Scientists Fish for More Accurate Count
By Becky W. Evans, Standard-Times Staff Writer
Fisheries scientists have teamed up with local groundfishermen to get a more accurate measure of the yellowtail flounder swimming in the popular fishing grounds of Georges Bank.
Depleted yellowtail flounder stocks drive fishing regulations for both the city’s scallop and groundfishing fleets, making it important for regulators to have the best information available on the size of the yellowtail population.
Groundfishermen, who are struggling in the face of strict catch limits and increasing cuts to fishing days designed to rebuild overfished stocks, believe the Georges Bank yellowtail stock may be larger than current estimates show.
To test whether they are right, scientists from the UMass Dartmouth School for Marine Science and Technology and the National Oceanic and Atmospheric Administration Fisheries Service’s Northeast Fisheries Science Center have embarked on a 10-day trip aboard five New Bedford draggers. On Monday, they steamed out to the southern end of the fishing grounds, known as Closed Area II, where 80 percent of the Georges Bank yellowtail stock is known to gather at this time of year.
Current fish stock estimates are based on port sampling and bi-annual trawl surveys conducted on a NOAA research vessel. While at sea this week, scientists and fishermen will measure the abundance of yellowtail using an alternative method that involves catching, tagging, releasing and re-catching the flat, bottom-dwelling fish. The method could result in more precise estimates, said Brian Rothschild, an SMAST fisheries scientist who chairs the Mayor’s Oceans and Fisheries Council.
“There is a lot at stake with regard to yellowtail, so it makes a lot of sense to maximize the amount of information you have on it,” he said.
In addition to the yellowtail study, SMAST scientists are also working with the scallop industry this week on a video survey of scallop grounds in Closed Area II and the Great South Channel.
“There’s two different surveys going on,” said Kevin Stokesbury, SMAST professor and chairman of the school’s Department of Fisheries Oceanography. “Both of them are a big deal.”
The city’s scallop and groundfishing fleets face annual restrictions on how much yellowtail they catch intentionally or by accident. The restrictions are based on the abundance of the stock. Once the yellowtail catch limit is reached, vessels are shut out of Closed Area II and unable to harvest the remaining scallops, haddock and other fish.
“The important point is that yellowtail appears to be driving the bus,” Dr. Rothschild said. “If you catch too much yellowtail, it constrains fisheries for cod and scallops.”
If the scientists find that the size of the Georges Bank yellowtail stock is larger than previous estimates show, it is possible that restrictions could ease for fishermen.
“That’s the point of doing the study,” Dr. Rothschild said.
He explained that the alternative method of estimating stock abundance is like counting fish in a swimming pool. First, you catch a group of fish and tag them. Then you throw them back in the pool and let them mix with the untagged fish. Next, you catch another group of fish. The ratio between the number of untagged fish and the number of tagged fish in the net can be used to calculate the total number of fish in the swimming pool.
“What we are looking for is some way to tell how many animals are in an area with a certain amount of confidence,” Dr. Stokesbury said.
The New Bedford draggers involved in the study are the Trident, Blue Seas, Sao Paulo, Luis and Virginia Sands. Each vessel is being paid $5,000 per day to cover the cost of fuel, food and crew’s salaries, said David Martins, an SMAST fisheries biology technician who went on the trip. Funding for both the yellowtail and scallop studies comes from a congressional earmark.
The collaboration between scientists and fishermen is essential to fisheries research, Mr. Martins said.
“Fishermen have expertise on where we’ll find the yellowtail.”
Contact Becky W. Evans at firstname.lastname@example.org
June 06, 2008
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Scientists Fish for More Accurate Count