Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Overfishing great sharks wiped out North Carolina bay scallop fishery

Fewer big sharks in the oceans led to the destruction of North Carolina’s bay scallop fishery and inhibits the recovery of depressed scallop, oyster and clam populations along the U.S. Atlantic Coast, according to an article in the March 30 issue of the journal Science.

A team of Canadian and American ecologists, led by world-renowned fisheries biologist Ransom Myers of Dalhousie University in Halifax, Nova Scotia, has found that overfishing in the Atlantic of the largest predatory sharks, such as the bull, great white, dusky and hammerhead sharks, 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," said co-author Julia Baum of Dalhousie.

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

In 2003, Myers and Baum published a study in Science that showed rapid declines in the great sharks of the northwest Atlantic since the mid-1980s. In the new study, funded by the Pew Institute for Ocean Science, the research team examined a dozen different research surveys from 1970-2005 along the eastern U.S. coast and found that their original study underestimated 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.

"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," Baum said.

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.

With an average population increase of about 8 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 4 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 Peterson sampled bay scallops in North Carolina sounds in late summer before and after the cownose rays passed through and 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 in recent years by Peterson and co-author Sean Powers of the University of South Alabama and the Dauphin Island Sea Lab – 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," said 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.

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," said Ellen Pikitch, executive director of the Pew Institute for Ocean Science and a professor at the University of Miami Rosenstiel School of Marine and Atmospheric Science. "These unforeseen and devastating impacts underscore the need to take a more holistic ecosystem-based approach to fisheries management."

"Maintaining the populations of top predators is critical for sustaining healthy oceanic ecosystems," said 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."

Solutions to the problem, Baum said, "include enhancing protection of great sharks by substantially reducing fishing pressure on all of the shark species and enforcing bans on shark finning both in national waters and on the high seas."

Clinton Colmenares | EurekAlert!
Further information:

More articles from Ecology, The Environment and Conservation:

nachricht Dispersal of Fish Eggs by Water Birds – Just a Myth?
19.02.2018 | Universität Basel

nachricht Removing fossil fuel subsidies will not reduce CO2 emissions as much as hoped
08.02.2018 | International Institute for Applied Systems Analysis (IIASA)

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1

In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.

Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...

Im Focus: Alliance „OLED Licht Forum“ – Key partner for OLED lighting solutions

Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.

They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

Im Focus: Tiny implants for cells are functional in vivo

For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.

In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...

Im Focus: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

Latest News

TRAPPIST-1 planets provide clues to the nature of habitable worlds

21.03.2018 | Physics and Astronomy

The search for dark matter widens

21.03.2018 | Materials Sciences

Natural enemies reduce pesticide use

21.03.2018 | Life Sciences

Science & Research
Overview of more VideoLinks >>>