A first-of-its-kind study of bigeye tuna movements in the northwestern Atlantic Ocean led by Molly Lutcavage, director of the Large Pelagics Research Center at the University of Massachusetts Amherst, found among other things that these fish cover a wide geographical range with pronounced north-south movements from Georges Bank to the Brazilian shelf, and they favor a high-use area off Cape Hatteras southwest of Bermuda for foraging.
This NOAA-funded research, which used a new approach to study one of the most important commercial tuna species in the Atlantic, provides the longest available fishery-independent record of bigeye tuna movements to date. Data should help researchers to further characterize habitat use and assess the need for more monitoring in high-catch areas.
Results appear this week in an early online edition of the Canadian Journal of Fisheries and Aquatic Science.
Fisheries oceanographer Lutcavage says, “Although Atlantic bigeye tuna are delivering high prices to the U.S. commercial fleet and are highly sought by recreational fishermen and fishing tournaments, there’s been a surprising lack of scientific research on this species.
And in contrast to the Pacific, where tuna fisheries programs have deployed over 400,000 tags over 25 years, the Atlantic lacks the fisheries infrastructure that would increase the odds of recovering tags. We have to rely on popup satellite tags that are fishery independent to make sure we get information back from the tuna.”
Two earlier electronic tagging studies by others yielded relatively short tracking data, 113 days or fewer, and did not allow for seasonal analysis of movement or exploration of an alternate stock composition hypotheses, Lutcavage and colleagues note. Bigeye are currently managed as a single Atlantic stock, she explains, and the greater resolution of habitat use and migratory behavior revealed in this study are important first steps towards determining whether or not a more complex management approach may be warranted.
Working with pelagic longline vessel captains Scott Drabinowicz and John Caldwell of the FV Eagle Eye II out of Fairhaven, Mass., Lutcavage, with LPRC colleagues Tim Lam and doctoral candidate Ben Galuardi, deployed 21 pop-up satellite archival tags (PSAT) on adult bigeye tuna between 2008 and 2010 in the northwest Atlantic.
The sea captains fit tags on fish in good condition and return them to the sea. The PSATs were programmed to record relative light level, temperature and pressure (depth) every two minutes for eight or 12 months.
Lutcavage, Lam and Galuardi were able to collect full-resolution time series data from a total of nine tags, providing data ranging from one to 292 days. The team also downloaded remote sensing and climatological information from the NOAA to characterize possible associations between bigeye tuna movement and behavior and environmental factors.
Among variables they analyzed were the bigeyes’ use of the deep scattering layer for foraging. That is an ocean layer of marine life that rises and falls in relation to diurnal vertical migration. The researchers also looked at lunar influences on swimming depth, horizontal movements, plus vertical activity and factors influencing it such as temperature.
Lam explains, “Bigeye tuna dive deeply, like clockwork, at dusk and dawn, making it hard to use light-based geolocation methods to estimate their daily locations. Here, we showcase a new positioning technique to get around the problem of low light levels at depth by using temperature and the bigeyes’ spatial ecology and movements in the western Atlantic. But there’s much more to learn.”
The authors hope their results will inform the International Commission for the Conservation of Atlantic Tuna’s upcoming tagging effort and assist ICCAT scientists as they plan new research to better understand the population.
Alain Fonteneau, an emeritus scientist at France’s Institut de Recherches pour le Développement and a recognized expert member of scientific panels that manage regional tuna fisheries worldwide, called this work “fantastic.” He says, “Although we don’t see major unexpected surprises in these results, as we often see with Atlantic bluefin tuna results, this paper is the first one in the scientific literature to provide very new and very interesting results on bigeye vertical and geographical movements in the western Atlantic,” he points out.
Fonteneau adds, “Although these real observations are based on a small number of PSAT tags, they are much more comprehensive than the traditional catch-and-effort fishery data, at one time the only type available to ICCAT tuna scientists. It would clearly be of major scientific interest to develop this type of work at the scale of the entire Atlantic Ocean.”
Janet Lathrop | Eurek Alert!
A sudden drop in outdoor temperature increases the risk of respiratory infections
11.01.2017 | University of Gothenburg
Urbanization to convert 300,000 km2 of prime croplands
27.12.2016 | Mercator Research Institute on Global Commons and Climate Change (MCC) gGmbH
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
UMD, NOAA collaboration demonstrates suitability of in-orbit datasets for weather satellite calibration
"Traffic and weather, together on the hour!" blasts your local radio station, while your smartphone knows the weather halfway across the world. A network of...
Fiber-reinforced plastics (FRP) are frequently used in the aeronautic and automobile industry. However, the repair of workpieces made of these composite materials is often less profitable than exchanging the part. In order to increase the lifetime of FRP parts and to make them more eco-efficient, the Laser Zentrum Hannover e.V. (LZH) and the Apodius GmbH want to combine a new measuring device for fiber layer orientation with an innovative laser-based repair process.
Defects in FRP pieces may be production or operation-related. Whether or not repair is cost-effective depends on the geometry of the defective area, the tools...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
16.01.2017 | Power and Electrical Engineering
16.01.2017 | Information Technology
16.01.2017 | Power and Electrical Engineering