Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Bucking Conventional Wisdom, Researchers Find Black Sea Bass Tougher Than Expected

12.03.2014

In a new study, fisheries researchers from North Carolina State University found that black sea bass (Centropristis striata) can usually survive the physical trauma that results from being hauled up from deep water then released at the surface. The finding is part of a larger study of the fish’s mortality rate, which will inform stock assessments designed to help ensure that the black sea bass fishery is sustainable.

Black sea bass are bottom-dwelling fish, and are often caught at depths of greater than 60 feet. When the fish are brought to the surface, the rapid change in pressure causes the fish’s swim bladder to expand. This forces other organs out of the way and can result in visible “barotrauma” – such as the fish’s stomach being forced partially out of its mouth.


Black sea bass with barotrauma (note stomach protruding from mouth). Click to enlarge. Photo: Jeff Buckel

Conventional wisdom long held that this sort of visible barotrauma meant that a fish would die when thrown back into the water. But that’s not true, according to the NC State study.

The research team was attempting to develop accurate estimates of “discard mortality” rates for black sea bass, meaning that they wanted to know what percentage of the fish would die if they were caught and thrown back. Discard mortality rates are used to make informed stock assessments for fish species, because it helps fisheries officials understand how many fish that are caught and released can be expected to survive. Black sea bass are a valuable species for commercial fishing and are also popular with recreational anglers. Millions of black sea bass are caught and released by recreational anglers off the south Atlantic coast of the U.S. each year.

The researchers came up with a novel method for determining the discard mortality rate for black sea bass. First, the researchers worked with a team of scuba divers to tag black sea bass in their natural habitat on the ocean floor. Then the researchers caught, tagged and released the same number of black sea bass in the same area on the same day. The fish tagged on the bottom served as a control group, since they were not subject to changes in atmospheric pressure or other injuries that could be incurred when caught and brought to the surface.

Over the next year, tagged black sea bass were caught by the researchers, or by recreational anglers or commercial fishing operations who returned the tags to the researchers. Researchers could then compare the number of tags returned from the experimental group (those tagged on the surface) to those returned from the control group (those tagged on the bottom). This allowed them to determine discard mortality rates.

The researchers had put the fish in the experimental group into one of four categories: those without visible injury; those with visible barotrauma; those with hook trauma (meaning the hook had caused significant internal injury); and “floaters” – those that couldn’t swim down into the water at all.

To their surprise, the researchers found that approximately 90 percent of the fish in the experimental group with visible barotrauma (but that weren’t floaters) survived. This was about the same survival rate as for fish that exhibited no visible injury at all. Fish with hook trauma had a survival rate of 36 percent, while floaters had a 16 percent survival rate.

“In previous work, estimates of discard mortality were limited to time periods soon after release,” says Paul Rudershausen, a research associate at NC State’s Center for Marine Sciences and Technology and lead author of a paper describing the research. “By tagging a control group, we were able to estimate the long-term effects of injuries associated with fishing.”

In addition to lending key insight into the black sea bass fishery, Rudershausen notes that the study “may give us insight into mortality for other important species with similar characteristics, such as red grouper and gag grouper.”

The paper, “Estimating reef fish discard mortality using surface and bottom tagging: effects of hook injury and barotrauma,” is forthcoming from the Canadian Journal of Fisheries and Aquatic Sciences. The paper was co-authored by Dr. Jeff Buckel and Dr. Joe Hightower, professors of applied ecology at NC State. The researchers worked closely with fisherman Tom Burgess on the project. The work was done under North Carolina Sea Grant Fishery Resource Grant projects 07-FEG-01 and 11-FEG-04.

-shipman-

Note to Editors: The study abstract follows.

“Estimating reef fish discard mortality using surface and bottom tagging: effects of hook injury and barotrauma”

Authors: P. J. Rudershausen, J. A. Buckel, and J.E. Hightower, North Carolina State University

Published: forthcoming, Canadian Journal of Fisheries and Aquatic Sciences

DOI: 10.1139/cjfas-2013-0337

Abstract: We estimated survival rates of discarded black sea bass (Centropristis striata) in various release conditions using tag–recapture data. Fish were captured with traps and hook and line from waters 29–34m deep off coastal North Carolina, USA, marked with internal anchor tags, and observed for release condition. Fish tagged on the bottom using SCUBA served as a control group. Relative return rates for trap-caught fish released at the surface versus bottom provided an estimated survival rate of 0.87 (95% credible interval 0.67–1.18) for surface-released fish. Adjusted for results from the underwater tagging experiment, fish with evidence of external barotrauma had a median survival rate of 0.91 (0.69–1.26) compared with 0.36 (0.17–0.67) for fish with hook trauma and 0.16 (0.08–0.30) for floating or presumably dead fish. Applying these condition-specific estimates of survival to non-tagging fishery data, we estimated a discard survival rate of 0.81 (0.62–1.11) for 11 hook and line data sets from waters 20–35m deep and 0.86 (0.67–1.17) for 10 trap data sets from waters 11–29 m deep. The tag-return approach using a control group with no fishery-associated trauma represents a method to accurately estimate absolute discard survival of physoclistous reef species.

Matt Shipman | EurekAlert!

Further reports about: Black atmospheric pressure black sea bass experimental fishing mortality species

More articles from Ecology, The Environment and Conservation:

nachricht Coorong Fish Hedge Their Bets for Survival
27.03.2015 | University of Adelaide

nachricht Greener Industry If Environmental Authorities Change Strategy
27.03.2015 | University of Gothenburg

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: Experiment Provides the Best Look Yet at 'Warm Dense Matter' at Cores of Giant Planets

In an experiment at the Department of Energy's SLAC National Accelerator Laboratory, scientists precisely measured the temperature and structure of aluminum as...

Im Focus: Energy-autonomous and wireless monitoring protects marine gearboxes

The IPH presents a solution at HANNOVER MESSE 2015 to make ship traffic more reliable while decreasing the maintenance costs at the same time. In cooperation with project partners, the research institute from Hannover, Germany, has developed a sensor system which continuously monitors the condition of the marine gearbox, thus preventing breakdowns. Special feature: the monitoring system works wirelessly and energy-autonomously. The required electrical power is generated where it is needed – directly at the sensor.

As well as cars need to be certified regularly (in Germany by the TÜV – Technical Inspection Association), ships need to be inspected – if the powertrain stops...

Im Focus: 3-D satellite, GPS earthquake maps isolate impacts in real time

Method produced by UI researcher could improve reaction time to deadly, expensive quakes

When an earthquake hits, the faster first responders can get to an impacted area, the more likely infrastructure--and lives--can be saved.

Im Focus: Atlantic Ocean overturning found to slow down already today

The Atlantic overturning is one of Earth’s most important heat transport systems, pumping warm water northwards and cold water southwards. Also known as the Gulf Stream system, it is responsible for the mild climate in northwestern Europe. 

Scientists now found evidence for a slowdown of the overturning – multiple lines of observation suggest that in recent decades, the current system has been...

Im Focus: Robot inspects concrete garage floors and bridge roadways for damage

Because they are regularly subjected to heavy vehicle traffic, emissions, moisture and salt, above- and underground parking garages, as well as bridges, frequently experience large areas of corrosion. Most inspection systems to date have only been capable of inspecting smaller surface areas.

From April 13 to April 17 at the Hannover Messe (hall 2, exhibit booth C16), engineers from the Fraunhofer Institute for Nondestructive Testing IZFP will be...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

World Conference On Regenerative Medicine 2015: Registration And Abstract Submission Now Open

25.03.2015 | Event News

University presidents from all over the world meet in Hamburg

19.03.2015 | Event News

10. CeBiTec Symposium zum Big Data-Problem

17.03.2015 | Event News

 
Latest News

Two Most Destructive Termite Species Forming Superswarms in South Florida

27.03.2015 | Agricultural and Forestry Science

ORNL-Led Team Demonstrates Desalination with Nanoporous Graphene Membrane

27.03.2015 | Materials Sciences

Coorong Fish Hedge Their Bets for Survival

27.03.2015 | Ecology, The Environment and Conservation

VideoLinks
B2B-VideoLinks
More VideoLinks >>>