COMMERCE
Subscriber Services
Classified Ads
Subscribe
Advertise
NEWS
This Month
Editorial
Letters
F/V Safety
Past Issues
ABOUT US
Contact Us
Latest Issue
Subscribe
History
MORE CONTENT
CFN Archives
Links
Each month exclusively in the PRINT edition of CFN
Along the Coast
Ask the Lobster Doc
Bearin’s
Classifieds
Coming Events
Editorial
Enforcement Report
FISH SAFE
Fleet Additions
Letters
Lobster Market Report
New Boats
News Catch
Quahog Market Report
|
Commercial Fisheries News
Volume 33 Number 1
September 2005
Cage study shows yellowtail tagging mortality is low
WOODS HOLE, MA – Yellowtail flounder don’t appear to be unduly stressed by tagging. A new study this summer showed that only two percent of the fish tagged with plastic circular disks died as a result of the process.
That’s an extremely low rate for any tagging study.
“It’s saying that all of the protocols we developed have been successful,” said Steve Cadrin of the Northeast Fisheries Science Center, which heads up the yellowtail tagging work.
Biologists and fishermen, who were initially worried about potential fish stress, teamed up last year. They designed a study, which was funded by the Northeast Consortium for 2005, to investigate whether tagging-induced mortality was actually occurring.
Using specially built 6'x2' traps, the work began in June aboard the Hampton, NH-based Ellen Diane, which is owned and operated by Dave Goethel. One cage was equipped with a Hydrolab to monitor water quality.
The crew made short tows to catch yellowtail in Ipswich Bay. Fifteen untagged fish and 15 tagged fish were placed in each of three cages, explained Azure Westwood, who coordinates the tagging trips. The cages were lowered to the bottom and then hauled back up three or four days later.
During a one-and-a-half-week period in mid-June, the three cages were each used four times in four separate rounds of testings from the Ellen Diane.
Results
A storm kicked up during the second deployment and dragged the cages. Six fish died as a result. Caged fish also suffered from sand flea predation.
Despite all that, only 15 of the 360 caged fish died during the study period, and more control fish died than tagged fish.
In a report to the Northeast Consortium, which provided funding for the project, Cadrin wrote, “It appears that the trawl-capture and caging system impose more mortality than tagging.”
The work proved to be extremely useful, and for future purposes, Cadrin said biologists will assume a two percent tagging mortality rate.
“Now we can plug that into the equation and say, ‘We’re losing two percent right off the bat,’” he said.
Cadrin said he was initially “wary” of the cage study. Not only did he expect the project to be time consuming, he feared deploying and retrieving the cages would be difficult.
He was wrong. The crew handled the cages with ease, and the whole operation was pretty slick – so slick, in fact, that the tagging team decided to conduct another single round of cage work aboard the New Bedford-based Sao Paulo in July on Georges Bank.
Conditions offshore turned out to be a bit rougher, and one cage was lost due to current and tidal activity. But the two retrieved cages, just like in the Ellen Diane work, showed very low tag-induced mortality.
“This was a real eye opener to me,” said Cadrin. “It illustrates the strengths of cooperative research. The fishermen really contributed their expertise.”
Janice M. Plante
Back to story list
|
|
Tell us what you think.
