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 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!
Successful calculation of human and natural influence on cloud formation
04.11.2016 | Goethe-Universität Frankfurt am Main
Invasive Insects Cost the World Billions Per Year
04.10.2016 | University of Adelaide
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
06.12.2016 | Materials Sciences
06.12.2016 | Medical Engineering
06.12.2016 | Power and Electrical Engineering