Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

To manage a fishery, you must know how the fish die

12.08.2009
Recreational anglers and commercial fishermen understand you need good fishery management to make sure there will be healthy populations of fish for generations to come.

And making good management decisions rests in large part on understanding the mortality of fish species – how many fish die each year as a result of natural causes and recreational and commercial fishing.

Now researchers at North Carolina State University have utilized a new research method that can give fishery managers a better idea of how fish are dying, so they can make informed decisions on how to ensure a healthy fish population.

Fisheries scientists from NC State have, for the first time, implemented a research strategy that uses both "conventional" tags and ultrasonic telemetry tags (transmitters) to estimate mortality rates. The approach was used in a study on mortality rates of "sub-adult" red drum, which are red drum that are close to adult in size but have not yet begun to reproduce. However, the research methods pioneered in this study could be applied to many other species, including popular fish such as striped bass. Red drum are popular among recreational anglers in many parts of the country, and are also important to commercial fishermen in North Carolina.

The conventional tags offer rewards to recreational and commercial fishermen who catch the tagged fish, creating an incentive for them to contact researchers. This approach lets researchers know how many of the tagged fish have been caught and how many of the fish were subsequently released or harvested, explains Dr. Jeff Buckel, an associate professor of biology at NC State and co-author of the study. This approach provides particularly good data on mortality resulting from commercial and recreational fishing, Buckel says.

The telemetry tags transmit uniquely coded sounds to receivers, allowing researchers to track fish movement in a given area. In this instance, the researchers were using both stationary receivers and mobile hydrophones to track tagged fish in the Neuse River estuary in eastern North Carolina, Buckel says. Telemetry tags provide excellent data on natural mortality, because the tags stop moving once the fish has died. These tags can also detect that a fish has been caught by commercial or recreational fishermen, because the tag will disappear from the study area without swimming past any of the receivers.

"The methodology we used in this study combined good natural mortality data from the telemetry tags with good recreational and commercial fishing mortality data from the conventional tags to give us a more precise estimate of overall mortality for sub-adult red drum," Buckel says. "This is important because, if you have a good understanding of mortality rates, you can make informed decisions about how to manage a fishery in order to ensure its long-term health." For example, the information generated by this study contributed to state and regional assessments of the red drum population.

"This is the first time this approach, using both kinds of tags, has been used in the field," Buckel says, "and it could have significant applications for other species, such as striped bass." One limitation is that the telemetry tags are only useful in relatively confined areas, such as lakes, estuaries or reservoirs – where researchers can place listening devices near exits to determine if a fish has left the waterbody on its own, rather than being caught by a fisherman.

The researchers, led by then-NC State Ph.D. student Nathan Bacheler, focused on sub-adult red drum because North Carolina only allows recreational and commercial fishermen to keep drum that are between 18 inches and 27 inches long. These fish are generally not old enough to reproduce. So researchers wanted to determine whether natural mortality and fishing mortality were limiting the long-term viability of the fishery. Good news fish fans: "Natural mortality was much lower than we previously assumed," Bacheler says, "and the fishing mortality was similar to previous estimates."

The research, "A combined telemetry – tag return approach to estimate fishing and natural mortality rates of an estuarine fish," was funded by North Carolina Sea Grant and is published in the August issue of the Canadian Journal of Fisheries and Aquatic Sciences. The study was co-authored by Bacheler, Buckel, NC State biology professors Dr. Joseph Hightower and Dr. Kenneth Pollock, and Lee Paramore of the North Carolina Division of Marine Fisheries.

Matt Shipman | EurekAlert!
Further information:
http://www.ncsu.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: Salmonella as a tumour medication

HZI researchers developed a bacterial strain that can be used in cancer therapy

Salmonellae are dangerous pathogens that enter the body via contaminated food and can cause severe infections. But these bacteria are also known to target...

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...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

3rd Symposium on Driving Simulation

23.10.2017 | 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

 
Latest News

Single nanoparticle mapping paves the way for better nanotechnology

24.10.2017 | Physics and Astronomy

A quantum spin liquid

24.10.2017 | Physics and Astronomy

Antibiotic resistance: a strain of multidrug-resistant Escherichia coli is on the rise

24.10.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>