Groundfish Data Collected with Mismarked Gear Stand Up in Statistical Analysis -- October 25, 2002 2002/10/25 Groundfish Data Stand Up in Statistical Analysis




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Report Also Confirms

Groundfish Stocks and Landings

Gain Under Rebuilding Plan









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Teri Frady
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NER NR02-13
NOAA 02-R147

NMFS Northeast Fisheries Science Center

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Woods Hole, Mass. -- NOAA Fisheries’ Northeast Fisheries Science Center issued initial research results today indicating that groundfish data collected during 2000 and 2001 using improperly marked trawl survey gear are not detectably different from similar data collected during other years, when subjected to exhaustive statistical analyses. The report also documents groundfish stock gains in the region. The National Oceanic and Atmospheric Administration (NOAA) is an agency of the U.S. Department of Commerce.

“These are the first analyses we have completed, but we are not finished investigating this problem,” said NOAA Fisheries Director William T. Hogarth. “Although we did not find quantitative evidence of a problem with our data, we know very well how important these results are to the fishing industry and the public, and that we need to build confidence. In fact, we are undertaking experiments next week that will further evaluate changes that may have occurred in survey catch because of the gear problem or other factors. We will continue to work with the fishing industry to investigate the gear problem so long as there are avenues to pursue.”

Today’s report reflects findings from a workshop composed of fishery scientists from the Northeast Fisheries Science Center, Canada, the State of Massachusetts and from the Center for Independent Experts, held in Woods Hole, Mass., Oct. 8-11. These initial results and future findings will continue to be subject to independent review and verification.

In addition to updating groundfish advice, the scientists conducted 10 different statistical analyses to detect evidence of any influence on survey data that could be attributed to the gear problem. They also conducted analyses to determine how much assessment advice would change if survey catches for the years in question were larger. These tests resulted in virtually no change in management advice for groundfish. After evaluating the results of these analyses, the group unanimously endorsed using the actual survey catch data for 2000 and 2001 in providing advice to managers.

These analyses were conducted in response to a directive from retired Navy Vice Adm. Conrad C. Lautenbacher, Ph.D., undersecretary of commerce for oceans and atmosphere and NOAA administrator, which was issued after the discovery of a gear problem on the NOAA Ship Albatross IV. In 2000, the cable used to deploy and haul back the survey-trawl net on the ship was replaced. Marks on the cable that indicate 50 meter intervals were examined in early September and found not to be accurate. The mismarking caused some tows to be deployed with more cable out on one side of the net than the other. The gear configuration affected eight resource surveys conducted between the winter of 2000 and the spring of 2002.

“We looked at existing survey data in a variety of ways and could find no signal attributed to the gear problem that would suggest catches should have been different than they were,” said Dr. Chris Darby, a scientist at the Centre for Environment, Fisheries, and Aquaculture Science, a government laboratory in the United Kingdom that participated in the meeting as an independent expert. “The survey conducts nearly a thousand tows per year, in three seasons, over the entire northeast continental shelf, under all kinds of conditions. The evidence to date indicates that the cable offset falls within the range of variability routinely encountered.”

The report also updates the status of groundfish stocks for the region, and concludes that fishing effort is higher than the long-term sustainable rate for about half of the 20 stocks that were updated. Biomasses for seven stocks are 50 percent or more of the way toward rebuilt status. Since 1995, when fish-stock rebuilding efforts first began in earnest, 19 of the 20 stocks have shown improvement with a median stock size increase of 177 percent.

“These results show that progress is being made and rebuilding works,” said Hogarth. “Between 1995 and 2001, overall groundfish mortality rates fell significantly, while landings increased by 40 percent. Most of that increase can be attributed to four stocks on Georges Bank, where rebuilding has been most successful.”

The fish stock update report issued today reflects the findings of the Groundfish Assessment Review Meeting. The peer-review panel was organized by NOAA Fisheries’ Northeast Fisheries Science Center. The report can be accessed here.

The Center also issued a related report, that of a workshop held in Woods Hole on October 2 and 3 to evaluate trawl gear performance and review the results of a cruise undertaken in late September to observe changes in the trawl gear when the cables were offset. Results of the workshop and many of its presentation were posted immediately. Today’s posting is the full report. The Report of the Trawl Warp Effects on Fishing Gear Performance Workshop can be accessed here.

NOAA Fisheries is dedicated to protecting and preserving our nation’s living marine resources through scientific research, management, enforcement, and the conservation of marine mammals and other protected marine species and their habitat. To learn more about NOAA Fisheries, please visit http://www.nmfs.noaa.gov.



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(File Modified Nov. 24 2004)