: Unidentified specimen taken from the Philippine trench in 1951 in 10,190 meters (33,431 feet)

Largest Crinoid: Helimoetra glacialis, found in the Northeast Pacific90 cm (36 inches) in diameter

Smallest Crinoid: Unidentified species with a diameter of 3 cm (1.18 inches)

Deepest Crinoid: Unidentified specimen taken from the Kermadec Trench in 1951 in 8,210 meters (26,935 feet)

Crustaceans

Largest Crustacean: Giant spider crab Macrocheira kaempferiIndividuals can measure 12-14 inches across the body, with a claw span of 8-9 feet. There is a report of a crab weighing 14 pounds with a claw span of 12 feet.

Smallest Crab: Pea crabs in the family Pinnotheridae are about .25 inches across the shell

Heaviest Crustacean: Atlantic Lobster The record, however goes to a lobster weighing 44 pounds, 4 ounces, which was caught in Nova Scotia waters.

Molluscs

Heaviest Mollusc (and heaviest invertebrate): The giant squid (Architeuthis sp.)The largest giant squid ever recorded (Architeuthis princeps) was captured in 1878. One of the "arms" (probably a tentacle) measured 35 feet long. It is estimated that the animal weighed in the neighbourhood of 4000 pounds.

Largest Clams: Tridacna gigas, with a length of 137cm, as reported by Rosewater, J. 1965. The family Tridacnidae in the Indo-Pacific. Indo-Pacific Mollusca 1: 347-396. Tridacna derasa, found on coral reefs in the South Pacific. One was collected on the Great Barrier Reef in 1917 that measured 49 inches by 29 inches, and weighed 579.5 pounds.

Largest Gastropod: Syrinx aruanus, the trumpet or baler conch found off the coast of Australia. In 1979, a 40 pound animal was found with a shell that measured 30.4 inches in length and 39.75 inches in girth.

Cnidarians

Largest Jellyfish: Cyanea arctica, found in the North AtlanticSpecimens have been measured up to 7 feet 6 inches across the bell with a tentacle of 120 feet.

Porifera

Largest Sponge: Xestospongia muta, the barrel sponge, found in tropical coastal waters. Some individuals in the Caribbean measure 6-8 feet tall, and 6-8 feet across. It should be noted, however, that some species of encrusting sponge can cover a very large area.

Seaweed

Largest Seaweed: Macrocystis pyrifera, a brown algae called the giant kelp. The longest recorded length is 54 metres long! M. pyrifera is the type of kelp that makes up the majority of the giant kelp forests off the California coast.

Disaster as Thousands of Harp Seals 'Assumed' Dead Over Lack of Ice Floes; '100% Pup Mortality'

Charlottetown, Canada (Mar 27, 2007 17:33 EST) Thousands of harp seal pups are assumed dead in Canada's Gulf of St. Lawrence due to the lack of ice floes, which mother seals require to give birth and nurse their pups successfully. Experts with IFAW (International Fund for Animal Welfare - www.ifaw.org) have been carrying out daily surveillance flights over the region. They report that the Gulf of St. Lawrence, which is the annual birthing ground of hundreds of thousands of harp seals, is essentially devoid of both ice and seals.
"The conditions this year are disastrous. I've surveyed this region for six years and I haven't seen anything like this" said Sheryl Fink, a senior researcher with IFAW. "There is wide open water and almost no seals. I only saw a handful of adult harp seals and even fewer pups, where normally we should be seeing thousands and thousands of seals."
The ice conditions this year are among the worst on record. Scientists have recorded below average ice conditions in the Gulf of St. Lawrence and off Newfoundland for the past nine out of 11 years. In 2002, 75% of harp seal pups born in the Gulf died due to lack of ice before the hunt even began. This year, the ice conditions appear to be even worse than in 2002 and scientists with IFAW are concerned that pup mortality will be extremely high.
"It's highly likely that this year we could have close to 100% pup mortality in the Gulf of St. Lawrence due to the poor ice conditions caused by rising temperatures," said Dr. David Lavigne, IFAW's science advisor, who recently co-authored a report on the impacts of global warming on harp seals.
Experts with Canada's Department of Fisheries and Oceans (DFO), which monitors the harp seal population and sets targets for annual commercial seal hunt in Canada, have also acknowledged the increase in seal pup mortality this year. It is cited as one reason why the Canadian government has yet to announce the total allowable catch (TAC) or official start date of the this year's hunt, which is due to begin any day.
"It would be reckless for the government to allow the hunt to proceed this year, given the high pup mortality that has apparently occurred," said Fink. "We may not be able to save these seals from the effects of global warming, but the Canadian government can save the survivors from being hunted. I can only hope that they will do the right thing and cancel the hunt."
The Canadian government has permitted nearly one million seals to be killed in the past three years. The government quotas have continually exceeded the number of seals that can be safely removed without causing the population to decline. Last year, the TAC was set at 335,000 seals (far above the estimated sustainable level of 250,000) and the total number of seals reported killed was over 354,000 - exceeding the legal limit by 19,000 animals. Of the 354,000 seals killed last year, 98% were under three months of age.

Somalia: Pirates Rule the World's Most Dangerous Waters

Fred OluochNairobi
The hijacking of MV Rozen by pirates off the coast of Somalia is the latest in a series of hijackings that have been going on for years since Somalia became stateless in 1991.
The ship was on its way to Kenya after offloading 1,800 tonnes of maize, rice and vegetables, when pirates stuck at Ras Shuful off the Somali coast.
The crew of six Kenyans and six Sri Lankans had delivered cargo to different ports on behalf of the World Food Programme.
Though the Somalia Transitional Federal Government (TFG) is struggling to restore civil authority in Somalia, pirates continue to operate off the Somalia coast with impunity. Cases of piracy on the coast increased sharply in 2005, when a total of 48 vessels were attacked and 35 detained with crew and cargo.
Indeed, Somali waters are currently the most dangerous in the world, forcing some shippers to withdraw their operations from the region, while the few that continue plying the route do so at a high risk.
Yet, the route remains important for the region and the global sea trade. Piracy in the area is also encouraged by illegal fishing, which is extremely lucrative given that there is no government in place to monitor deep-sea fishing.
In March last year, a suspected pirate was killed when a group tried to attack a US navy ship off the coast of Somalia.
Various attempts by countries in the region to come up with anti-piracy measures have done little to stamp out the menace in Somali waters.
For example, 10 Somali pirates were last November jailed for seven years each after a trial in Kenya.

In February last year, various countries from the region and observers from the UK, the US, Australia, Bangladesh, Sri Lanka and India, converged on Mombasa to brainstorm on how to curb piracy and armed raids on ships in the Somali waters.
However, a full-fledged monitoring programme was found to be too costly for the struggling economies of the region.
Again, an attempt by the TFG to contract a private security firm to combat persistent insecurity along Somalia's 2,000 km coastline was met with controversy when critics argued that Top Cat marine Security of the US, did not have the capacity to carry out such an operation. TFG had signed a $55 million agreement with Top Cat to tackle piracy in the Horn of Africa.