Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Test fishery Points to Success of Halibut Excluder

09.05.2007
Net modification results in 52% halibut bycatch reduction

Recent test fishing of a halibut excluder device on trawl nets fishing for Pacific cod in the Gulf of Alaska points to a significant reduction of halibut bycatch. The test fishery was coordinated by the cooperative research program of the Marine Conservation Alliance Foundation (MCAF) in conjunction with Dr. Craig Rose of the National Oceanic and Atmospheric Administration’s Alaska Fishery Science Center and the help of Kodiak fishermen.

“This shows what happens when fishermen, scientists, and industry put their heads together to tackle even the most difficult problems,” said John Gauvin, MCAF’s cooperative research coordinator. “We produced a practical device that reduces halibut bycatch in the Gulf trawl fishery by over 50%. The test shows that the device also reduced the catch of cod by 20-30% but from our preliminary look at the cod size data, the cod that are escaping are mostly smaller fish that are less valuable in the market and best returned to the sea.”

Gauvin noted that these results are considered preliminary and more analysis of the data will occur over the coming weeks to identify important factors affecting halibut and cod escapement. This will include a more detailed examination of size gradients for cod escapement and a breakdown of the escapement rate for halibut of different sizes. The researchers are also interested in how tow-by-tow halibut escapement rates are affected by the cod catch rates for those tows. Once the analysis is complete, the draft report will be reviewed by the North Pacific Fishery Management Council’s Scientific and Statistical Committee later this year. The need for such a device was apparent because of an increase in halibut bycatch in the fall Gulf of Alaska cod fishery. This was due to an increase in halibut abundance around Kodiak and regulations intended to protect sea lions. While cod fishing is best in the winter and spring when the fish are tightly schooled, part of their season was shifted to the fall so it would not interfere with sea lion feeding. In the fall, however, the cod are dispersed, resulting in longer tows and increased bycatch rates of halibut.

These high bycatch rates resulted in premature closures for the fall trawl fishery in recent years resulting in less cod, sole and flounder across the dock. That’s why the Kodiakbased Alaska Dragger’s Association asked MCAF to work with them on a device that would exclude a significant amount of the halibut while retaining most of the cod. And since Gulf vessels have limited deck space, the device must be flexible enough to be wound about a net reel.

Gauvin enlisted the assistance of Dr. Craig Rose of the Alaska Fisheries Science Center who has used underwater video to study fish behavior in trawls. Based on his observations, Dr. Rose suggested that halibut might be able to escape through slots placed in the side of the trawl while market sized cod would still be retained. A preliminary design used slot panels made from fiberglass rods, but fishermen thought these rods were too rigid to be wound on a net reel. Instead, they suggested using electrical cable known as “third wire” that is flexible enough to be wound around the net roller but would remain rigid under the tension of being towed. John McCarthy, captain of the Kodiak trawler Pacific Star, and Mirek Lenda, a Kodiak net manufacturer came up with a way to utilize the scrap wire by lashing it into sturdy slotted panels. This achieved the concept originally conceived by Dr. Rose while being practical for everyday fishing conditions.

Using an exempted fishery permit intended for such experimental work, both designs were tested in the fall of 2006. The testing compared catch rates from two vessels doing “paired” towing: one boat using the excluder and the other without to act as a control. A total of 14 pairs of tows were made, but worsening fall weather cut the experiment short. The initial results were positive but not as good as hoped for so Gauvin, Rose and Kodiak fishermen went back to the drawing board. Video from the fall test fishery indicated water flow through the excluder was too fast for some halibut to escape. So a “gauntlet” was designed using floats to slow the water and create an area within the net where the fish can mill around while trying to escape.

Testing of the modified excluder resumed this April on Portlock Bank northeast of Kodiak. Under more favorable conditions, the test boats completed most of the 45 paired tows needed for the experimental design. Based on a preliminary look at the data, the excluder shows a consistent reduction in halibut bycatch of about 50 percent with higher halibut escapement on tows with large cod catches. Underwater video shows halibut and cod utilizing the modified portion of the excluder in the manner researchers expected.

“That’s a significant reduction in the halibut bycatch which shows the design has a lot of promise,” Gauvin said. “Despite the 20-30 percent reduction in the catch of cod, these appear to be mostly the undersized cod, although some larger cod are managing to find their way out of the excluder. With additional work on the excluder, we think that we may be able to reduce the loss of the larger cod.”

Gauvin noted more work is needed to test and fine tune the design before it can be widely adopted by the fleet. He thanked Dr. Rose for his assistance with the gear design and testing, and especially for the loaned underwater video equipment and technical assistance so fish behavior could be observed during the test. “Video is the key to learning how to improve the excluder design in the future,” Gauvin said. The researchers also thanked the captains and crews of the Kodiak-based fishing vessels Topaz, New Life, Caravelle and Pacific Star for their hard work and for their willingness to provide ideas for further development of the excluder and Katy McGauley for her field management during the project.

“This is a great example of how cooperative research works – solving problems by getting fishermen, industry and scientists together,” Gauvin said. “We anticipate even greater success in the future from a continuing exchange of ideas between Kodiak fishermen and the researchers.” The MCA Foundation is the non-profit arm of the Marine Conservation Alliance, a Juneau-based fishing industry trade association that works to find practical, workable solutions to boost the sustainability of Alaska fisheries. Members of the MCA and MCAF include fishermen, vessel owners and processors involved in the Gulf of Alaska and Bering Sea fisheries, as well as Alaska coastal fishing communities dependent on healthy fisheries. http://www.mcafoundation.org/

John Gauvin | EurekAlert!
Further information:
http://www.mcafoundation.org/
http://www.seanet.com

More articles from Ecology, The Environment and Conservation:

nachricht Dune ecosystem modelling
23.06.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

nachricht Understanding animal social networks can aid wildlife conservation
23.06.2017 | 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: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>