Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Overfishing great sharks wiped out North Carolina bay scallop fishery

02.04.2007
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:
http://www.globalshark.ca
http://www.pewoceanscience.org

More articles from Ecology, The Environment and Conservation:

nachricht Dune ecosystem modelling
26.06.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

nachricht Understanding animal social networks can aid wildlife conservation
23.06.2017 | Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB)

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: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Study shines light on brain cells that coordinate movement

26.06.2017 | Life Sciences

Smooth propagation of spin waves using gold

26.06.2017 | Physics and Astronomy

Switchable DNA mini-machines store information

26.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>