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 Litter is present throughout the world’s oceans: 1,220 species affected
27.03.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

nachricht International network connects experimental research in European waters
21.03.2017 | 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: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Unique genome architectures after fertilisation in single-cell embryos

30.03.2017 | Life Sciences

Pinball at the atomic level

30.03.2017 | Physics and Astronomy

Organic-inorganic heterostructures with programmable electronic properties

30.03.2017 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>