Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New Sonar Method Offers Way to Assess Health of Squid Fisheries

08.02.2006


Scientists devise technique to detect squid egg clusters on the seafloor


California’s $30-million-a-year squid fishery has quadrupled in the past decade, but until now there has been no way to assess the continuing viability of squid stocks. Scientists have demonstrated new sonar methods to detect egg clusters of squid (Loligo opalescens), pictured above, off Monterey, California. (Photo by Roger B. Hanlon, Marine Biological Laboratory)


Squid return annually to spawn and lay clusters of finger-sized egg capsules on the seafloor off Monterey, California. (Photo courtesy Roger B. Hanlon, Marine Biological Laboratory)



California’s $30-million-a-year squid fishery has quadrupled in the past decade, but until now there has been no way to assess the continuing viability of squid stocks. A multi-institutional team of scientists this month reported a new sonar technique to locate squid egg clusters in the murky depths, offering a window onto next year’s potential squid population in its nursery.

The scientists demonstrated the new sonar methods off the coast of Monterey, California, where fishermen harvest squid in April and May as the squid return annually to spawn and lay clusters of finger-sized egg capsules on the seafloor. The scientists learned how to distinguish subtle sound signals reflected off gelatinous egg clusters and the adjacent sandy seafloor, and they could detect egg clusters less than 20 inches (0.5 meters) across.


“This method provides an efficient way to map distributions and estimate abundances of squid eggs and monitor them year to year to get a census for next year’s population,” said Kenneth G. Foote, a marine acoustics expert at Woods Hole Oceanographic Institution (WHOI) in Massachusetts and lead author of an article published in the February Journal of the Acoustical Society of America. “It has immediate potential to give resource managers sound scientific information to make decisions on how to sustain the fishery. Otherwise, they’re just guessing.”

The scientific team combined the expertise of Foote; Roger T. Hanlon, a biologist at the neighboring Marine Biological Laboratory (MBL) in Woods Hole and a leading authority on squid behavior; and Pat J. Iampietro and Rikk G. Kvitek, seafloor mapping experts at California State University (CSU), Monterey Bay. The research was funded by the Sea Grant Essential Fish Habitat Program.

The researchers developed and tested the new sonar methods off Monterey, where squid fishing begun in the 1860s has intensified as other fisheries have declined and the market for squid has increased, Hanlon said. Every spring squid (Loligo opalescens) return to spawn a few hundred yards offshore, near Cannery Row, in waters 65 to 200 feet (20 to 60 meters) deep. They deposit capsules, each containing 150 to 300 embryos, which are attached to each other, first forming small clumps called mops that later cluster into egg beds up to several meters in diameter. The primary spawning ground in Monterey covers an area of about four square miles (10 square kilometers).

Surveying the underwater squid nursery with divers or underwater cameras is too difficult, time-consuming, and expensive, the scientists said. Using the new sonar methods, the entire Monterey spawning area could be surveyed in less than 40 hours at relatively low cost, with a suitably equipped boat towing a sidescan sonar.

Solving the problem first required a way to detect squid eggs. Hanlon approached Foote, who was game to try but not initially optimistic. “You have to be able to distinguish weak signals echoing off small targets from powerful signals echoing off much larger targets,” Foote said.

The team conducted experiments by towing a sidescan sonar with the CSU Seafloor Mapping Lab’s research vessel MacGinitie. They tested different ways to tune sound wave frequencies, adjust the angle of the sonar, and tow it at various speeds and heights off the seafloor—all in an effort to optimize signals reflected back from the egg clusters. Foote analyzed the raw acoustic data to tease out signals representing egg clusters and seafloor and translated the sound data into images.

The results were seafloor maps clearly showing a characteristic mottling pattern—squid egg clusters—distributed on the seafloor. Underwater cameras confirmed that the sonar images represented egg clusters.

Hanlon said the sonar method provides a crucial tool for estimating how well squid are reproducing, learning more about squid behavior, and identifying ways to monitor a valuable fishery while protecting a species that is a key link in marine food chain. Squid are a staple in the diets of 19 fish, nine bird, and two marine mammal species. They are also a popular restaurant item as calamari.

Since fishing usually commences as soon as squid appear nearshore in Monterey Bay, fishermen may be catching large numbers of squid before they have a chance to spawn, Hanlon said.

“Fishing while squid are actively mating and laying eggs can remove certain sizes and sexes of squid schools and interfere with complex sexual selection behaviors that are crucial to the gene flow and vigor of the population,” Hanlon said. “If we can detect when the egg clusters appear, then wait a few days for the squid to spawn, we can help ensure that squid can complete their mating cycle. That way, they will lay enough eggs to provide squid to fish next year, and the squid gene pool will continue to flow by natural, not unnatural, selection.”

“We aim for this technique to help create a win-win situation,” he said. “Fishermen harvest the same amount of calamari this year and in future years, and meanwhile we don’t interfere with squid population genetics and have enough squid for the ocean, too.”

Foote and Hanlon said the sonar techniques could be adapted and applied to more effectively manage other squid fisheries around the world, including major fisheries in South Africa, Japan, the Falkland Islands, and perhaps on the United States East Coast.

Shelley Dawicki | EurekAlert!
Further information:
http://www.whoi.edu/mr/pr.do?id=10206
http://www.whoi.edu

More articles from Ecology, The Environment and Conservation:

nachricht Preservation of floodplains is flood protection
27.09.2017 | Technische Universität München

nachricht Conservationists are sounding the alarm: parrots much more threatened than assumed
15.09.2017 | Justus-Liebig-Universität Gießen

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: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>