Fish including Atlantic cod, haddock, yellowtail flounder, striped bass and bluefin tuna have been tagged using various types of technologies to learn about their populations and movements. At the symposium, researchers presented information garnered from simple catch-and-release methods to more advanced electronic tagging techniques.
The first keynote speaker was David Welch from the Kintama Research Corporation in British Columbia, Canada. Welch spoke about the Pacific Ocean Shelf Tracking (POST) array, a highly advanced fish tracking system. POST relies on a number of wireless platforms deployed in the waters near Vancouver Island, along the coast of Alaska and into some rivers of the western U.S. The platforms are receivers for the signals from electronic tags inserted in fish such as salmon and dogfish. As fish with these tags swim near the receivers, the date, time and tag number are recorded.
“It’s like a fish EZ pass,” Welch said. “This is a tracking system that’s so good, we can learn exactly which fish from a certain release point are moving through an area.”
The Pacific populations of economically valuable fish including black cod and salmon are expected to benefit from these technologies. The POST array data have already helped to improve population models. For example, population models developed by the Canadian government and industry were previously at odds with each other, Welch explained. One denoted black cod populations were increasing, while the other showed decreasing populations. Once the detailed movement data was presented, the model was then regenerated jointly and has led to positive impacts on the model accuracy.
“When you can do experiments like this directly in the ocean, it helps to move science forward much faster than more traditional studies,” Welch added.
This tracking system is extremely expensive, Welch admitted, but by balancing data needs with financial constraints, it’s possible to find an optimal solution.
“We try to minimize cost while maximizing the biological information we receive and maximizing equipment lifespan,” Welch explained.
The other speakers for the symposium’s morning session discussed how fish species are being tracked to improve their stock assessments. Using mark-recapture studies with simple tags, researchers have learned about the mortality rates and movements of striped bass, yellowfin tuna and Atlantic cod in the western Atlantic Ocean. Thanks to the years of tagging efforts by fishermen and researchers, fishery managers will be able to develop more accurate population estimates to protect and enhance stocks of various species.
Ten posters were also presented at the lunch break, covering topics such as the movement patterns of lobsters, winter flounder and monkfish, as well as tag reporting efforts and data collected from different tag types.
Molly Lutcavage, director of the Large Pelagics Research Center (LPRC) at UNH, was the symposium’ second keynote speaker. She kicked off the afternoon session with a presentation on bluefin tuna movements in the Atlantic.
Electronic tags, particularly popup satellite tags, have been essential in determining the movements of bluefin tuna. The tags estimate geolocations of the fish based on the angle of the sunlight. Some of the initial problems associated with light-based geolocation, including light attenuating errors in the data, are currently being resolved to provide a more accurate picture of the tuna movements, Lutcavage explained. Overall, these tags have provided a wealth of information regarding migration patterns of this species.
Some of the more recent findings from the electronic tags show that bluefin seem to be homing to a forage ground near Nova Scotia, Lutcavage said. In addition, the LPRC recently began a program called “Tag a Tiny” to learn about the movements and associated thermal gradients of juvenile bluefin tunas. Tagged fish as young as three to five years old have been found crossing the Atlantic Ocean.
“Without electronic tags, there would be no way we’d figure out bluefin tunas have such diverse dispersal patterns,” Lutcavage said.
The speakers for the afternoon session covered the use of tagging studies in locations closed to commercial fishing. In particular, researchers wanted to learn if fish used these closed areas as a “safe zone” by staying inside the boundaries. While some closed areas seemed to lack an obvious pattern of fish movement, areas such as the Western Gulf of Maine closure area seemed to have areas where fish frequently traveled the same routes. In particular, one researcher described a “haddock highway” where fish travel one direction in the closed area, turn around once they reached the boundary, then travel the same route back where they originally came from.
Tom Nies from the New England Fishery Management Council also weighed in with his perspective on why data from tagging studies are important in determining fishery management plans.
“Tagging studies are helping to get at the root of the situation, and the answers they provide will only help improve our understanding of the fish populations,” Nies said.
The symposium was funded by NOAA Fisheries, NH Sea Grant, the Northeast Consortium and several fish tag manufacturers. – story by Rebecca Zeiber, NH Sea Grant Science Writer |
